TOPIC 4: EVOLUTION | BIOLOGY FORM 4
The universe is a system made up of the stars, planets and the space surrounding them. The earth is the one of the planets in the universe.
Plants, animals and other organisms like man, inhabit the earth. For
many centuries man has witnessed and appreciated changes, which occur in
nature and within his immediate surroundings. For example manythousands of years ago the Sahara desert was not there, instead the
entire area was covered with a thick forest. Due to changes in weather
the forest gradually disappeared and gave way to present desert. All
this gives us the concept about organic evolution.
Evolution
is the gradual development of organisms from simple form to more
complex forms over a long duration of time. Evolution is marked by
emergence of new species from pre-existing species and the disappearance
of some species. The species that disappear are said to become extinct.
- Carbon dating: This is a method of estimating the ages of dead materials of biological origin.
- Natural Selection:
This is selective force occurring in nature, which is responsible for
eliminating the unfavourable traits to retain only favourable traits in
the population. - Specie: These are organisms, which have ability to interbreed freely to produce fertile off springs.
- Fossils: These are the remains of organisms that lived in the past, preserved naturally in rocks, peat or ice.
- It
helps to understand the biological forces that cause organisms to
develop from simple to more complex organisms to the extent of new
species emerging - It helps to know how different organisms relate
The basic ideas about the origin of life
Outline the basic ideas about the origin of life
origin and diversity of life is based on the contribution of
theologists, philosophers and scientists. Early scientists put forward
theories, which suggested that life originated from non-living matter.
However changes in climatic conditions, habitats and complexity of
living organisms contradicts these suggestions.
Modern
scientists put both theories, which suggest that the origin and
diversity of life was brought about by the process of evolution. Two of
the most well known of evolution scientists are:
- Jean Baptiste Lamarck
- Sir Charles Darwin
are numerous theories of evolution that try to explain the origin of
living things. The main theories of the origin of life are:
- Theory of Special Creation
- Theory of Chemical Evolution
- Theory of Spontaneous Generation
- Steady State Theory
According
to this theory life was non-existent before a particular time. Then the
Supreme Being (Supernatural power) created all living things and there
was life on Earth from then henceforth.
theory proposes that differences and similarities between organisms are
as a result of how the organisms were created. Major religions like
Christianity, Islam and Buddhism have theories that support special
creation. The theory of fixed status and catastrophism was put forth by
Cuvier to support the religious point of view. According to Curvier,
fossils were brought about by catastrophes such as floods as outlined in
the holy bible. During the floods the earth’s surface was deformed and
many creatures were killed and covered by a mass of land.
to this theory, about 13.7 billion years ago, a cosmic explosion
occurred and the universe has since been expanding and cooling. Before
the explosion, the earth was very compact, dense and hot.
formation of the universe created condition like high ultraviolet
radiation and high temperatures. The gaseous composition was different
from todays. The universe cooled and protons combined with electrons to
form hydrogen atoms, which were the first atoms to be formed.
combined chemically with other elements to form compounds such as
water, hydrogen is present in almost all organic compounds.
theory was advanced by Alexander Oparin in 1923, he stated that in the
beginning the atmosphere contained ammonia, carbon dioxide, helium,
hydrogen and methane but lacked oxygen. The compound was a result of
high temperature, ultraviolet radiation and electrical discharge that
were plentiful after cosmic explosion.
compounds were dissolving in rainwater to form nutrient both (a mixture
of organic compound in water that accumulated in the water bodies on
the earth’s surface). The simple compounds combined to form complex
substances, using energy from the high temperature and ultraviolet rays
later polymers such as proteins lipids and carbohydrates were formed.
The first single-celled organism arose from these polymers.
formation of ribonucleic acid (RNA) a self-replicating molecule was a
pre-requisite to life as the form could replicate itself. Living
organisms could reproduce themselves. The first life forms were
heterotrophic using the compound in the nutrient broth as food. The
organisms reproduced by budding
Century but it is no longer applied. The scientists believed that
simple organisms like worms and frogs could arise from mud, dust or
rotten food. That means life can originate from non-living matter e.g.
maggots can arise from rotten meat.
theory was popular during the 1950s and 1960s, before its demise in the
late 1960s. According to these theory the universe has always existed
and has no origin that is it did not have a moment of creation this life
has no origin
Also
this theory states that or suggests that life on earth originated from
elsewhere. In eighteenth century scientists questioned these steady
state and Cosmozoan theories due to the presence of fossils and
emergence of new species.
Lamarck’s theory of Evolution
was not the only person to develop a theory of evolution. Jean-Baptiste
Lamarck was a French scientist who developed an alternative theory at
the beginning of the 19th century. His theory centred on two ideas:
- the law of use and disuse
- the law of inheritance of acquired characteristics
His
theory stipulated that a characteristic which is used more and more by
an organism becomes bigger and stronger. One that is not used disappears
eventually. Any characteristic of an organism that is improved through
use is passed to its offspring.
Baptiste Lamarck was a French naturalist. Lamarck formulated a theory
on evolution after studying botany and the fossils of marine
invertebrates.
used the law of use and disuse which explains that organism enhanced
certain abilities by exercising them and lost other abilities through
disuse example the ancestors of the present day long necked giraffe.
These early giraffes fed on short plants when the short plants became
scarce the giraffe had to stretch their necks to feed on taller plants.
Thus their necks became longer. The longer necks were passed onto their
offspring hence after a long time giraffe developed the long necks they
have today.
theory was based on inheritance of acquired characteristics the
offspring then adapt further, advancing evolution of the species.
Merits and Demerits of Lamarck’s Theory of Evolution
Outline merits and demerits of lamarck’s theory of evolution
- Lamarck theory lead to further studies on evolution of species
- It gave rise to discovery of genes and genetics which is now widely used in many fields of biology
- Upon
rejection of his theory Lamarck decided to study about invertebrates
which made great contribution in development of Zoology
Robert Darwin (1809 – 1882) was an English naturalist. He based his
theory on observation made during a five-year geographical study.
- Every
generation of organisms have more off springs than parents. However,
the number of adult organisms remains generally stable from generation
to generation. Therefore is a struggle for existence that causes many
off spring to die before becoming adults - There are many
variations in a species. Variations are passed from parents to their off
spring. Advantageous variations enable survival in the environment
organism with disadvantageous variation due. This is called survival of
the fittest. - Off springs with favourable variations grow into
adults and reproduce therefore favourable variations accumulated in the
species; enabling adaptation to the environment, this gives rise to new
specie. - A change in the environmental conditions favours other
characteristics of the organisms. The effect of these changes on the
organisms is that other features become more prominent than before
resulting in evolution.
- The theory enabled scientists to carry further studies, leading to new discoveries that suggest the origin of life
- Helped scientists to understand about drug resistance and evolution of germs like bacteria and viruses leading to new strains
- Enable further research to find cure or vaccines of germs, bacteria and viruses
Shortcoming
of Darwin’s Theory:He failed to explain how variations in populations
arose and were maintained from one generation to the next.
Evidences and application of Organic Evolution in the Real Life Situation
Some of these methods are
Comparative anatomy:Comparative
anatomy is the study of biological structures in different organisms.
The scientists look at structures that are similar in different
organisms or species. Example limbs of vertebrates such as human beings,
goats and wings of birds are used for different purposes but they have a
basic design structure, this is known as homologous structure.Example
fore limbs of humans are for manipulation, fore limbs of birds (wings)
are for flight and fore limbs of a goat are for walking; this shows that
all these animals are from common ancestors. Analogous structures are
the ones, which look different, but they perform similar functions e.g.
insect, birds and bats all have wings used for flight but they have
different structural organization.
Fossil records:Fossils
are remains of organisms that lived in the past preserved naturally in
rocks or on ice. The study of fossils is known as paleontology when
fossils are dated scientists can estimate the age of that organism.
Method used by scientists to know the age of fossils is carbon dating
using isotope of Carbon 14.
Embryology:In
comparative embryology embryos of different vertebrates at early stages
are compared and they are seen to have resemblances. Species that show
similar embryonic development are assumed to be closely related although
the adult may be quite different
Natural Selection in Action:Nature
led to the selection of a genetic combination that resulted in a more
frequent melanic variety compared to the non-melanic variety. Before the
industrial revolution in Europe the white variety of moth was more
prevalent. Industrialization in Europe in the 18th Century
polluted the environment, burning of coal released a lot of soot and
smoke. These pollutants coated tree trunks, killing the lichens that
grew on the tree trunks. The colour of the tree trunks became black;
this camouflaged the dark melanin form of the peppered moth. The
predators of the moth did not feed on many dark moths because they were
not very visible.
Evidence from vestigial organs:These
are structures, which have been greatly reduced and ceased to be
functional. Presence of vestigial organs is an indication that they
existed in ancestral forms but as a result of evolution such structures
have been so much reduced to the extent of loosing or greatly changing
their original function. Examples of vestigial structures are wings of
flightless birds such as ostriches and penguins.
Recommended:
- TOPIC 1: GROWTH | BIOLOGY FORM 4
- TOPIC 2: GENETICS | BIOLOGY FORM 4
- TOPIC 3: CLASSIFICATION OF LIVING THINGS | BIOLOGY FORM 4
- TOPIC 5: HUMAN IMMUNO DEFICIENCY (HIV) ACQUIRED IMMUNO DEFICIENCY SYNDROME (AIDS), AND SEXUAL TRANSMITTED INFECTIONS (STI’s) | BIOLOGY FORM 4
- TOPIC 3: BALANCE OF NATURE | BIOLOGY FORM 2
- TOPIC 4: TRANSPORTATION OF MINERALS OF LIVING THINGS | BIOLOGY FORM 2
- TOPIC 5: GASEOUS EXCHANGE AND RESPIRATION | BIOLOGY FORM 2
