hj

2. SEXUAL REPRODUCTION
• Sexual reproduction involves formation of
the
male and female gametes, either by the same
individual or by different individuals of
the
opposite sex.
These gametes fuse to form the zygote
which
develops to form the new
organism.

3. JUVENILE PHASE/ VEGETATIVE
PHASE
• All organisms have to reach a certain stage of
growth and maturity in their life, before
they
can reproduce sexually.
• That period of growth is called the juvenile
phase.

4. . .
EFE.T
:LTS:IIJ
LEIU•·•-
:,R:EJ!TOD1
OQTON:
;,
Sexual
reproduction J
events
Pre-fertilisation
Syngamy and
fertilisation
Post-fertBisation
Gametogenesis Gamete transfer

5. 1 PRE-FERTILISATION
EVENTS
1. GAMETOGENESIS
2. GAMETE TRANSFER

6. GAMETOGENESIS
• If the parent body is haploid gametes are
formed by mitosis, if diploid gametes are
formed by meiosis.
• An organism may be homothallic/monoecious
or heterothallic/dioecious

8. GAMETE TRANSFER
• In some organisms both gametes are motile
(algae) but in most cases male gamete is motile
where as female is not.
• Algae, bryophytes and pteredophytes, water is
the medium for gamete
transfer
Pollination is the method of gamete transfer in
higher plants as pollen grains contain male
gametes.

10. TYPE OF FERTILISATION
• External fertilisation
Ex. bony fishes and frogs
• internal fertilisation
Ex. Higher plants

11. POST-FERTILISATION
EVENTS
The events after zygote formation is called
post-fertilisation events.
Zygote development
(i) type of life cycle of organism
and
(ii) the environment it is exposed
to.
In algae and fungi it develops a thick wall around it
to resist desiccations and damage and undergoes a
period of rest.

13. POST-FERTILISATION
EVENTS
 In oviparous animals zygote development occurs outside of
female's body, they are egg laying e.g. reptiles, birds.
• In viviparous animals zygote development
occurs inside of female's body. They give birth to
young individuals. E.g. mammals

15. OVIPAROUS VIVIPAROU
S
Animals lay fertilise or
unfertilised eggs.
Eggs have shell
Give birth to young
individuals.
No shell

16. NOT
OVIPARO
US

17. SEXUAL
REPRODUCT
ION
 Savesenergy
 Courtshipisa non-issue
 Greatest increaseinfitness for eachindividual
 low GeneticVariability
 Adaptationto environmentis difficult
 "Retards" evolution
Asexual
Reproduction
• HighGeneticVariability
Advantage
s
• Facilitatesadaptatlon
• "Speeds" upevolution
• EnergyCostly
Disadvantage
s
• Courtshipistime/resource
consuming
• Usuallysacrificesthe fitness of
one sex to the other.