TOPIC 3: REPRODUCTION (II) ~ BIOLOGY FORM 6
2) Copulation
3) Fertilization
4) Cleavage
5) Implantation
6) Pregnancy
7) Parturition(birth)
8) Parental case.
sperm passes as a long tail coupled to a head which contain a haploid nucleus.
chromosomes.
chromosomes.
the non – motile spermatid into motile spermatozoa.
involved in the synthesis of testosterone from cholesterol.
STRUCTURE OF MATURE HUMAN SPERMATOZOANS
Structure of mature human sperm
coelom epithelium.
Fig: The egg cell
1)Cleavage
2)Blastulation
3)Gastrulating
4)Neurilation
5)Organogenesis
CLEAVAGE
i) Chorion
ii) Amnion.
iii) Allantos.
iv) York sac.
i) Progesterone.
ii) Oestrogen.
iii) Human chorionic gonadotrophic hormone.
eggs, fish, beef etc. for proper growth and development.
2. Social interaction/Education
to live actively in the social unit.
structures of the coelomate epithelium into the stroma of the primary bipotent gonalds as oogonia during embryonic development.
release oocytes (ovulation).
hypothalamus, pituitary and ovary are there by in dynamic interaction.
1.FOLLICULAR PHASE
This is characterised by:-
3.LUTEAL PHASE
early in mammals, where all of the meiotic and differentiation into oocytes before or just after birth, but ovulation does not take place until much later.
Fig: Uterine cycle
Fig: life cycle of a grasshopper
(i) Microsporogenesis.
(ii)megasporogenesis.
MICROSPOROGENESIS
DOUBLE FERTILIZATION AND ITS CONSEQUENCES
Double fertilization is a unique characteristic of the angiosperm. It is a result of multinucleate of the pollen grain and embryo sac.
Definition: Double fertilization is a type of fertilization which occurs in the flowering plant where the two types of nuclear fusion take place.
First: The male gamete nucleus fuses with the female gametes of the embryo sac to form the zygote (2n).
Second: The second male gamete fuses with diploid nucleus (resulting from the fusion of 2 polar nuclei) forming a primary endosperm (3n).
MECHANISM OF DOUBLE FERTILIZATION
The process of double fertilization is proceeded by pollination during which the pollen grain lands on the stigma.
As the pollen grain lands on the stigma the style tissue stars to secrete sugary solution including sucrose solution. The solutions are absorbed by the pollen grain which consequently swells.
As a result of swelling; the intine wall grows through the exile via one of the pits as pollen tube under the control of pollen tube down the style.
As the pollen tube continues to grow, the generative nucleus in the pollen grain divides by mitosis to produce two male gametes. In embryo sac, the two pollen nuclei fuse producing a diploid nucleus and the antipodal as the sinergid degenerate.
The embryo sac thus remains with only two nuclei an ovum (n) and a diploid nucleus resulting from the fusion of the polar nuclei.
The pollen tube continues to grow chemotactically towards the embryo sac under influence of chemicals secreted by the embryo sac. As the pollen tube reaches the micropyle, the following occurs in the pollen tube:-
The tip of the pollen tube bursts.
The contents of the pollen grain are discharged into the vicinity of the embryo sac.
Fertilization occurs following the discharge of contents of pollen grains. It is a double fertilization
How?
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