TOPIC 6: REPRODUCTION | BIOLOGY FORM 3

TOPIC 6: REPRODUCTION | BIOLOGY FORM 3

Concept of Reproduction

Reproduction is the process by which organisms g` ive rise to new members that are similar to their parents.

IMPORTANCE OF REPRODUCTION

Reproduction is an important process because;

(i) It ensures the continuity of the species.

(ii) It is a means of passage of characters from one generation to another

(iii)It increasing and maintaining population size

(iv) Sexual reproduction is a means of genetic variation among individuals

TYPES OF REPRODUCTION

There are two types of reproduction

i) Sexual reproduction

ii) Asexual reproduction

SEXUAL REPRODUCTION

Sexual reproduction involves fusion of male and female gametes in the process of fertilization.

GAMETES

Are male and female reproduction cells.

Male gamete is called sperm

Female gamete is called ovum or egg

These two gametes differ in form and function and each is produced from a different organ.

In animals the gametes producing organs are called gonads. These include the ovaries and testes.

In flowering plant structures concerned with the production of gametes are the ovaries and anthers.

The testes and anthers produce the male gametes while ovaries produce the female gametes.

FERTILIZATION

Is the fusion of male and female gametes to form zygote.

Types of fertilization

There are two types of fertilization

i. External fertilization

ii. Internal fertilization

i. External fertilization

Is the type of fertilization takes place outside the body of the female

Example of organisms that show external fertilization

> Frogs

> Some fish

ii. Internal fertilization

Is the fertilization takes place inside the body of the female.

Example of organisms that show internal fertilization

> Mammals

> Birds

> Reptiles

ZYGOTE

Is a fertilized Ovum which eventually develops into a new organism

HERMAPHRODITE ORGANISM

Is an organism which posses both male and female reproductive structures

Hermaphrodite organism is also known as Bisexual organism

CHARACTERISTICS OF SEXUAL REPRODUCTION

The following are the main characteristics of sexual reproduction:

(i) It always involves two parents, a male and a female parents

(ii) The parents must produce gametes.

(iii) Normally neither a male gamete nor a female gamete can develop into a new organism.

ADVANTAGES (MERITS) OF SEXUAL REPRODUCTION

i. It brings about variation among living organism of the same species and therefore the undesirable character cannot pass from one generation to another.

ii. It produces individual that grow slowly, hence cannot result into competition and overpopulation.

iii. Due to combination of factors from the two parents, the organism may develop resistance to diseases and hence reducing the chance of wiping the whole population.

DISADVANTAGES (DEMERITS) OF SEXUAL REPRODUCTION

i. It involves fertilization and pollination which are energy consuming process.

ii. Offspring takes a long time to mature.

iii. It involves two parents, hence cannot take place in the absence of the second parent.

iv. Since it brings variation among organism of the same species, hence the desirable characters cannot be maintained.

ASEXUAL REPRODUCTION

Isa type of reproduction in which new individualsare reproduced from a single parent without the formation of gametes.

There is no fusion of gametes butan individual separates itself from the parent and grows into a similar individual.

In this kind of reproduction, in some organisms, body part such as roots, stems or leaves may become reproductive body organs.

Examples of organisms that reproduce asexually:

> Amoeba

> Bacteria.

> Some plants

CHARACTERISTICS OF ASEXUAL REPRODUCTION

i. It involves only one parent.

ii. It does not involve the fusion of gametes.

iii. Desirable characteristics are maintained

iv. No change of genetic materials passed from a parent to an offspring since asexual reproduction involves only one individual organism.

ADVANTAGES (MERITS) OF ASEXUAL REPRODUCTION

i. It has a faster rate of reproduction.

ii. Nutrients are provided by parents, thus increasing the chances of survival of the offsprings.

iii. Beneficial characteristic of parents such as resistance to disease and high yield are maintained in their offsprings

iv. It involves only one parent and therefore no need of looking for another parent for producing a new individual.

v. It does not involve pollination and fertilization and therefore saves the energy loss.

vi. Its offspring matures faster than sexually reproduced organisms

DISADVANTAGES (DEMERITS) OF ASEXUAL REPRODUCTION

i. Organisms maintain their genetic materials, therefore there is no variation.

ii. Undesirable characteristics such as low yield and vulnerability to diseases are passed on to the offsprings.

iii. Rapid rate of growth of the organisms could deplete resources such as nutrients because of competition.

DIFFERENCES BETWEEN SEXUAL AND ASEXUAL REPRODUCTION

FORMS OF ASEXUAL REPRODUCTION

There are various forms of asexual reproduction in which includes:-

a) Fission

b) Spore formation(Sporulation)

c) Budding

d) Fragmentation

e) Vegetative propagation.

(a) FISSION

Is a type of asexual reproduction in which an organism divides into two or more parts of equal size

Fission is the simplest form of asexual reproduction.

TYPES OF FISSION

Fission is divided into two categories, namely:-

i. Binary fission

ii. Multiple fission

(i) BINARY FISSION (SPLITTING)

Is a type of fission in which an organism divides into only two equal parts to form two complete organisms.

Example of organisms which reproduce by binary fission:-
> Amoeba

> Bacteria

> Paramecium

> Euglena

Process on how binary fission occurs

i. Mother cell expands, nucleus divide into two equal parts through mitosis

(a) Mother cell               (b) Nucleus divided into two equal parts

ii. The cytoplasm separates and each part forms a cell membrane and become a new organism.

(c) Mother cell dividing           (d) Two daughter cells

(ii) MULTIPLE FISSION

Is a type of fission in which an organism divides into several parts.

Example of organisms which reproduce by multiple fission

> Plasmodium

> Parasitic protoctists

BUDDING

Is a type of asexual reproduction in which a new organism is derived from an outgrowth (bud) thatbecomes detached from the parent.

The bud later separates from the parent and grows to become an independent organism to attain the size of the parent.

Example of organisms which reproduce by budding

> Yeast

> Hydra

> Certain flatworms

> Several annelids

FRAGMENTATION

Isa form of asexual reproduction in which a parent organism breaks into two or more parts.

Fragments grow and develop into a new organism with identical features as the parent.

Example of organisms which reproduce by fragmentation
Worms such as: Nematodes (tapeworms)

Flat worms.

SPORE FORMATION(SPORULATION)

Spores are single celled bodies capable of giving rise to an individual.

The spore develops from single cell as a result of mitosis, forming a structure known as sporangium.

When the sporangium is truly developed, the wall bursts to release the spores which when placed in suitable area they germinate into new organisms.

Example of organisms which reproduce by spores

> Fungi such as mucor and rhizopus

> Bacteria

> Protozoa

> Many non-flowering plants such as ferns and mosses

 

 

 

 

 

 

Spore formation in Rhizopus

VEGETATIVE PROPAGATION

Is the form of asexual reproduction in plants where parts of the plant become detached and develop into new independent individuals

OR

Is the process whereby new individuals are formed or grow from parts of the parent plants which are not associated with reproductive organs.

Vegetative reproduction is also called vegetative reproduction

TYPES OF VEGETATIVE REPRODUCTION

There are two types of vegetative reproduction, namely:-

1. Natural vegetative reproduction.

2. Artificial vegetative reproduction.

NATURAL VEGETATIVE REPRODUCTION

Is a type of vegetative reproduction in which new plants develop from part of a parent plant such as stem, leaves or roots.

In this type, reproduction occurs without the intervention of man

Detached portions of the parent plant such as roots, leaves and stems of some plants will grow naturally and develop into new plants.

GROUPS OF NATURAL VEGETATIVE PROPAGATION

Vegetative propagation is normally grouped on the basis of the part of the plant involved. These are:

i. Propagation by modified stems

ii. Propagation roots

iii. Propagation by leaves

(i) PROPAGATION BY MODIFIED STEMS

RHIZOMES

These are horizontal underground stems with scale leaves, axillary buds, terminal buds on one end and adventitious roots.

The stem acts as a food reserve.

During favourable conditions the axillary bud develops into the aerial part of the plant.

Rhizomes are able to survive in unfavourable environmental conditions such as drought, which kills the aerial part.

Example of plants that develop rhizomes

> Ferns

> Coach grass

> Lilies

> Morning glory

STEM TUBERS

These are short swollen underground stems filled with food reserves such as starch.

Stem tubers bear scale leaves, axillary buds and lenticels.

Example of stem tubers

> Irish potatoes

STOLONS

These are slender stems that grow horizontally along the ground surface.

Stolons have terminal buds, scale leaves, nodes and internodes.

Aerial shoots and underground adventitious roots develop at the axillary buds Examples of plants that develop stolons

> Strawberries

> Oxalis

> Wandering jew

> Kikuyu grass

BULBS

These modified swollen underground shoots with thick fleshy leaves.

A longitudinal section through an onion bulb show overlapping leaves closely packed together originating from a stem.

The outer leaves are dry and scaly

They protect the inner thick, soft and fleshy leaves that containstored food

Example of bulb

An onion

CORMS

These are short swollen underground stems with stored food.

They have a flat base, axillary buds, nodes, internodes, apical buds and adventitious roots Examples of corms

> Cocoyams

> Yams

> Crocus gladiolus

> caladium

SUCKERS

These are short vertical stems, which arise from the main stem just below the ground surface.

Each sucker can separate from the mother plant and develop into an independent plant. Example of plants that develop suckers

> Bananas

> Pineapples

> Sisal

(ii) VEGETATIVE PROPAGATION BY ROOTS

These include:

Tap root

Root tubers

TAP ROOT

Is a long swollen underground root which acts as storage organs.

Examples of plants that develop tap roots

ROOT TUBERS

These are swollen adventitious underground roots.

Some of the adventitious roots swell forming underground storage organs

Root tubers do not bear leaves or bud.

Example of root tubers

> Cassava

> Sweet potatoes

(iii) VEGETATIVE PROPAGATION BY LEAVES

Leaves are not commonly used as means of propagation like stems and roots.

Several species of plant propagate vegetatively by means of leaves.

When detached from the parent plant, the leaf fall off, develops adventitious roots and bud.

These structures will develop into mature plants.

Example of plants that propagate vegetatively

> Cactus

> Begonia

> Leaf of bryophyllum

ARTIFICIAL VEGETATIVE REPRODUCTION

Is a type of vegetative reproduction where reproduction occurs with the intervention of man.

Man can learn from plants’ natural vegetative propagation and can intervene and make propagation of plants artificially.

METHODS OF ARTIFICIAL VEGETATIVE REPRODUCTION

Artificial vegetative reproduction involves the following methods:

i) Cutting

ii) Grafting

iii) Layering

I. CUTTING

In this method,a part of a plant such as a stem is cut and planted into a new place and watered.

It grows into a new complete independent plant

Example of plants reproduced by cutting

> Cassava

> Sugarcane

> Sweet potatoes

> Lemon

NB: Cassava, sugarcane and sweet potatoes are propagated by stem cuttings while lemon is propagated by root cuttings

II. GRAFTING

This method involves inserting a scion with the desired qualities into a closely related plant stock without the desired qualities.

Grafting is done commercially to get varieties of fruits like, oranges, lemons etc.

Scion is the cut shoot which is inserted into stock.

Stock is the stem onto which the scion is inserted

A figure below shows grafting method

III. LAYERING

Is the pegging down of a branch of a plant without breaking it and covering it with moist soil.  After some time the portion of the pegged branch in the soil grows adventitious roots  Once the roots are fully developed, the branch is cut off from the parent plant.

The new plant may be left to grow on its own to avoid overcrowding. Example of plants reproduced by layering

> Avocados

> Rose

> Gooseberry

Diagram showing layering method

ADVANTAGES OF VEGETATIVE PROPAGATION

i. Vegetative propagation is independent of processes of pollination, fertilization and dispersal.

ii. Fruit trees grown from seed take several years before they mature. Fruit trees grown from cutting or grafting mature in one to two seasons.

iii. New plants formed have the same genetic constitution like their parents except in cases of mutation. Any desirable characteristics of the parent will reappear in the offspring. Good qualities in parent plants are retained

iv. Vegetative propagation makes possible the propagation of plants like bananas and seedless fruits that do not have capacity for sexual reproduction. Other plants produce very small quantities of seeds and are best propagated vegetatively.

ADVANTAGES OF VEGETATIVE PROPAGATION IN AGRICULTURE

i. Offspring have the same genetic constitution like the parent plant. Therefore if the parent is susceptible to a certain disease, its occurrence may lead to destruction of the whole crop.

ii. If the parent is susceptible to a certain pest, it will be destroyed wholly.

iii. In case of unfavorable weather conditions the whole plant would be wiped off.

SAMPLE QUESTIONS

1. (a) Give the meaning of the following terms:

i. Vegetative propagation

ii. Gametes

2. Explain the merits and demerits of asexual reproduction in plants

3. Explain the merits and demerits of Vegetative propagation in agriculture.

CELL DIVISION

Is the process whereby a mature cell divides into two or more daughter cells.

Reproduction involves the multiplication of cells.

In order for cells to multiply, they undergo cell division where one cell divides into two, two to four, four into eight, and so on.

TYPES OF CELL DIVISION

Basically, there are two types of cell division, namely:

i. Meiosis

ii. Mitosis

i. MEIOSIS

Is a type of cell division that gives riseto four reproductive cells each with half number of chromosomes of the parent cell

This type of cell division, which occurs in the reproductive organs to produce sex cells known as gametes.

In this type of cell division the parent cells has diploid number of chromosomes.

However the daughter cell arising from the cell division has a haploid state.

Therefore meiosis reduces the chromosomes number into half means from 2n to n.

TERMS USED IN MEIOSIS

HAPLOID STATE

Is a condition in which the daughter cellsarising from the division have the half number of chromosomes found in the parent cell.

DIPLOID STATE

Is a condition in which chromosomes in each cell except gametes occur in pairs.

Example, in man there are 23 pairs of chromosomes in each cell (46 chromosomes).

CROSSING OVER

Is the exchange of genetic material between the homologous chromosomes.

CENTRIOLES

Are structures found in animal cells that seem to act as an orientation device during cell division.

CHROMOSOMES

Are long thread-like structures found in the nucleus of animal and plant cells.

Function of chromosomes

Carries the genes that determine an individual’s characteristics.

STRUCTURE OF THE CHROMOSOME

Chromosome is made up of two parallel strands called chromatids

Each pair of chromatids is joined at one point by a structure called centromere

Consider the diagram below showing a diagram of chromosome

CENTROMERE

Is a structure whereby each pair of chromatids joined at one point.

HOMOLOGOUS CHROMOSOMES

Are chromosomes having the same structural features and carry gene for similar characteristics in the same position

SYNAPSIS

Is the process whereby the pair of homologous chromosomes lies adjacent to each other to form bivalent.

CHIASMA (CHIASMATA)

Is the point where homologous chromosomes are joined.

It is the point at which homologous chromosomes exchange genetic materials.

STAGES OF MEOSIS

Meiosis consists of two successive divisions (meiotic division), namely:

1. Meiosis I

2. Meiosis II

NB: Both meiosis I and meiosis II progress through the stages of prophase, metaphase, anaphase and telophase.

INTERPHASE

Is the phase just before meiosis begins.

Events occur during interphase:-

i. The chromosomes appear as thin chromatin threads within the nucleus.

ii. Centrioles and mitochondria replicate.

iii. The cell grows and carries out normal life function.

Consider the diagram below showing interphase stage

NB: The interphase was wrongly named as a resting phase, but actually it is not a resting phase just because during this phase, many activities occur inside the cell like replication of cell organelles.

MEIOSIS I (FIRST MEIOTIC DIVISION)

Is the first division which involves duplication of the chromosomes and separation of the homologous chromosomes.

Meiosis I consist of the following phases:

i. Prophase I

ii. Metaphase I

iii. Anaphase I

iv. Telophase I

PROPHASE I

During prophase I the following events occur:

Chromosomes shorten, thickenand become more visible

Nucleolus disintegrate and disappear

Homologous chromosomes come together forming a bivalent. This process is called synapsis.

Chromatids cross over by chiasmata which results into exchange of genetic materials.

Consider the diagram below showing prophase I

METAPHASE I

During metaphase I the following event occur:

Spindle fibres forms

Bivalent homologous chromosomes moves to the equator of the spindle

Consider the diagram below showing metaphase I

ANAPHASE I

During anaphase I the following events occur:

i. The two homologous chromosomes separate and migrate to opposite poles of the spindle fibres.

ii. The spindle fibres attached to the centromere shorten, pulling the homologous chromosomes to the opposite poles.

Consider the diagram below showing anaphase I

TELOPHASE I

During telophase I, the following events occur:

i. The chromosomes reach their destination

ii. The spindle apparatuses breaks down and disintegrates

iii. Then the nucleus membrane reforms around each set of chromosomes

iv. The cell constricts across the membrane and divides into two Consider the diagram below showing anaphase I

QUESTION

Why first meiotic division is referred to as Reduction division?

ANSWER: Because at the end of prophase I the number of chromosomes in each cell is half the chromosomes number cell.

In animal cells before prophase II

Centrioles are replicated,

Nucleotides do not replicate since all genetic material was already formed during interphase.

This brief phase sometimes reffered to as interphase II.

BUT

In plant cells, telophase I is followed by the prophase II.

MEIOSIS II (SECOND MEIOTIC DIVISION)

Is a second division of meiosis which involves the separation of sister chromatids.

At the end of meiosis II, four daughter cells are formed from one parent cell.

The daughter cells formed at the end of meiosis II are called gametes.

Each daughter cell (gamete) has half number of chromosomes (haploid) of the parent cell.

Meiosis II progress through the following phases

i, Prophase II

ii. Metaphase II

iii. Anaphase II

iv. Telophase II

PROPHASE II

During prophase II the following events occur:

i. Centrioles replicates

ii. New spindle fibres are formed.

iii. The nucleolus disintegrates. In plant cells, the nucleolus does not disintegrate, it persists.

iv. The nuclear membrane dissolves.

Consider the diagram below showing prophase II

METAPHASE II

During prophase II the following events occur:

Chromosomes migrate to the equator of the spindle. Consider the diagram below showing metaphase II

ANAPHASE II

i. Sister chromatids separate from each other at the centromere.

ii. The spindle fibres attached to the centromere contract, pulling the sister chromatids to the opposite poles.

Consider the diagram below showing anaphase II

TELOPHASE II

(i) The chromosomes lengthen and become thin. (ii) The spindle fibres disintegrate and disappear.

(iii) The nucleolus reappears.

The nuclear membrane is formed around each set of chromosomes.

In animal cells, the cytoplasm constricts, resulting in the formation of four daughter cells, each daughter cell having the haploid number of chromosomes.

Consider the diagram below showing telophase II

In plant cells

A cell plate develops along the equator of the spindle fibres.

New cell walls are formed to enclose the four daughter cells.

In plant cells

A cell plate develops along the equator of the spindle fibres.

New cell walls are formed to enclose the four daughter cells.

A cell plate: is a structure formed from vesicles at the end of mitosis that separates the cytoplasm of two daughter cells.

DIFFERENCES BETWEEN THE MEIOSIS IN ANIMAL AND MEIOSIS IN PLANT

THE SIGNIFICANCE OF MEIOSIS IN RELATION TO REPRODUCTION

i. It helps in the formation of gametes (reproductive cells such as ova and sperms)

ii. It brings variation through crossing over action

iii. It ensures a constant number of chromosomes in organism of the same species by reducing the doubling number of chromosomes.

SIMILARITIES AND DIFFERENCES BETWEEN MITOSIS AND MEIOSIS

Similarities between mitosis and meiosis

i. Their DNA replicate once.

ii. They involve nuclear divisions.

iii. They follow through the same steps i.e. interphase, metaphase, anaphase and telophase

iv. Their homologous chromosomes align at the equator during metaphase

DIFFERENCES BETWEEN MITOSIS AND MEIOSIS

REPRODUCTION IN FLOWERING PLANTS, THE STRUCTURE OF THE FLOWER

In flowering plants (angiosperms) sexual reproduction is carried out by specialized structures known as flowers.

FLOWER

Is a reproductive organ of plant

It is a modified part of the stem or side branch in which sexual reproduction occurs

The male gametes are produced in the anthers while the female gametes are produced in the ovary

STRUCTURE AND FUNCTIONS OF A FLOWER

A flower consists of the following parts:

i. Flower stalk/pedicel

ii. Receptacle

iii. Sepals/calyx

iv. Petals/corolla

v. Stamens

vi. Pistil/Carpels

The parts of the flower are arranged in four circles called whorls and are attached to a receptacle.

DIAGRAM OF A FLOWER

I. FLOWER STALK/PEDICEL

Is the part through which the flower is attached to the stem.

Sessile flowers: are flowers which have no stalk and are directly attached to the stem of the plant

Function of flower stalk

It is the part where floral parts are attached onto it.

II. RECEPTACLE

Is a swelling that develops at the tip of the flower stalk into which the floral parts are attached in ring or whorls.

It is the axis (stem) to which the floral organs are attached

III. SEPALS (calyx)

Are the outermost parts of a flower and they are mostly green in colour.

Sepals are collectively referred to as the calyx.

Some flowers have sepal-like structures beneath the calyx known as epicalyx, for example the hibiscus flower.

Function of sepals

They protect the young flower while in the bud stage.

IV. PETALS (corolla)

Are brightly coloured leafy structures of a flower.

Petals of insect-pollinated flowers aredelicate, brightly coloured and scented.

The colour and scent attracts the agents of pollination such as birds and insects.

Petals are collectively called the corolla.

Sepals and petals are collectively referred to as the perianth.

Function of petals

(i) They attract pollinating agents such as insects and birds

(ii) They protect the reproductive organs of the flower

V. STAMENS

Are the male reproductive parts of a flower

The stamen is made up of filaments and anthers.

The male reproductive structures are collectively referred to as the androecium.

    Consider the diagram below showing male reproductive structures

VI. FILAMENT

Is a slender stalk that supports the anther.

The filament may arise from the receptacle or the petals

The filaments of some flowers are fused to form a tube-like structure called the staminal tube

Function of filament

It supports anthers

VII. ANTHER

Is a two-lobed upper part of the stem.

Each lobe has two pollen sacs within which pollen grains develop.

Pollen grains

Are the male gametesof flowering plants.

Function of anther

It produces male gametes known as pollen grains

VIII. PISTIL (Carpel)

Is the female reproductive structure of a flower.

It isthe female part of a flower

The female reproductive structures are collectively referred to as the gynoecium
Each carpel consists three parts, namely:

i. Stigma

ii. Style

iii. Ovary

Consider the diagram below showing parts of carpel

I. OVARY

Is a female reproductive organ which contains ovules.

Ovules: are unfertilized female gametes.

After fertilization ovary develops into a fruit while ovules develop into seeds

Function of ovary

It is a part where ovules are produced

TYPES OF OVARY

There are two types of ovary in relation to the position of the receptacle, namely:

1. Superior ovary

2. Inferior ovary

1. Superior ovary

Is one that is positioned above the receptacle.

Example of superior ovary

Ovary of a bean flower

Apple

2. Inferior ovary

Is one that is positioned below or enclosed within the receptacle.

Example of inferior ovary

> Ovary of Hibiscus flower

> Ovary of Rose flower

> Ovary of Black jack flower

II. STYLE

Is the hollow connecting ovary and stigma

In maize plants, the style and the stigma hang out of the flower.

Function of style

It connects the stigma to ovary.

III. STIGMA

Is a small swelling found at the tip of the style

It is glandular sticky structure at the top of the carpel.

The branches of the stigma correspond to the number of carpels.

Five branches of the stigma indicate the presence of five carpels

Function of stigma

It receives pollen grains during pollination.

NECTAR GUIDES

Are streaks of deep pigmentation (colour) originate from the bases of the petal

Function of nectar guide

Used to direct the insects to the nectarines where nectar is secreted.

Nectarines

Are swelling at the base of the petal

Function of nectarines

Produces nectar which attracts pollinating agents.

TERMS USED TO DESCRIBE DIFFERENT TYPES OF FLOWERS

1. COMPLETE FLOWER

Is a flower with all floral parts that is sepals, petals, stamens and carpels.

Example of complete flower

Hibiscus flower

2. INCOMPLETE FLOWER

Is a flower with one or more floral parts missing.

Example of incomplete flower

Clemantis

3. BISEXUAL FLOWER

Is a flower with both stamen and carpel

It is a flower with two sex (male and female sex)

Example of bisexual flower

Hibiscus flower

4. UNISEXUAL FLOWER

Is an incomplete flower with either stamens or carpel only

It is a flower with one sex only Example of unisexual flower

Pawpaw flower

5. PISTILLATE FLOWER

Is an incomplete flower that has carpels only.

It is a female flower

6. STAMINATE FLOWER

Is an incomplete flower that has stamens only.

It is a male flower

7. POLYSEPALOUS

Is a flower whose sepals are free.

8. GAMOSEPALOUS

Is a flower whose sepals are fused

9. MONOECIOUS PLANT

Is a plant in which both male and female flowers are borne Example of monoecious plant

Maize

10. DIOECIOUS PLANT

Is a plant which has male or female flowers only.

Pistillate flowers and staminate flowers are borne in different individual plants Example of dioecious plant

Pawpaw tree

11. ACTINOMORPHIC FLOWER

Is a flower that can be divided into two equal halves by any vertical section passing through the center

Actinomorphic flower is also called regular flower  It is radially symmetrical

12. ZYGOMORPHIC FLOWER

Is a flower that can be divided into two equal halves in only one particular plane passing through the center.

Zygomorphic flower is also called irregular flower  It is bilaterally symmetrical

13. INFLORESCENCE FLOWERS

Are many flowers that borne on the same branch or on closely associated branches.

Example of inflorescence flowers

> Sunflowers

QUESTIONS

1. Why the stamens and carpels are known as the essential parts of a flower?

2. Why the sepals and petals are known as the accessory parts of a flower?

ANSWER

1. Because they contain the male and female reproductive structures that play part in reproductive process.

2. Because they do not play a direct role in the reproductive process but they aid in the process by protecting the essential parts and by attracting pollinating insects

EXPERIMENT 1

Aim: to investigate the structure of a flower

Materials: Hibiscus flowers, hand lens, razor blade, a notebook.

Procedure:

1. Carefully observe the hibiscus flower you have picked.

2. Identify the different parts of the flower.

3. Describe the floral parts, noting their numbers, colour and structure.

4. Cut the flower longitudinally using a sharp new razor blade into two identical halves. Then draw a net, well labelled diagram of one half of the flower.

POLLINATION

Pollination: is the transfer of pollen grains from the anthers to the stigma of a flower.

Pollen grains from anthers are carried to the stigma by the agents of pollination such as wind, insects or birds.

TYPES OF POLLINATION

There are two mainly types of pollination, namely:

1. Self-pollination

2. Cross pollination

1. SELF POLLINATION

Is the transfer of pollen grains from the anther to the stigma of the same flower or another flower of the same plant.

Example:

Include garden peas.

2. CROSS POLLINATION

Is the transfer of pollen grains from the anther of one flower to the stigma of another flower of the same species.

OR

Is the transfer of pollen grains from the anther to the stigma of a flower of another plant but of the same species.

Example of cross pollination
Include maize.

Factors that favours cross pollination and hinder self-pollination

1. Dioecious plants: Some plants have flowers that are only male – they have only stamen. Other plants of the same species have flowers that are only female – they have only carpels.

2. Monoecious plants: Some flowers on a plant are only male and other flowers on the same plant are only female. So, self-pollination is avoided by a difference in the timing of their development.

3. Protandry: Anthers on some plants mature first. Pollination of immature stigma on the same plant is therefore not possible.

4. Protogyny: The stigmas mature first.

5. Self-incompatibility: Pollination can occur but the pollen tube doesn’t grow well, if at all, so no fertilization takes place.

DIFFERENCES BETWEEN SELF-POLLINATION AND CROSS- POLLINATION

Importance of pollination

1. It enables flowering plants to reproduce and produce enough seeds for dispersal

2. It enables flowering plants to maintain genetic diversity within a population.

3. It enables flowering plants to develop adequate fruits

4. The plants produced through pollination are more resistant to diseases.

5. It reduces chances of harmful recessive genes to express themselves,

AGENTS OF POLLINATION

Agents of pollination: are the carriers of pollen grains from the anther to the stigma.

Agents of pollination can either be organisms such as insects and birds or physical conditions such as wind and water.

THE MAIN AGENTS OF POLLINATION

The following are the main agents of pollination, namely:

i. Wind

ii. Insects

iii. Birds

I. WIND POLLINATED FLOWERS

Are flowers in which pollination occurs through wind

Wind pollinated flowers are also referred to as anemophilous flowers.

The term anemophilous is derived from the word anemo which refers to as wind.

Structure of a wind-pollinated flower (flower of rye grass plant)

ADAPTATION OF THE WIND POLLINATED FLOWERS TO THEIR MODE OF
POLLINATION

i. The anthers and stigmas are exposed to make it easy for wind to blow the pollen that can then easily land on the stigma.

ii. The pollen grains are small and light hence easily carried in the air by wind.

iii. They have smooth and dry pollen grains that can easily be picked by wind.

iv. They have large anthers which produce large amounts of pollen grains to increase the chances of pollination.

v. Their anthers are loosely attached to the filaments and hang freely to allow the anthers to be easily shaken by wind.

vi. They have a sticky stigma that traps pollen grains

vii. They have a long hairy style to expose the stigma out of the flower

viii. It has lemma that encloses the immature stamens and carpels and protects the florets of grasses.

CHARACTERISTICS OF WIND POLLINATED FLOWERS

Flowers that depend on wind for pollination have the following features:

i. They have no nectarines

ii. They are scentless.

iii. They have small petals with exposed anther and stigma.

iv. They are mostly unisexual. Example in maize, the maize cob is pistillate while the tassel is staminate.

v. They have dull- coloured petals that do not attract insects and birds.

vi. They have long, hairy style to expose the stigma outside the flower.

vii. They have large anthers which produce large amounts of pollen grains.

viii. The pollen grains are small and light. Hence easily carried in the air by wind.

ix. They have large feathery stigmas outsides the flower to trap pollen grain.

x. They have smooth and dry pollen grains that can easily picked by wind.

xi. They have a sticky stigma that traps pollen grains.

II. INSECT POLLINATED FLOWERS

Are flowers in which pollination occurs through insects.

Insect pollinated flowers are also referred to as entomophilous flowers.

The term entomophilous is derived from the word entomophily which means to be carried by insects.

Example of insect pollinated flowers

> Mango flower

> Roses

CHARACTERISTICS OF INSECT POLLINATED FLOWERS

i. They have large brightly-coloured petals which attracts insects.

ii. They are scented to attract insects for pollination.

iii. They have nectarines which contain nectar.

iv. The pollen grains are large, heavy and sticky.

v. Their anthers are small in size and produce few but large pollen grains.

vii. The stigma and anther are held firmly in position within the flower.

viii. Insect pollinated flowers are mostly bisexual

DIFFERENCES BETWEEN WIND AND INSECT POLLINATED FLOWERS

CLASS WORK

1. Give the similarities between wind and insect pollinated flowers

2. Give four differences between wind and insect pollinated flowers

FERTILIZATION IN FLOWERING PLANTS

Fertilization: is the fusion of the male and female gamete nuclei to form a zygote

Fertilization in plants takes place in the embryo sac  Double fertilization is unique feature of flowering plants.

Fertilization in plant takes place slowly.

DOUBLE FERTILIZATION

Is the process by which one male nucleus fuses with the functional egg to form a diploid zygote and the other male nucleus fuses with the polar nuclei to form the primary triploid or endosperm nucleus

PROCESS OF FERTILIZATION IN FLOWERING PLANT

Pollen grains land and sticks on the stigma and germinates. A pollen tube develops from the pollen grain and grows down the style to the ovary. It obtains nourishment along the style. The tube nucleus leads the way and the generative nucleus follows close behind it. As the tube grows downwards, the generative nucleus divides by mitosis to form two male nuclei. The pollen tube breaks through the ovary wall and enters the ovule through the micropyle. The tube nucleus disintegrates giving clear way for the two male nuclei.

The male nuclei enter the embryo sac where oneof the male nuclei fuses with the egg nucleus to form a diploid zygote. The other male nucleus fuses with the two polar nuclei to form a triploid nucleus known as the primary endosperm.This is known as double fertilization.

The diagram below showing germination of the pollen grain and growth of the
pollen tube

.

STRUCTURE OF THE MATURE OVULE

Mature ovule consisting the following parts:

i. Functional female gamete– is the egg cell at the micropyle end of the ovule used in fertilization process.

ii. Synergid – are two non-functional eggs at the micropyle end and they eventually disintegrate after fertilization

iii. Antipodal cells – are the three non-functional cells at the furthest end of the micropyle and they eventually disintegrate after fertilization

iv. Polar nuclei – are two nuclei formed when one nucleus from each group moves to the centre of the embryosac

v. The funicle – is a stalk which the ovule uses to attach to the placenta on the ovary wall. (vi) Embryosac – is a cytoplasm of an ovule

THE CHANGES THAT OCCUR IN FLOWER AFTER FERTILIZATION

After fertilization, the following changes occur in flower

SEED FORMATION

After fertilization, the fertilized ovule develops into a seed

Fertilization leads to the formation of seeds

FRUIT FORMATION

After fertilization, the fertilized ovary develops into a fruit

In most cases the development of the fruit is stimulated by fertilization.

PARTHENOCAPY

Is the process by which fruits develop without fertilization taking place

Parthenocarpy fruits such as pineapples, bananas, guavas lack seeds.

EMBRYO FORMATION

After fertilization, the zygote undergoes mitosis and becomes an embryo with three parts namely, plumule, radicle and cotyledon.

FORMATION OF THE TESTA (seed coat)

After fertilization, the integuments develop into seed coat or testa.

The testa has one scar called hilum that mark the point where the ovule was attached to the placenta

The seed coat is made up of two layers

Outer seed coat (testa) – forms the hard thick testa

Inner seed coat (tergmen) – remains thin and transparent.

FUNCTIONS OF TESTA

(i) Protects the seed against dehydration, physical damage and invasion of microorganisms

(ii) Permits oxygen and water enter into the seed during germination.

FORMATION OF PERICARP

After fertilization, the ovary wall becomes the pericarp  The pericarp is often the edible layer in fruits.

The pericarp is made up of three layers namely:

Exocarp – is the outermost layer

Mesocarp – is the middle layer

(iii)Endocarp – is the inner layer

DISINTEGRATION OF THE FLORAL PARTS

After fertilization, the stamens, sepals, petals, stigma and style wither, dry up and fall off.

In some cases, some of the floral parts may become fleshy and form part of the fruit.

The fruit retains scars at the points of attachment to the pedicel and style.

TYPES OF FRUITS

Fruits are classified into three main groups, namely:

> Simple fruits

> Aggregate fruits

> Multiple fruits

REPRODUCTION IN MAMMALS

In mammals reproduction occur through an elaborate system called reproductive system

HUMAN REPRODUCTIVE SYSTEM

Is one of the body systems made up of specialized organs such as ovaries, testes and uterus.

Its role is to produce offspring.

REPRODUCTIVE ORGANS

Are specialized organsfor reproduction to take place

Example of reproductive organs

> Testes

> Ovaries

>  Uterus

> Penis

> Vagina

THE MALE REPRODUCTIVE SYSTEMS

The male mammal reproductive system consists of the following structures

i. Testes

ii. Epididymis

iii. Vas deferens

iv. Urethra

v. Penis

vi. Accessory glands

vii. Scrotum

viii. Seminiferous tubules

 

 

 

 

THE SIDE VIEW DIAGRAM OF MALE REPRODUCTIVE SYSTEM

I. TESTES (singular: Testis)

Are two oval-shaped structures that lie outside the body cavity in a special sac called scrotum

They hang outside the body cavity to ensure their temperature is lower than that of the body.

Sperm develop best at lower temperature than that of the body.

FUNCTIONS

i. They produce the male gametes (sperms)

ii. They secrete male sex hormone called testosterone.

Scrotum: is the sac that enclosesthe testes

Function of scrotum

(i) It supports and protects the testes

SEMINIFEROUS TUBULES

Are long narrow tubes in found in each testis

Seminiferous tubules are lined with cells that develop into sperms.

The cells between seminiferous tubules are referred to as interstitial cells and they secrete androgens such as testosterone.

Function of seminiferous tubules

(i) It is a site where spermatogenesis occurs.

II. EPIDIDYMIS

Is a long coiled tube that stores the sperm made in the seminiferous tubules.

One end of epididymis is attached to the testis and the other to the sperm duct.

The lining of the epididymis has cilia which propel the sperm forward.

The contraction of the walls of the epididymis also aids in the movement of sperms through the sperm the sperm duct during ejaculation.

Sperm stored in the epididymis may be reabsorbed in the body if ejaculation does not occur within four weeks.

Function of epididymis

Epididymis used to store sperms.

II. VAS DEFERENS (SPERM DUCT)

Is a duct through which semen is carried from epididymis to urethra.

The duct has a narrow lumen and muscular walls which, when they contract during ejaculation, propel sperms towards the urethra.

Function of vas deferens

It carries sperms from the epididymis to the urethra.

EJACULATORY DUCT (URETHRA)

Is a tube that directs sperms from the vas deferensout of male body

Ejaculatory duct is also called urethra

Functions of ejaculatory duct (urethra)

i. It carries sperms out of male body from the vans deferens

ii. It carries urine out of male body from the urinary bladder

PENIS

Is a copulatory organ which is used to introduce sperms into the vagina during sexual intercourse or copulation.

The penis is made of sponge tissue muscles and blood vessels.

The head of the penis is called the glans and is covered by a fold of skin, called prepuce or foreskin.

The glans contains highly sensitive sensory nerve endings.

During sexual excitement, the erectile tissue fills with blood, making the penis firm and erect.

During sexual intercourse (copulation) the erect penis is inserted into the female’s vagina. Stimulation of the sensory nerve endings results in a reflex rhythmical contraction of various tubes in the male reproductive tract, which propels semen into vagina. This process is known as ejaculation

EJACULATION

Is the process by which sperms are released into the vagina during sexual intercourse

During ejaculation, contraction of the urethra muscles propels semen out of the erect penis.

Semen is made up of sperm and fluid from various glands in the male reproductive system also referred to as seminal fluid.

Function of penis

Used to introduce sperms into female reproductive system.

ACCESSORY SEX GLANDS

These include:

(a) Cowper’s gland

(b) Prostate gland

(c) Seminal vesicles.

Accessory sex glands produce the fluid which mixes with sperms to form semen.

Function of fluid secreted by accessory sex glands

i. It provides alkaline medium for the sperm to swim in.

ii. It provides nutrients for the sperms

iii. It provides protection to the sperms.

FUNCTIONS PERFORMED BY ACCESSORY GLANDS

ADAPTATIONS OF MALE REPRODUCTIVE SYSTEM

1. Testes occur in a pair, this increase the surface area for sperm production.

2. The presences of highly coiled seminiferous tubules increase the surface area for sperm production.

3. The scrotum offers protection from mechanical damage of the testes.

4. The testes are located outside the body to provide low temperature adequate for sperm formation.

FEMALE REPRODUCTIVE SYSTEM

The female reproductive system is made up of the following organs:

i. The ovaries

ii. Fallopian tube (Oviduct)

iii. Uterus or womb

iv. Cervix

v. Vagina or birth canal

DIAGRAM OF FEMALE REPRODUCTIVE SYSTEM

FRONT VIEW SIDE VIEW

1) THE OVARIES

These are two oval-shaped cream coloured structures that lie on the lower part of the abdomen below the kidney.

Ovaries are attached to the uterus by a membrane.

Function of ovary

i. It is the organ where ova or female gametes are produced

ii. It produces female sex hormones (oestrogen and progesterone.

LAYERS OF OVARY

Each ovary has two layers, namely:

i. Outer cortex

ii. Inner medulla

AN OUTER CORTEX

This layer has follicles which give rise to ova.

Each follicle consists of an immature ovum surrounded by epithelial cells.

A girl is born with up to 400,000 immature ova but only about 400 mature.

AN INNER MEDULLA

This layer has blood capillaries, nerve fibres and smooth muscles.

2. FALLOPIAN TUBE (OVIDUCT)

Is the tubethroughwhich the ovum moves from the ovary to uterus.

Fallopian tube or oviduct is a funnel shaped opening.

Its inner lining has cilia which help to propel the ovum towards the uterus.

Fallopian tube consists finger like projections called fimbriae which used to pick the ovum during ovulation

Function of fallopian tube

i. It is the site where fertilization takes place.

ii. It passes down the ovum from the ovary to the uterus.

3. UTERUS (WOMB)

Is a chamber between the oviduct and the vagina.

It is the organ where zygote develops during pregnancy.

The lining of the uterus is called endometrium.

Endometrium thickens every month in the preparation for pregnancy but peel off if fertilization does not occur.

Function of uterus

i. It is the organ where zygote develops during pregnancy.

ii. It is a region where implantation takes place.

iii. Its walls are thick and elastic to accommodate the growing foetus.

4. CERVIX

Is the muscular ring found between uterus and vagina  It is a neck of the uterus.

It is the point where the vagina is linked to the uterus.

Functions of cervix

i. It separates the uterus from the vagina.

ii. It allows the menstrual blood to flow out of the uterus and the sperms to get into the uterus.

iii. It is narrow to ensure that the embryo does not leave the uterus before the right time.

iv. It expands to allow the baby to pass through into the vagina during birth.

v. It has mucus plug that seals it during pregnancy to prevent microorganisms from entering the uterus.

5. VAGINA

Is a muscular tubular structure that links the uterus to outside of the body.

It is also called a birth canal

It has elastic walls that stretch during sexual intercourse and during birth

The mouth of the vagina is surrounded by flaps of tissue called labia which form the external genitalia.

Function of vagina

It is a region where sperms are deposited during sexual intercourse.

6. VULVA

Is the external opening of the vagina.

It is a region containing the female external genitalia.

The walls of the vulva contain vestibule glands which release mucus when the female is sexually aroused and helps to lubricate the penis during sexual intercourse.

Parts of vulva

Vulva is made up of the following structures:

i. Labia majora

ii. Labia minora

iii. Clitoris

7. LABIA MAJORA

Is the large lips protector for the other external reproductive organs.

It contains sweat and oil-secreting glands.

After puberty are covered by hair.

8. LABIA MINORA

Is the small lips lie inside the labia majora and surrounded the openings to the vagina and urethra.

9. CLITORIS

Is the female equivalent to male penis.

It engages with blood during sexual arousal (stimulation) which makes it to erect as penis.

GAMETOGENESIS (GAMETE FORMATION)

Is the process by which reproductive cells or gametes are formed.

TYPES OF GAMETOGENESIS

There are two types of gametogenesis, namely:

(i) Spermatogenesis

(ii) Oogenesis

(i) SPERMATOGENESIS

Is the process of sperm cells formation.

Spermatogenesis occurs in the seminiferous tubules in the testes.

The outer layer of seminiferous tubules is called the germinal epithelium.

The germinal epithelium has sortoli cells at intervals.

PROCESS OF MALE GAMETE FORMATION (SPERMATOGENESIS)

The diploid germinal epithelial cells called primordial germ cells undergo mitosis to form large diploid cells called spermatogonia.

The spermatogonia enlarge to form the primary spermatocytes.

The primary spermatocytes undergo first meiotic division to form secondary spermatocytes.

The Secondary spermatocytes undergo second meiotic division to form spermatids.

The spermatids attach to sertoli cells and then undergo differentiation to form spermatozoa (mature sperm).

Consider the chart below showing the process of male gamete formation (spermatogenesis)

NB:     2n – Indicates a diploid cell     n – Indicates a haploid cell

THE SPERM

Is the male reproductive gamete. Function of the sperm

It fertilizes the ovum to form zygote

Structure of the mature sperm

The mature sperm is made up of the following parts:

1. Head

2. Neck – contains centriole

3. Middle piece

Tail NB:

The sperm head contain:

> Large nucleus

> Acrosome

The middle piece of the sperm contain

(i) Mitochondria

Consider the diagram below showing a structure of a human sperm cell

FUNCTION OF EACH PART OF THE SPERM

ADAPTATIONS OF THE SPERM

1. It has a long tail used for swimming

2. It has a large nucleus that helps the sperm cells to carry a lot of genetic information.

3. It has numerous mitochondria that help to provide enough energy needed for sperm swimming

4. It has lytic enzymes in the acrosome which help to digest the egg membrane to facilitate fertilization.

5. They are produced in large numbers to increase chances of survival.

OOGENESIS

Is the process of eggs/ova formation.

It occurs in the ovary.

The outer surface of the ovary consists of a layer of diploid cells, the germinal epithelium.

PROCESS OF FEMALE GAMETE FORMATION (OOGENESIS)

1. The diploid germinal epithelial cells called primordial germ cells undergo mitosis to form daughter cells called oogonia.

2. The oogonia enlarge to form the primary oocytes.

3. During every menstrual cycle, one of the primary oocyte undergoes first meiotic division to form haploid secondary oocyte (immature ovum) and smaller polar body. This takes place just before ovulation.

4. The secondary oocytes undergo second meiotic division to form ootid (mature ovum) and a second polar body. This takes place after the sperm penetrated the egg.

5. The polar bodies receive the half chromosomes and have no further function hence they degenerate immediately after fertilization.

Consider the chart below showing the process of female gamete formation (oogenesis)

THE EGG (OVUM)

Is female reproductive gamete

The human ovum is a large cell of about 0.1mm in diameter

Parts of the ovum

i. It has haploid large nucleus which contains genetic materials

ii. It has a large cytoplasm which contains yolk droplets.

Yolk droplets consist of food materials such as proteins and fats used to provide the embryo with nourishment during the early stages of its development.

iii. It has outer membrane called vitelline membraneandinner membrane called plasma membraneused to enclose and protect theinner parts of the ovum.

iv. It has jelly-like layer called zona pellucid above the vitelline membrane.

v. It has corona radiata beyond the zona pellucida

Diagram below shows the structure of an ovum

ADAPTATIONS OF THE EGG TO ITS FUNCTIONS

1. It secretes the chemicals which attract sperm to move towards it.

2. It has a receptor site where the sperm bind before entering the egg cells.

3. It has food reserves in the cytoplasm used during development of zygote before the placenta is formed.

4. It has microvilli which increases surface area for absorption of nutrients

DIFFERENCES BETWEEN SPERMATOZOA AND EGG CELL

DIFFERENCE BETWEEN OOGENESIS AND SPERMATOGENESIS

Qn. Summarize the similarities and differences between

i. Spermatogenesis and oogenesis

ii. Spermatozoa and an egg cell

THE PROCESSES OF OVULATION AND MENSTRUATION

OVULATION

Is the process by which the egg is released from the ovary.

Ovulation is controlled by Luteinizing Hormone (LH).

An ovum can remain in the oviduct for 72 hours from the time of their release from the ovary.

MENSTRUAL CYCLE

Is a reproductive cycle marked by the flow of blood from the uterus after a period of time.

Menstrual cycle is also called oestrus cycle.

Menstrual cycle begins on the first day of menstruation and lasts approximately 28 days.

The menstrual cycle starts after a female puberty.

The first onset of menstrual cycle is called menarche.

PHASES OF MENSTRUAL CYCLE

Menstrual cycle involves four phases, namely:

a. Healing and repair of the uterine lining

b. Ovulation

c. Thickening of the uterine lining in preparation for implantation

d. Menstruation repeats itself.

A. HEALING AND REPAIR OF THE UTERINE WALL

Events occur during this phase:

The follicle stimulating hormone from the pituitary gland stimulates the development of follicles in the ovary to Graafian follicle.

The Graafianfollicle formed starts to secrete oestrogen hormone.

The oestrogen hormone induces the healing and repair of the uterine wall after menstruation.

B. OVULATION

Events occur during this phase:

The oestrogen hormone produced by the Graafian follicle stimulates the pituitary gland to produce the luteinizing hormone (LH).

The luteinizing hormone produced by the pituitary gland causes ovulation).

The Luteinizing hormone causes the Graafian follicle to change to a yellow body called corpus luteum

C. THICKENING OF THE UTERINE WALL (ENDOMETRIUM) IN PREPARATION FOR IMPLANTATION

Events occur during this phase:

The corpus luteum produces progesterone hormone.

The progesterone causes the wall of the uterus to thicken in preparation for pregnancy.

Progesterone and oestrogen inhibit the secretion of Follicle stimulating hormone and Luteinizing hormone

If fertilization occurs progesterone hormone inhibits the production of Follicle stimulating hormone and Luteinizing hormone as a result the Graafian follicle does not develop and ovulation does not occur.

D. MENSTRUATION REPEATS ITSELF

Events occur during this phase:

If fertilization does not occur, progesterone stimulates disintegration of the corpus luteum

Disintegration of corpus luteum leads to a drop in the level of progesterone hormone

Decrease in the level of progesterone hormone causes the endometrium to disintegrate and menstruation takes place.

Menstruation in turn leads to a decrease in the concentration of oestrogen.

The inhibition of FSH and LH ceases.

The level of these hormones starts to rise and a new cycle begins.

Diagram showing menstrual cycle of 28 days

HORMONES THAT REGULATES THE MENSTRUAL CYCLE

Menstrual cycle is regulated by the following hormones:

i. Follicle stimulating hormone (FSH)

ii. Oestrogen

iii. Luteinizing hormone (LH)

iv. Progesterone

FUNCTION OF HORMONES THAT REGULATES THE MENSTRUAL CYCLE

MENSTRUATION

Is the discharge of blood and tissue debris from the uterus through the vigina.

Menstruation occurs when fertilization did not take place and it can last among 3-5 days

Menstruation is also known as menses, menstrual flow or period.

During menstruation the dead ovum together with the lining of the uterus and quantity of the blood are passed out of the body through the vagina.

MENARCHE

Is the first period or menstruation.

DYSMENORRHEA

Is the severe pain caused by the contraction of the uterine muscles during menstruation to get rid of tissue debris and the unfertilized egg.

MONOPAUSE

Is the period in woman’s life during which her menstruation becomes irregular and subsequently stops.

Menopause occurs between 45 and 55 years of age.

During menopause the ovaries stop releasing ova and producing hormones.

ENDOMETRIUM

Is the lining of the uterus

It thickens every month in the preparation for pregnancy.

FACTORS AFFECTING THE ONSET AND DURING OF MENSTRUATION

i. Diseases

ii. Stress

iii. Anxiety

iv. Drugs

v. Foods

vi. Hormonal contraceptives

COPULATION

Is the insertion of an erect penis into the vagina of the female and move back and forth.

Sperms are deposited in the upper region the vagina.

Sperms can remain alive in the oviduct up to 48 hours from the time of their deposition.

FERTILIZATION

Is the fusion of nucleus of male and female gametes to form a zygote.

It takes place in the oviduct (fallopian tube).

The time of fertilization is likely to occur is called fertile period of the woman and normally is between the 11^th and the 17^th days after menstruation.

TYPES OF FERTILIZATION

Fertilization may occur externally or internally

1. EXTERNAL FERTILIZATION

Is the type of fertilization that takes place outside the body of female animals.

Here the female animal lay eggs in water and the male sheds sperms over the laid eggs to fertilize them.

External fertilization occurs in the following animal:

i. Fish

ii. Amphibians such as frogs

2. INTERNAL FERTILIZATION

Is the type of fertilization that takes place inside the body of the female animal.

Here the sperms are deposited by the male’s penis into the female’s tube like structure called vagina.

Internal fertilization occurs in the following animals:

i. Reptiles

ii. Birds

iii. Mammals

NB: After fertilization, the fertilized egg (zygote) develops into a young one withinor outside the body of the females.

OVIPAROUS ANIMALS

Are animals in which fertilization occurs internally but the fertilized egg develops outside the female body.

OR

Oviparous animals: are animals which lay eggs

EXAMPLES OF OVIPAROUS ANIMALS

i. All birds.

ii. Most reptiles

iii. Most arthropods.

iv. Marine invertebrates

v. Some fishes

vi. Certain type of mammals e.g. Duck billed platypus.

OVIVIPAROUS ANIMALS

Are animals whose zygote develops internally but nourishes itself like zygote that develops externally.

Oviviparous female keep their zygotes in their bodies but they do not nourish them

They only offer protections.

Example of oviviparous animals includes:

i. Reptiles

ii. Some fishes

iii. Certain insects

Oviviparity: is a condition in which the zygote develops internally but nourishes itself like zygote that develops externally.

VIVIPAROUS ANIMALS

Are the animals whose zygote develops within the maternal body and gets its nourishment from maternal body.

Viviparity:Is a condition whereby a zygote develops within the maternal body and gets its nourishment from maternal body.

THE PROCESS OF FERTILIZATION AND PREGNANCY

The process of fertilization and pregnancy occur as follow:-

i. During sexual intercourse the urethra muscles in the penis contract to release semen into the vagina during ejaculation.

ii. After the sperm are deposited in the upper region of the vagina they swim through the cervix to the uterus and then enter the oviducts.

iii. After ovulation, the ovum moves into the oviduct where it fuses with the sperm to form a zygote.

iv. The zygote formed undergoes cell division to form a hollow mass of cell called a blastocyst or blastula.

v The zygote moves in the oviduct towards the uterus and is implanted in the endometrium.

vi. Cilia and contractions of the oviduct walls propel the zygote towards the uterus.

vii. This movement can take up to a week.

IMPLANTATION

Is the process by which the zygote is attached to the uterine wall.

It occurs between six to nine days after fertilization.

Implantation is completed about 11 to 12 days after conception.

THE PROCESS OF ZYGOTE IMPLANTATION

After fertilization, the formed zygote travel from the fallopian tube to the uterine wall

i. The outer cells of the zygote release hydrolytic enzymes that digest the epithelium of the uterine wall hence making a cavity on it.

ii. After formation of cavity on the uterine wall, the zygote sinks into that cavity and gets established.

iii.  After implantation is completed the zygote undergoes further cell division to form an embryo.

iv. The out layer of the embryo’s cells develops finger like projection called villi.

v. The villi extend into the lining of the uterus and form part of the placenta.

vi. After eight weeks, the embryo is called foetus.

DIAGRAM BELOW ILLUSTRATE OVULATION, FERTILIZATION AND IMPLANTATION PROCESSES

EMBRYO

Is a plant or animal as it develops from a fertilized egg.

The embryo is attached to the placenta by a tube like structure called umbilical cords.

Umbilical cord has two arteries and one vein.

FUNCTIONS OF THE UMBILICAL CORD

i. It connects the foetusto the placenta

ii. Umbilical arteries carry deoxygenated blood from the foetus to the placenta.

iii. Umbilical vein, carries blood rich in nutrients, antibodies and oxygen from the placenta to the foetus.

PLACENTA

Is a temporary organ joining the mother to the foetus in the uterus.

It is the point at which close association develops between maternal and foetal circulation.

The placenta is formed from the embryo and part of the endometrium of the uterus.

The placenta begins to carry out its functions 12 weeks after implantation.

FUNCTIONS OF PLACENTA

i. It allows carbon dioxide and nitrogenous wastes like urea to diffuse from the foetus to the mother.

ii. It allows oxygen, water, glucose, acid vitamin and mineral salt to diffuse from the mother’s blood to the foetus.

vi. It is the site of gaseous exchange between the mother and the foetus.

vii. It allows maternal and foetal blood circulation to flow in different directions. This is called counter-current flow.

viii. It allows the maternal and foetal circulation to be at different pressures.

QUESTION. Why are the maternal (mother) and fetal (foetus) blood do not allowed to mix?

Answer. Maternal and fetal blood do not mix due to the following reasons:

i. Maternal blood flows under higher pressure compared to the fetal blood, this could damage the delicate blood vessels of the foetus.

ii. If two bloods were mix, the fetal blood could be recognized as foreign by the maternal blood, hence the maternal blood immune system could respond by killing the foetus.

iii. Half of the genetic materials come from the father and so the fetal cells are not identical to those of the mother.

ADAPTATIONS OF PLACENTA TO ITS FUNCTIONS

i. It contains villi which increase the surface area over which exchange of substances takes place.

ii. Have thin membrane to reduce the distance across which exchange of substances occurs.

iii. It is rich in blood vessels to enable greater exchange of substances across the placenta.

PLACENTAL EXCHANGE

ii. Water

iii. Digested food substances e.g. Glucose

iv. Amino acids

v. Vitamins

vi. Mineral salts

Antibodies which provide protection against diseases such as tetanus, measles and small pox

i. Carbon dioxide

ii. Nitrogenous waste products e.g. urea

Material not allowed to pass through the placenta.

i. All the body cells

ii. Plasma proteins

iii. Pathogens

Layers developed after implantation.

During the process of implantation three membranes develop, namely:

a. Amnion

b. Chorion

c. Allantois

(a) AMNION

Is the membrane that enclose amniotic cavity

Function of amnion

It surrounds the embryo and creates amniotic cavity

Amniotic cavity is filled with a fluid known as amniotic fluid.

FUNCTION OF AMNIOTIC FLUID

i. Protects the embryo against shock since it is shock absorber.

ii. Protects the embryo against injury and physical damage.

iii. Keeps the embryo moist.

iv. Maintains the external temperature of the foetus.

CHORION

Is the membrane which surrounds the amnion

Function of chorion

i. It surrounds the amnion

ii. Chorion forms finger- like projections called chorion villi.

Function of chorion villi

Used to supply nutrients to the embryo.

ALLANTOIS

This membrane is present only for a short time.

Function of allantois

It removes and stores the waste products of the embryo.

NB: Allantois later becomes the umbilical cord while chorion forms the placenta.

DIAGRAM OF AN ENBRYO AND ITS PLACENTA

GESTATION

Is the period between fertilization and birth.

In humans, the gestation period is referred to as pregnancy.

Pregnancy lasts 9 months or 40 weeks in humans.

Different mammals have different gestation periods as shown in the table below

NB:

During the gestation period, the zygote develops into an embryo, then a foetus.

The heart of the human embryo starts to beat in the seventh week.

By the 26^th week, the foetus is full formed and has high chances of surviving if it is born prematurely.

CHILD BIRTH

Is the end of a pregnancy with the birth of one or more babies.

OR is the process by which the full formed foetus is expelled out from the mother’s womb after gestation period is completed.

THE PROCESS OF CHILD BIRTH

This process occurs after 9 months in human being.

Child birth starts with the rhythmic contractions of the uterine muscles.

Birth is triggered by the fall in the level of oestrogen and progesterone in the maternal blood.

The fall in the level of oestrogen and progesterone and subsequent release of oxytocin cause the periodic contractions of the muscular wall of the uterus.

The release of oxytocin occur in waves.

The uterine contractions are the ones, which cause pains known as labour pains.

Labour pains are accompanied by the dilation of the cervix, and the rapture of the amnion and chorion releasing amniotic fluid.

At this juncture uterine concentrations become frequent and powerful pushing the baby downwards, head first through the enlarged cervix and widened birth canal and the baby is born.

Immediately after birth the umbilical cord is tied (ligatured) and cut to separate the baby from the placenta.

The final stage of birth is the expulsion of the placenta as an after birth.

INDUCED BIRTH

When pregnancy lasts for more than 38 weeks or when examination shows that the placenta is not coping with the needs of the foetus, birth can be induced either by:

i. Carefully breaking the membrane of the amniotic sac.

ii. Injecting oxytocin hormone helps to rupture the amnion.

CAESARIAN DELIVERY

Is the removal of the baby by surgical means through incision of the abdominal and uterine walls.

CAESARIAN SECTION (CS)

Is an operation to remove the baby from the uterus.

Caesarian section it be carried out due the following complications:

i. Narrow birth canal (vagina)

ii. When the umbilical cord coils around the baby’s neck.  Where the mother cannot push the baby.

iii. When the baby’s head is too big

iv. If the baby is in an abnormal position.

COMPLICATIONS OF PREGNANCY

The following are complications which prevent full-term development of a foetus.

1. Ectopic pregnancy

2. Stillbirths

3. Abortion

4. Miscarriage

5. Preterm (pre- mature) babies

6. Preeclampsia

1. ECTOPIC PREGNANCY

Is a situation where the fertilized egg does not move to the uterus and is implanted in the fallopian tube

Ectopic pregnancy is caused by blockage of the fallopian tube due to infections, diseases or other factors

2. STILLBIRTHS

Is the situation where a foetus dies while still in the uterus.

OR Is the giving birth to a dead baby.

The following are possible causes of still birth

i. High blood pressure

ii. Preeclampsia

iii. Drugs

iv. Alcohol

v. Pharmaceutical drugs

vi. Bacterial infection

vii. diabetes in the mother

viii. Exposure to radiations

ix. Physical trauma and rhesus diseases.

3. ABORTION

Is the purposeful removal of the foetus from the womb before it has developed enough to survive on its own.

OR Is the removal of the foetus before it is fully developed by either physical or chemical means.

Abortion is usually done before the end of the third month or by the 24^th week of pregnancy.

TYPES OF ABORTION

There are two types of abortion

i. Spontaneous abortion

ii. Induced abortion

I. SPONTANEOUS ABORTION

This occur when the foetus is expelled from the womb without being induced in any way.

II. INDUCED ABORTION

Is the deliberate ending of pregnancy due to medical reasons.

Abortion can be carried out with the purpose of saving mother’s life if the foetus is found to be developing in an abnormal way.

4. MISCARRIAGE (spontaneous abortion)

Is the loss or termination of a pregnancy before 20-24 weeks.

It is referred to as miscarriage because the foetus is not fully developed and hence cannot survive on its own.

The first sign of a miscarriage is bleeding which sometimes associated with pain.

The following are possible causes of miscarriage
i. Poor nutrition of the mother.

ii. Exposure to chemicals

iii. Psychological trauma and medications.

iv. Uncontrolled diabetes

v. High blood pressure

vi. Cigarette smoking

v. Chromosomal abnormalities in the developing foetus.

5. PRE-TERM BABIES OR PRE- MATURE BABIES

Are those babies born before 37 weeks

Usually a baby is born after about 40 weeks.

Premature babies born with less than 2.5 kilograms, very small, weak and need special care.

Pre-mature babies must be kept in a special machine called an incubator until they can support themselves because they have difficulties in breathing, sucking and maintaining their body temperature.

6. BREECH BIRTH

Is a situation where the baby is born legs first.

Normally, babies are born head first.

PREECLAMPSIA

Is a condition of pregnancy characterized by high blood pressure and protein in the uterine.

A woman with preeclampsia experiences the following symptoms:

i. Sudden weight gain

ii. Swelling of the face and hands.

iii. Severe headache.

iv. Abdominal pain

v. Blurred vision.

If not treated, it can develop into eclampsia.

NB: Eclampsia: is a very serious condition which is characterized by seizures and if not treated may be fatal

WAYS OF MINIMIZING COMPLICATIONS OF PREGNANCY

The following are proper measures that should be taken to prevent complications of pregnancy:

1. Visiting a parental clinic as early as possible once a woman discovers that she is pregnant.

2. Improveyour nutrition and maintain a balance diet.

3. Prevent sexually transmitted diseases and cure them properly if contracted.

4. Avoid giving birth at home especially when there is no certified and qualified midwife.

FACTORS THAT HINDER FERTILIZATION

The following are the factors which may hinder fertilization:

i. Blockage of the fallopian tube

ii. Low sperm count

iii. Unhealthy gametes

iv. Use of contraceptives

v. Diseases

vi. Premature ejaculation

vii. Impotence

viii. Hormonal abnormalities

I. BLOCKAGES OF THE FALLOPIAN TUBE

Sperms do not find their way to the ovum when the fallopian tube is blocked. The blockage of fallopian tube can be caused by factors such as sexually transmitted diseases or some contraceptive methods.

II. LOW SPERM COUNT

Low sperm count minimizes the chances of fertilization, hence infertility.

Causes of low sperm count

> Excessive use of alcohol, drugs, and smoking

> Hormonal abnormities and sexually transmitted diseases.

Sperms count: is a measure of mount of sperms in a man’s ejaculate

For a man to fertilize an egg, at least 20 million sperms must be produced so as to increase the chances of fertilization.

III. UNHEALTHY GAMETES

Production of unhealthy gametes in one or both male and female that cannot be viable to form a zygote minimizes the chances of fertilization

Causes of unhealthy gametes

a. Poor health due to poor diet or disease.

b. Exposure to strong radiations

IV. USE OF CONTRACEPTIVES

Some contraceptives used by women produce thick mucus that prevents sperm from reaching the ovum.

Some even kills the sperm before reaching from the ovum.

V. DISEASES

Some diseases such as Sexually transmitted diseases block the fallopian tube or the epididymis hence blocking the sperm from reaching and fertilizing an egg.

Prostate cancer and inflammation may also hinder sperm formation hence no fertilization.

VI. PREMATURE EJACULATION

Is a situation where by a man reaches orgasm before he inserts his penis into a vagina.

Premature ejaculation prevents the sperms from getting into the female reproductive system for fertilization to occur

VII. HORMONAL ABNORMALITIES

Hormonal problems in females may hinder ovulation. When this occurs fertilization will not take place because the ovum may be immature or may not have been produced at all.

In male hormonal abnormalities may lead to low sperm count or failure to produce sperm.

VIII. IMPOTENCE

Is a condition in which a man fails to achieve an erection or achieves it but cannot maintain it.

Causes of impotence

1. Anxiety

2. Depression

3. Chronic diseases like diabetes

4. Prostate cancer.

ARIFICIAL INSEMINATION

Artificial insemination: is a technique whereby sperm from a donor is artificially inserted through the cervix of the mother-to-be.

Insemination is done in humans but more widely used in farm animals such as cattle.

IMPORTANCE OF ARTIFICIAL INSEMINATION

In humans

1. It enables couples or women whose partners cannot make them pregnant, to be able to give birth by being fertilized by sperms from a donor.

2. It enables man to preserve sperms so that their wives can conceive when they are away from home along period even after the husband dies.

3. The woman has a chance to choose the father of her child as she can select semen from different men.

In agriculture (farms)

1. It enables farmers to get desired characteristics for their animals, such as resistance to diseases or high milk production.

2. It provides a rapid means of spreading the beneficial characteristics of a particular male throughout the stock.

3. Semen can be transported far distances even where there are no males.

4. Many females can use semen from one male. For example, the semen from a single bull can be used to sire as many as 90000 cattles a year.

5. It allows cross bleeding which brings about variation.eg a Fresian cow can be mated by a Jersey bull.

TEST TUBE BABIES

Are babies whose fertilization is carried out in the test tubes by suckling the ovum from woman and sperm from man by syringe.

After fertilization to take place then the zygote is inserted into the woman’s womb where there is a chance of implantation and development of the embryo.

Woman who are unable to conceive because their fallopian tubes are blocked can use this technique.

SURROGATE MOTHER

Is a woman who allow uterus to be used to carry artificially fertilized ovum to birth.
After birth the baby is given to the woman who donated the ovum.

FERTILITY DRUGS

Are synthetic hormones administered to women who cannot conceive because their ovaries do not release ova

MULTIPLE PREGNANCIES

Multiple pregnancy: refers to a situation when more than one foetus is carried in a single pregnancy.

Multiple pregnancies result into birth of two, three, four, or up to eight offspring at a time.

CAUSES OF MULTIPLE PREGNANCIES

i. Genetic factors

ii. The use of fertility drugs – which may cause several eggs to be produced at the same time.

iii. More than one ovum released into the reproductive track

iv. One fertilized ovum splitting up into more than one embryo resulting to twins.

The terms used to describe multiple births are derived from Latin words for numbers as
follows:

1. Twins– Two offspring

2. Triplets– Three offspring

3. Quadruplets – Four offspring

4. Quintuplets – Five offspring

5. Sextuplets-Six offspring

6. Septuplets -Seven offspring

7. Octuplets – Eight offspring

The most common form of multiple pregnancies is birth of twins.

Quadruplets develop when an egg divides into two and again each half further divides into two.

More divisions my result in up to eight offspring.

TWINS

Are two babies born at the same time one after another by the same mother.

TYPES OF TWINS

There are two common types of twins, namely:

(a) Identical twins

(b) Non-identical twins or fraternal twins

(a) IDENTICAL TWINS

Are twins arise from a single fertilized egg, that splits into two parts and each part develop into a complete individual.

Identical twins are also known as uniovular twins or monozygotic twins

Characteristics of identical twins
i. They are of the same sex.

ii. They are very much alike (similar)

iii. They are genetically identical

iv. Only one sperm fertilizes the egg

v. They arise from a single egg (ovum)

vi. They are closed in the same membrane and share the same placenta.

Consider the diagram below illustrating the formation of identical twins

SIAMESE TWINS

Are identical twins who develop without separating completely and born attached to one another.

Causes of Siamese twins

i. Failure of a complete division of the zygote.

ii. It is an abnormality.

iii. The zygote starts dividing into two but stops at a point.

(b) NON-IDENTICAL TWINS

These twins develop when two eggs are released from the ovaries at the same time.

Identical twins are also called fraternal twins or binovular twins or dizygotic twins

Characteristics of fraternal twins     

i. The twins may be of the same or of different sex.

ii. Each egg is fertilized by a different sperm.

iii. The twins do not look alike.

iv. They are genetically different but have a degree of resemblance.

v. They arise from a two eggs released from the ovaries at the same time.

Consider the diagram below illustrating the formation of fraternal twins

DIFFERENCE BETWEEN IDENTICAL TWINS AND FRATERNAL TWINS.

DISORDERS OF REPRODUCTIVE SYSTEM

The following are disorders that affect both male and female reproductive systems.

1. Infertility

2. Pelvic inflammatory Disease (PID)

3. Sexual Transmitted Infections (STI’s)

4. Impotence

5. Blockage of fallopian tubes.

6. Blockage of the sperms duct,

7. Cancer

8. Congenital Malformation

9. Hormonal abnormalities

10. Vaginal discharges

11. Fibroids

12. Premature ejaculation

THE CAUSES, EFFECTS AND POSSIBLE REMEDIES (TREATMENTS) OF THE REPRODUCTIVE SYSTEM DISORDERS

1. INFERTILITY

Is the inability to conceive.

Or is the situation where a woman is unable to carry a pregnancy to full term.

Infertility can occur to both male and female.

Causes of infertility

i. Diseases. Example chlamydia, gonorrhea and syphilis cause blockage of the fallopian tubes and sperm ducts leading to infertility.

ii. Low sperm count thus reducing chance of fertilization

iii. Removal of the uterus due to cancer.

iv. Failure to ovulate because the ovaries are not producing eggs

v. Low sperm motility that is, the inability of sperms to swim and reach the eggs.

Effects of infertility

i. Failure of a couple to have children.

ii. Leads to broken marriages especially when one partner blame the other.

Possible treatment (remedies) of infertility
i. Use of medications such as fertility drugs.

ii. One can carry out an operation on blocked fallopian tubes and sperm ducts

iii. Use of artificial insemination to enable a couple have children

iv. Avoiding the risks of contracting STI’s

v. Avoiding smoking

vi. Avoiding exposure to chemicals

vi. Seeking for medical help

2. PELVIC INFLAMMATORY DISEASE (PID)

Is an infection that lead to the inflammation of the uterus, fallopian tubes and other reproductive parts.

Pelvic inflammatory diseaseoccurs in women.

Causes of pelvic inflammatory disease

Untreated STIs like gonorrhea and chlamydia in which the bacteria travel up into the uterus, oviduct, ovaries and pelvic cavity.

Effects of pelvic inflammatory disease

> Lead to blockage of the fallopian tubes hence infertility in women.

> Lead to ectopic pregnancy and chronic pelvic pain.

> Cause scars to nearby tissues and organs.

Possible treatments or remedies for pelvic inflammatory disease

(i) Pelvic inflammatory diseasecan be treated by taking antibiotics.

(ii) Abstaining from sex and practicing safe sex.

3. CANCER

Is a disease characterized by abnormal and uncontrolled growth of cells.

Cancer can occur anywhere in the body including the reproductive system.

Types of cancer which occur in the reproductive system

The following are types of cancer that affect the reproductive system

i. Prostate cancer

ii. Cancer of the testes in male

iii. Cancer of the ovaries

iv. Cancer of the uterus (uterine cancer)

v. Cervical cancer in females.

CERVICAL CANCER

Is cancer of the cervix and it attacks women.

Causes of cervical cancer

The main cause of cancer is unknown but there are factors that increase the risk of getting cancer include:

i. Risk factors such as STIs. About 80% of cervical cancer is associated with STIs

ii. Other factors such as smoking and exposure to chemicals. About 20 %of cervical cancer is associated with these factors.

Effects of cervical cancer

i. It may cause heavy, long and abnormal menstrual flow.

ii. Lead to infertility

iii. Can lead into death.

UTERINE CANCER

Is cancer of the uterus and it attacks women.

Causes of uterine cancer

i. Risk factors such as prolonged exposure to oestrogen.

ii. Early onset of menstruation

iii. Late menopause

iv. Never getting pregnant and obesity.

v. These risk factors are also associated with ovarian cancer.

Effects of uterine cancer

i. Causes strong abdominal pain.

ii. It causes heavy, long and abnormal menstrual flow.

iii. Infertility

iv. If not early can lead to death.

PROSTATE CANCER

Is the cancer of prostate gland, a gland found in male reproductive organs.

It is mostly attacks men over 50 year of age.

Causes of prostate cancer

i. Maintaining a diet high in fat and red meat

ii. Alcohol consumption

iii. Inactivity

iv. Obesity and aging.

v. Food preservatives and addictive

vi. Viruses and UV rays.

Effects of prostate cancer
i. Difficulty in erection.

ii. Surgery to remove the prostate gland may lead to permanent impotence.

iii. Problems with controlling and passing urine since the grown prostate tissue may have pressed on the urethra.

iv. Decreased sexual desire

v. Painful ejaculation

Possible remedies for cancer

i. Avoid smoking

ii. Control weight and avoid diet rich in fat and red meat.

iii. Eat balanced diet low in fat and rich in fruits, vegetables and fish.

iv. Exercise regularly

v. Regular screening at least once a month since early stages of cancer can be treated through surgery.

vi. Surgery can cure cancer completely if the cancer is found before it spreads to other organs or tissue.

4. ENDOMETRIOSIS

Is the condition whereby the tissue lining the uterus (endometrium) grows in other areas of the body.

This occurs in the tissue around the pelvic area.

Endometriosis causes a lot of pain in the abdomen, and may lead to infertility.

If not treated, can block oviducts and cause infertility.

It is important to take regular checkups and early treatment once endometriosis is discovered.

5. CONGENITAL MALFORMATION

Absence of the uterus, ovary or fallopian tube

Some women are born with blocked oviduct or with no uterus

6. FUNCTIONAL DISORDERS

Is the inability of the woman to experience sexual pleasure and satisfaction during the sexual act.

Causes of functional disorders

i. Emotional problems

ii. Feeling of guilt

iii. Trauma

SEXUALITY AND SEXUAL HEALTH AND RESPONSIBLE SEXUAL BEHAVIOUR

Sexuality

Refers to anything that has to do with being male and female.

It involves sexual orientation

Sexuality is the function of whole personality begins at birth and end at death Sexuality includes various aspects such as:

i. Being biologically male or female

ii. Having masculine or feminine behavior

iii. Sexual functioning

iv. How one is interested and experiences sexual activity  How he/she is attracted to others.

SEXUAL BEHAVIOURS

Isthe way people express their sexuality.

Types of sexual behaviour or practice

The following are types of sexual behaviour

i. Acceptable sexual behavior or responsible sexual behaviour

ii. Unacceptable sexual behavior or irresponsible behaviour

RESPONSIBLE SEXUAL BEHAVIOURS

Are sexual behaviours, which are normal and accepted in the societies.

Examples of responsible behaviours

> Marriage

> Heterosexuality

NB: Heterosexuality is the sexual practice between members of the opposite sex

> It is also called vaginal sex

IRRESPONSIBLE SEXUAL BEHAVIOURS

Are sexual behaviours which are not accepted by the family as well as societies.

Irresponsible sexual behaviors are also called sexual deviations

Examples of irresponsible sexual behaviours

i. Use of alcohol and drug abuse

ii. Prostitution

iii. Homosexuality

iv. Erotic fantasy

v Masturbation

vi. Celibacy

vii. Anal sex

viii. Oral sex

ix. Watching pornography

x. Bisexuality

xi. Rape

i. EROTIC FANTASY

Is a situation whereby a person creates imaginary thoughts like making love to an opposite partner while he/she is not.

ii. MASTURBATION

Is the sexual behaviour in which one attains sexual arousal and orgasm through self-stimulation.

The stimulation may be brought about by touching or rubbing genitals, against objects such as hand fingers, pillow or special devices.

iii. CELIBACY

Is when a person abstains continuously from sexual activity.

People may practice celibacy due to the following reasons:

i. Health problems

ii. Religious beliefs

iii. Avoiding diseases like AIDS

iv. ANAL SEX

Is a sexual practice whereby an erect penis is inserted into the anus of a man or woman.  Anal sex is also known as sodomy

v. ORAL SEX

Is a sexual practice whereby an erect penis is inserted into the mouth rather than the vagina.

Or is a sexual practice whereby lips and tongues are used to stimulate the genitals of the partner

vi. PROSTITUTION

Is the exchange of sexual services for money.

A person who practices prostitution is called a prostate.

A prostitute can be a man, woman or even children.

vii. PORNOGRAPHY

is obscene literature, art or movies that show sexual acts and images in a way that is intended to make people feel sexually excited or aroused.

Some people enjoy watching pornographic movies or magazines and get aroused and end up masturbating or having sex.

viii. HOMOSEXUALITY

Is a sexual practice between members of the same sex

Such people are called homosexuals

Male homosexuals are called gays

Female homosexuals are called lesbians

ix. BISEXUALITY

Is a sexual practice where people are sexually attracted towards members of the same sex and of the opposite sex.

Such people are called bisexuals.

x. RAPE

Is the use of force or threats to have sex with someone against his/her will.

xi. INCEST

Is a sexual practice with a close relative. E.g. father and daughter

CAUSES OF IRRESPONSIBLE SEXUAL BEHAVIOURS

i. Poverty

ii. Lack of proper counselling and guidance

iii. Peer pressure and influence

iv. Mass media

v. Moral decay

vi. Marriage breakdown

vii. Poor parenting

viii. Drug addiction

ix. Globalization and advancement of science and technology

x. Personal behavior

POVERTY

Some people may practice unaccepted sexual behavior like prostitution due to poverty. Such people practice prostitution as a source of income.

PERSONAL BEHAVIOR

Some people practice certain sexual behavior because they just enjoy doing it. For example some people practice prostitution simply because they enjoy doing it not because they need money.

LACK OF EDUCATION

Some people practice unaccepted sexual behaviours because they because they do not have the right information about sexuality.

MORAL DECAY

Due to moral degradation some people practice unacceptable sexual behaviours like rape, having sexual intercourse with relatives, parents, homosexuality, bisexuality and prostitution.

POOR PARENTING

Some peopleend up practicing unacceptable sexual behavior because they did not get proper guidance from their parents when they were younger.

GLOBALIZATION AND ADVANCEMENT OF SCIENCE AND TECHNOLOGY

Globalization has made people capable of accessing sexual practices acceptable and practiced in other countries and adopting them even though some may not be acceptable in one’s society.

EFFECTS (CONSEQUENCES) OF IRRESPONSIBLE SEXUAL BEHAVIOUR

i. Spread of sexually transmitted diseases. E.g. syphilis, HIV/AIDS, gonorrhea.

ii. Early and unexpected pregnancies.

iii. Family and marriage breakdown.

vi. Death. E.g. after a rape

vii. Getting a responsibility of caring for a family at an early age.

viii. It can degrade the personality of a person. For example, prostitutes or rapists have no place to put their faces in some societies

ix. Lead to conflict in the family or marriage

x. It leads to authorities spending so much money to treat patients who have contracted STDs.

xi. Increasing the level s of crimes.

x. Increasing illiteracy rate.

WAYS OF ERADICATING IRRESPONSIBLE SEXUAL BEHAVIOURS

The following are some measures that can be taken to prevent irresponsible sexual behaviours in the family and community:

i. Avoiding all practices that can lead to sexual excitement such as taking alcohol, watching pornography, meeting in dark and guest places.

ii. Being faithful to your partners.

iii. Impose strict government laws. E.g. against rape

iv. Following religious teachings on sexuality.

v. Offering guidance and counseling services about sexuality.

vi. Close supervision and guidance of children. E.g. protection of children from media coverage scary events such as wars, bombings, or shootings.

vii. Providing education to the people about sexuality.

viii. Controlling emotions and desires by being involved in age-appropriate activities. E.g. Sports.

FAMILY PLANNING AND COTRACEPTION

FAMILY PLANNING

Refers to taking action so that only the required numbers of babies are born.

Family planning is also called birth control

CONTRACEPTION

Refers to the prevention of pregnancy intentionally.

Importance of family planning and contraception.

The following are reasons, why family planning and contraception is very important to the mother, the family and community:

1. It allows a couple to have a baby only when they want it.

2. It allows a couple to have the number of children they are able to take care of.

3. It gives the mother time to work and carry out economic activities instead of spending their entire time caring for children.

4. It ensures parents are able to provide enough food and give the children enough attention and care such that they can grow in a healthy way.

5. It enables the mother to have enough time for her body to recover before having another baby.

6. It enables a government to have population that it can support and develop.

SOCIAL PRACTICES (METHODS) WHICH ENHANCE FAMILY PLANNING

The following are contraceptive methods which enhance family planning. These methods are grouped into two groups, namely (a) Natural methods

(b) Artificial methods.

(a) NATURAL METHODS

Are methods that is carried out without the use of device or chemicals.

The following are natural methods which enhance family planning and contraception

i. Abstinence

ii. Calendar method

iii. Withdrawal method

iv. Cervical mucus method

I. ABSTINENCE

Is where a person totally refrains from sexual intercourse.

Advantages of abstinence method

It is 100% effective

Disadvantage

It is not easy especially for married couples.

II. WITHDRAWAL METHOD

Is a method whereby the male withdraws his penis from the vagina before ejaculation.

Withdrawal method is also called coitus interrupts

Advantages of withdrawal method

> It is costless

> It is reliable when effectively carried out.

Disadvantages of withdrawal method

> There is a likelihood of sperm leakage from semen that could escape from the sperm duct just before ejaculation.

III. CALENDAR METHOD

Is the method where by intercourse only takes place on days considered ‘safe’ within the menstrual cycle.

Calendar method is also called rhythm method

Advantages

> It is uncostly and it can be best practiced by married couples.

> It enables a woman to recorganize when she is fertile and when she is not.

Disadvantages

> It is very unreliable especially for women with irregular periods.

> It needs constant recording of the date the menstrual period starts, failure to do that may lead to conception.

IV. CERVICAL MUCUS (BILLING) METHOD

Is the natural method which involves the observation of the mucus in the vagina.

During fertile period the mucus gets thinner and becomes clear while during the infertile period, the mucus gets thicker and sticky.

Advantage

It is costless.

Disadvantages

It is not reliable as sperms can survive for 3 to 7 days and conception can thus occur.

It is not suitable for women with irregular cycles.

(b) ARTIFICIAL METHODS

Are those methods which involve the use of device or chemical substances Artificial methods include:

1. Condoms

2. Diaphragm

3. Implants

4. Contraceptive pills

5. Mini pills

6. Intra-uterine device (IUD)

7. Male sterilization

8. Female sterilization

1. CONDOMS (SHEATH)

Male condom is a thin rubber sheath worn by a man over an erect penis to collect sperms so that they are not released into the vagina

Female condom is a loose rubber fitting with two flexible plastic rings on either end

It is inserted into the vagina before intercourse.

Advantage

> It is simple to use

> It is 98% effective if used properly.

> It offers protection against sexually transmitted diseases

Disadvantages

> If not used properly it can tear, releasing semen into the vagina.

> Semen may also overflow leading to conception.

> Female condoms are expensive.

2. DIAPHRAGM

is a flexible dome shaped rubber fitted into the cervix

It is used with sperm killing chemicals (spermicides) preventing the sperm from fertilizing the egg.

It remains in the cervix for about six hours after intercourse to prevent conception.

Advantages

It is 92% effective if used properly.

Disadvantages

It may cause pain or abrasions during fitting.

It requires reapplication of jelly for each intercourse.

3. IMPLANTS

Are thin flexible tubes that contain progesterone which prevents ovulation.

The tubes are inserted under the skin on the underside of the upper arm and hormone is slowly released into the blood stream.

It also causes thickening of the mucus in the cervix thus preventing sperm from reaching the egg.

Advantages

Very effective (over 99%)

Fertility is restored immediately after removal of the implants.

Disadvantages

It requires specialized trained personnel to insert them.

They are expensive

Makea woman uncomfortable when they are touched.

4. CONTRACEPTIVE PILLS (COMBINED PILLS)

Are pills containing progesterone and oestrogen.

The pills are taken orally on daily basis to prevent ovulation.

Advantages

Easy to use, does not require regular check ups

Very effective when properly used ( over 99%)

Disadvantages

They may cause nausea, headache and weight gain

Failure to take the pills even for a day may lead to conception.

5. MINI PILLS

Are pills containing only progesterone which makes the lining of the uterus unfavourable for implantation of the fertilized egg.

Advantages

Very effective when properly used.

Disadvantages

They may cause weight gain and headaches

6. INTRA-UTERINE DEVICE

Is a small device made of plastic and copper that is inserted in the womb thus preventing the sperm from reaching the egg or the fertilized egg from reaching uterus for implantation.  It can stay in the womb between 3 to 10 years.

Advantages

Very effective (98 to 99%)

It is easy to fit

Disadvantages

Must be inserted and removed only by a trained professional

May cause heavy menstrual flow, back pain and PID

7. MALE STERILIZATION (VASECTOMY)

Is a minor operation that involves cutting off or blocking of the sperm ducts

Advantages

It is very effective (more than 99%)

Disadvantages

It is irreversible if it happens that a couple need to have a baby later.

The sperm ducts in some rare cases may rejoin thus causing conception and infection may occur.

8. FEMALE STERILIZATION

Is a minor operation in which the fallopian tubes are blocked or cut so that sperms never meet the egg.

Advantages

Very effective (99.5%)

Disadvantages

It is irreversible

IMPORTANCE OF MALE INVOLVEMENT IN FAMILY PLANNING

1. They can both agree on which method they find suitable.

2. Involving the male partner is also important when there are complications regarding the use of contraception.

3. To avoid misunderstanding and breakage of marriages.

SOCIAL-CULTURAL FACTORS AFFECTING FAMILY PLANNING AND CONTRACEPTION

The following are social-cultural factors affecting Family planning:

i. Customs and traditions

ii. Religious beliefs

iii. Economic status

iv. Maternal health

v. Education level

I. CUSTOMS AND TRADITIONS

In some societies a woman is not allowed to have sexual intercourse while breastfeeding. Therefore, a woman will abstain until she stops breastfeeding.

II. RELIGIOUS BELIEFS

Some religion such as a section of Christians and in Islam, the use of condoms is not advocated thus increasing the chances of conception.

III. ECONOMIC STATUS

People tend to be more conscious of having a large number of children for the fear of not being able to take care of them due to their economic status.

IV. MATERNAL HEALTH

A woman may be forced to become sterile due to health problems, for example a woman with ovarian cancer may be forced to undergo surgery to remove the uterus thus making her unable to have more children.

V. EDUCATION LEVEL

Couples who are more educated tend to be more conscious on the number of children to have than those who a less educated.

VI. MATERNAL AND CHIRD CARE

Are the special services provided to the mother and the baby in order to improve their well-being and prevent complications that may affect their health.

VII. ANTENATAL CARE

Are special services provided to the mother before the baby is born

Antenatal care involves health care.

The following are antenatal care provided to the mother before the baby is born:

i. A healthy diet

ii. Weight check-ups

iii. Blood group testing

iv. Rhesus factor testing

v. Amount of haemoglobin testing

vi. HIV, blood pressure and STIs check up

vii. Rest

viii. Exercise

ix. Love and support

x. Preparing the mother for delivery.

IMPORTANCE OF ANTENATAL CARE

i. It ensures the baby is developing well and if not, proper measures can be taken immediately to prevent any danger to the mother and the baby.

ii. Any signs of infections or abnormalities in the developing baby are detected and taken care of.

iii. It reduces complications during pregnancy such as ectopic pregnancy.

iv. It prevents mother to child transmission of diseases like HIV.

v. It enables the expectant mother to get nutritious food and food supplements such as acid for proper development of the baby.

NATAL CARE

Are special services provided to the mother during delivery in order to ensures safe delivery.

Example of natal care

> Being kind and gentle to her during delivery.

> Helping the expectant mother to give birth

> Relieving her pain through comforting or medication

Importance of natal care

> Ensures safe delivery

POST -NATAL CARE

Are special services provided to the mother and the baby after birth.

Post means after and natal means birth,

Example of post-natal care:

> A healthy diet

> Rest

> Exercise

> Immunization of the child

> Breastfeeding

> Love and support

> Good shelter

> Child health clinic visits

> Warmth

> Protection and hygiene

IMPORTANCE OF POST-NATAL CARE

1. To help the mother recover quickly

2. To maintain good health. Since a healthy mother produces enough milk to feed her baby so that it grows healthy.

NB: Mothers should breast-feed the child whenever possible

QUESTION: Why mother’s milk is better than any other food?

Answer: Mother’s milk is better than any food due to the following reasons:

i. It contains antibodies that are much needed to the child

ii. It contains much proteins and vitamins which are very important for the child’s growth

iii. Breast milk is easily digested than bottled milk. Therefore, children who take milk from their mother rarely suffer from constipation

iv. Breast milk is free from contamination

v. It contains some chemicals which help in development of the nervous system of the child

vi. Does not need any preparations

SOCIAL-CULTURAL FACTORS WHICH AFFECT MATERNAL AND CHILD CARE IN THE FAMILY AND COMMUNITY

The following are social-cultural factors which affect maternal and child care in the family and community:

i. Female genital mutilation

ii. Local belief

iii. Working

iv. Alcohol consumption during pregnancy

I. FEMALE GENITAL MUTILATION (FGM)

Is the practice of circumcising women.

The practice is said to have effects during childbirth. It causes women to experience pain, bleeding, and shock and may lead to infection.

II. LOCAL BELIEF

These are certain local beliefs and taboos such as banning women to eat certain types of foods such as protein rich foods, which could help to build their health and that of the child.

III. WORKING

Hard work such as cultivation may cause several problems to the pregnant woman such as miscarriage or pain.

VI. ALCOHOL CONSUMPTION DURING PREGNANCY

In most cultural practices taking alcohol is considered as a normal behavior. But alcohol during pregnancy affects both the health of the mother and that of the child.

APPROPRIATE WAYS OF PROVIDING MATERNAL AND CHILD CARE FOR PEOPLE LIVING WITH HIV/AIDS(PLWHA)

These following are appropriate ways of providing maternal and child care for People Living with HIV/AIDS:

1. To ensure frequent medical checkup and ARVs when necessary for both maternal and child.

2. To ensure they get well balanced diet

3. Avoid sharing sharp objects like razor blades

4. Counseling in order to help them deal with their feelings of loss and grief

5. To avoid discrimination for people living with HIV/AIDS

6. Ensure the use of polite language when providing care to them

7. Wearing of gloves when cleaning their bodies and clothes

REVISION QUESTIONS

1. Choose the correct answer

(i) The term parturition means:

A. Birth

B. Gestation

C. Implantation

D. Ovulation

A. One egg was fertilized and then divided into two

B. The uterus was large enough for two embryos to develop

C. Her ovaries produced two eggs, which were both fertilized

D. Twins were produced in her family history

A. Fertilization –implantation-ovulation

B. Ovulation – fertilization – implantation

C. Implantation – ovulation –fertilization

D. Fertilization – ovulation – implantation

A. Zygote     C. Foetus

B. Embryo     D. Young baby

A. Vagina     C. Oviduct

B. Uterus     D. Cervix

A. Bigamous     C. Bisexual

B. Hermaphrodite     D. Parthenogenic

A. Oxygen     C. Red blood cells

B. Antibodies     D. Water

V. In the figure below sperm are produced in: –

1. G     C. E
2. D     D. F

A. Seminal vesicle     C. Cowper’s gland

B. Prostate gland     D. Pituitary gland

A. D     C. B

B. C     D. A

A. D     C. F

B. E     D. G

A. H and G     C. H and D

B. A and G     D. A and D

B. Tying and cutting I

C. Collapsing B

D. Removing E

A. Uterus     C. Ovary

B. Vagina     D. Oviduct

A. Having of an egg fertilized by two sperms

B. Eggs fertilized by the same sperm

C. Having of a fertilized egg

D. Eggs released by the same ovary

B. Ova

C. Gametes

D. Zygotes

B. Oestrogen

C. Luteinizing hormone

D. Oxytocin

B. Embryo sac

C. Egg nucleus

D. Tube nucleus

B. Egg nucleus

C. Integuments

D. Pollen tube

B. Oxytocin

C. Vasopressin

D Oestrogen

XVI. Figure below is a diagram showing what happens during crossing over of homologous chromosomes. The part marked 1 is: –

A. Nucleus     C. Tetrad

B. Chiasma     D. Centromere

A. Nucleus     C. Tetrad

B. Chiasma     D. Centromere

A. 17^th     C. 21^st

B. 14^th     D. 28^th

XIX. The diagram below shows an intra- uterine device in position in a woman’s uterus. The part marked V is:

A. Egg     C. Uterus

B. Ovary     D. Vagina

A. Fallopian tube     C. Ovary

B. Egg     D. Uterus

A. G and O     C. S and G

B. E and S     D. A and S

A. Tube     C. Vagina

B. Uterus     D. Loop

A. Pollen attracts insects to the flower

B. Pollen grains are the male gametes

C. Pollen grains contain the male and female gametes

D. Pollen grains give a sweet smell to the flower

A. A zygote is produced by the fusion of male and female gametes

B. No new living organism can be produced without fertilization

C. A female gamete is bigger than a male gamete

D. A reproductive cell is a gamete

B. Scion and roots

C. Stock and a mature tree

D. Buds and leaves

A. Wild plant supplies the scion

B. Wild plant supplies the stock

C. Desired or required plant supplies the stock

D. Source of the stock or scion is not important

A. Testis, prostate gland, scrotum and prepuce

B. Seminal vesicles, testis, prostate gland and scrotum

C. Prostate gland, spermatic cord, testis and prepuce

D. Spermatic cord prostate gland and seminal vesicle

A. The release of an ovum from an ovary and the preparation of uterus to receive a fertilized egg to develop into a zygote are called fertilization.

B. The process of passing out dead unfertilized ovum and uterine lining in women is called menstruation

C. The embryo receives food from the placenta

D. After fertilization, the ovum dies and is released during menstruation.

(xxxiv) In which of following stages of meiosis do chromosomes appear as thin chromatin threads?

A. Interphase I

B. Interphase II

C. Anaphase I

D. Telophase II

(xxxv) Chromosomes become more visible during______

A. Telophase I

B. Interphase II

C. Prophase I

D. Anaphase

(xxxvi) At this stage of meiosis, new spindle fibres are formed at right angles to those formed during meiosis I.

A. Prophase I

B. Anaphase II

C. Anaphase I

D. Prophase II

(xxxvii) Crossing over occurs during______

A. Interphase I

B. Metaphase II

C. Prophase I

D. Anaphase II

1. Study the diagram below and answer the question that follow:

a. Name the parts labelled J, K, L, M, N and O (b) What does the diagram represent?

b. What is the origin of the endosperm tissue in seeds?

Structure K

Structure M

Structure O

2. The diagram below is of a human male urino-genital system. Study it and answer the questions that follow.

1. 

a. Name the parts labelled A, B, C, D, E, F, G, H, I, J and K

b. Which two of the above named parts are not parts of the reproductive system?

3. Vasectomy is a method of birth control involving an operation on part of the male reproductive system. Discuss

4. During circumcision which part is removed?

5. Between the fore skin and the glans of the penis accumulates a whitish substance known as———–

6. Where are the sperms made?

7. Where are the sperms stored?

8. The figure below shows a longitudinal section through a flower. Study the diagram and answer the questions that follow.

i. Name all the labelled parts A- I

ii. Which of the labelled parts of the constitute the gynoecium of the flower?

iii. The flower has both stamens and carpels. What term is used to describe such a flower?

iv. What do you understand by the term pollination?

v. The type of the ovary represented in the diagram is?

vi. Which part protects the flower in bud stages?

i. Spermatogenesis

ii. Oogenesis

(b) Where do spermatogenesis and oogenesis processes occur in the human body?

(c) What is the main difference between the two processes in (a) above?

i. Fertilization

ii. Implantation

iii. Gestation period

iv. Ovulation

v. Parturition

i. Development of female secondary sexual characteristics

ii. Preparation of the uterus for pregnancy

iii. Production and secretion of milk by mammary glands

iv. Contraction of uterus wall during birth

(ii) Luteinizing hormone

(iii) Androgen

(i) Placenta

(ii) Vas deferens

(iii) Epididymis

(iv) Prostate gland

14. What are advantages of internal fertilization over external fertilization?

16. What is the role of the fruit in the development of angiosperm seed??

17. With specific examples distinguish between oviparous and viviparous?

18. (a) Describe how fertilization occurs in a named flower?

(b) How are seeds formed?

(c) What are the differences between a seed and a fruit?

19. (a) What are the characteristics of an insect-pollinated flower?

(b) Define the term cross-pollination

(c) Mention three agents of pollination.

i. Androecium

ii. Gynoecium

iii. Corolla

21. Discuss how fruits/seeds are adapted for dispersal

(b) List the characteristics of wind pollinated flowers.

i. Name the disorder from which the baby was likely to have been suffering from.

ii. Explain how the disorder occurred.

iii. What measures could have been taken to save the baby?

24. The diagram below shows a female reproductive system.

(a) Name the parts labelled: A, B, C, D, E, F, G, H, I, J and K

(b) Where are sperms deposited?

(c) Where does fertilization normally occur?

(d) Which part releases the ovum?

(e) During birth control method i.e. tubal ligation, which part is tied and cut?

(f) Which parts are not associated with the reproductive system?

(g) Briefly explain the functions of the parts labelled C, D, E, F, G, H and I

25. The diagram below shows a foetus in the uterus.

i. Identify the parts labelled A, B, C, D, E, F, G, H and I

ii. Briefly explain the functions of the amniotic fluid during the development of the foetus.

iii. Which hormone is produced by the part I during the last six months of the pregnancy?

iv. What is the role of the hormone you mentioned in iii above?

i. Ectopic pregnancy

ii. Still birth

iii. Miscarriage

iv. Premature

v. Abortion

vi. Breech birth

(b) Give a brief account on the various sexual deviations in the society.

(b) Briefly mention five methods of family planning.

29. The diagram below shows an embryo and its placenta during the early stages of development.

1. 

i. Briefly list down the materials allowed to pass from the mother to the foetus.

ii. Briefly list down the materials not allowed to pass from the mother to the foetus.

iii. What materials does the foetus release to the mother’s blood?

30. (i) Which blood vessel (umbilical artery or umbilical vein) has greater concentration of amino acids?

(ii) Give reasons for your answer in (i) above.

31. Which blood vessel (umbilical artery or umbilical vein) has greater concentration of carbon dioxide?

32. Explain how oxygen in the maternal in the blood passes into the foetus blood supply.

34. Precisely describe which change occur in the circulatory system of the foetus soon after birth.

(b) Name five sexually transmitted diseases.

36. Outline ways of controlling and preventing the spread of HIV/AIDS

(b) Why happens to the ovum after fertilization takes place?

(c) Where does fertilization occur in mammals?

(d) What is the fate of the endometrium if fertilization does not occur?

(b) State ways in which the male gamete is adapted to movement towards the ovum.

39. (a) Name the accessory glands of the male reproduction system.

(b) What is the role of the glands in reproduction?

42. At which stage of life does the female reproduction cycle commence and does it end?

(ii) Name the episode that marks the start and end of each reproductive cycle.

(iii) What is the role of the umbilical cord during pregnancy?

44. (a) Name the organ through which substances are passed from the mother to the foetus.

(b) How is the organ named in (a) above adapted to its functions?

i. Testes

ii. Epididymis

iii. Vas deferens

46. State the effect of testosterone in reproduction.

47.  The diagram below shows a process in reproduction.

(a) (i) Name the process.

ii. Name the hormone that causes the process given in (i) (b) What is the role of the Graafian follicle?

48. The diagram below shows asexual reproduction in yeast cells.

(a) Name the type of reproduction shown in the diagram.

(b) Identify the structure labelled A

(c) State the biological importance of A.

49. (a) What type of reproduction does amoeba undergo?

(b) Explain how such type of reproduction takes place.