The various methods of reproduction employed by different organisms are discussed here which include Asexual & Sexual reproduction along with Vegetative methods employed by Plants for their propagation

1. UNIT VI-
REPRODUCTION
CHAPTER-1 REPRODUCTION IN ORGANISMS

2. INTRODUCTION

3. LIFE SPAN
Each and every organism can live only for a certain
period of time.
The period from birth to the natural death of an
organism represents its life span.

4. LIFE SPAN COMPARISONS

5. SEQUOIA TREE

6. PHASES OF LIFE

7. REPRODUCTION

8. REPRODUCTION
• Reproduction is defined as a biological process in which an
organism gives rise to young ones (offspring) similar to itself.
• The offspring grow, mature and in turn produce new offspring. Thus, there is a
cycle of birth, growth and death.
• Reproduction enables the continuity of the species, generation after generation.

9. TYPES OF REPRODUCTION
REPRODUCTION
ASEXUAL SEXUAL

10. ASEXUAL REPRODUCTION

11. ASEXUAL REPRODUCTION
• When the offspring is produced by single parents with or without the involvement of
gamete formation, the reproduction is called asexual reproduction.
1. Usually followed by organisms with relatively simpler organizations.
2. Off springs produced by single parent.
3. With/without involvement of gamete formation.
4. Off springs produced are genetically and morphologically similar to each other and to
the parent, i.e. they are clones.

12. TYPES OF ASEXUAL REPRODUCTION

13. ASEXUAL REPRODUCTION
BUDDING IN HYDRA
BUD CONIDIA IN PENICILLIUM
ZOOSPORES IN
CHLAMYDOMONAS

14. ASEXUAL REPRODUCTION (VEGETATIVE PROPAGATION)
LEAF BUD-BRYOPHYLLUM

15. SEXUAL REPRODUCTION

16. SEXUAL REPRODUCTION
• When two parents (opposite sex) participates in reproduction process and also involves
the fusion of male and female gametes, it is called sexual reproduction.
• Involves formation of male and female gamete by two individuals of the opposite sex.
• Offspring produced by fusion of male and female gametes not identical to each other or
to the parents.
• All sexually reproducing organisms share a similar pattern of reproduction.
• In sexual reproduction, fusion of male and female gametes results in offspring that are
not identical to parents.

17. PHASES IN SEXUAL REPRODUCTION
1. Juvenile phase –
The period between birth and sexual maturity is called juvenile phase. In plants it is known
as vegetative phase.
The end of juvenile/vegetative phase marks the beginning of the reproductive phase.
2. Reproductive phase-
• Some plants show flowering in particular season and some other flowers in all seasons.
• The female placental animals exhibit cyclic change in activities ovaries and accessary
glands as well as hormone during the reproductive phase.
3. Senescent phase -
It is the end of reproductive phase. Old age ultimately leads to death

18. EVENTS IN SEXUAL REPRODUCTION
• Events in Sexual Reproduction
● Organisms reproducing sexually exhibit certain events.
These are:
○ Pre-fertilisation events
○ Fertilisation events
○ Post-fertilisation events

19. EVENTS IN SEXUAL REPRODUCTION
PRE-FERTILISATION EVENTS

20. PRE-FERTILISATION EVENTS
● Events taking place before the fusion of the gametes
consist of:
○ Gametogenesis ○ Gamete transfer
1. Gametogenesis
● Process of formation of gametes (male and female)
● Gametes are haploid
● In some organisms (like algae), they are almost
similar (homo or isogametes).
● In others, the two gametes are morphologically and
physiologically different (heterogametes), and are of
two types
- antherozoid or sperm (male gamete) and
- egg or ovum (female gamete).

21. PRE-FERTILISATION EVENTS
- In some organisms both the sexes are present in the same individual
(monoecious or homothallic), if present in two individuals (dioecious or
heterothallic).
- In a unisexual flower, the male flower is called staminate and the female
flower is called pistillate.
- Gamete formation takes place by cell division.
- In haploid parents, it is by mitosis; in diploid parents, it is by meiosis, with
specialised cells called meiocytes undergoing meiosis.

22. DIVERSITY OF SEXUALITY IN ORGANISMS
Homothallic
(Monoecious)
Hermaphrodite
Ex :- Earthworm
Heterothallic
(Dioecious).
Ex:- Cockroach
Bisexual.
Unisexual
Ex:- Marchantia

23. PRE-FERTILISATION EVENTS
2. Gamete Transfer
● For their fusion to take place, the gametes need to be transferred.
● In most organisms, the male gametes are motile, while the female gametes are non-
motile, and the male gametes need a medium for their movement.
● In angiosperms, the pollen grain carries the male gamete and the ovule carries the
female gamete.
● Pollen grains are produced in the anther and need to be transferred to the stigma for
fertilisation to occur.
(This is easy in monoecious plants as both the anther and the stigma are present close
by; in dioecious plants, it takes place by pollination).

24. POLLINATION
• Pollination is a method where pollen grains are picked from an anther, which is
the male part of a flower and transferred to the flower’s female part called the
stigma.
• Pollen grain germinates on the stigma.
Germinating
pollen grains on
stigma

25. POLLEN TUBE FORMATION
POLLINATION
POLLEN TUBE FORMATION
FUSION OF THE MALE AND FEMALE GAMETE
FERTILISATION (SYNGAMY)
SCHEMATICS.

26. EVENTS IN SEXUAL REPRODUCTION
FERTILISATION

27. FERTILISATION
• Fertilisation – The fusion of male and female gamete is called fertilisation or
syngamy. It results in the formation of diploid zygote.
• Based on its occurrence there are two different types of Fertilisation
EXTERNAL FERTILISATION INTERNAL FERTILISATION
Syngamy occurs outside the body of
the organism.
Syngamy occurs inside the body of the
organism.
Large number of gametes are released in
the surrounding medium.
Number of ova produced are less, but
large number of male gametes are
released
Ex:- Bony fishes, Amphibians Ex :- Birds, Mammals
• The process of development of new organisms without fertilisation of female gametes is called
parthenogenesis. Ex:- honey bee, rotifers, and lizards

28. EVENTS IN SEXUAL REPRODUCTION
POST-FERTILISATION EVENTS

29. POST-FERTILISATION EVENTS
• Post Fertilisation Events- events in the sexual reproduction after formation of
zygote.
• Every sexually reproducing organism, including human beings begin life as a single
cell–the zygote.
• In the organisms, having external fertilisation,
• zygote is formed in external medium (water) and
• those having internal fertilisation zygote is formed inside the body of female.
• In algae and fungi, zygote develops a thick wall resistant to desiccation and damage.
This germinates after a period of rest.

30. POST-FERTILISATION EVENTS
• Embryogenesis – the process of development of embryo from the zygote.
• During this, zygote undergoes mitotic division and cell differentiation.
• Cell division increase the number and cell differentiation help in formation
of new group of cells and organs.
OVIPAROUS VIVIPAROUS
Development of zygote takes place
outside the body of the organism.
Development of zygote takes place
inside the body of the organism.
Organisms lay fertilized or
unfertilized egg.
Organisms produce young ones.
Ex:- Reptiles, Birds Ex :- Humans, Dog, Horse (Mammals)

31. POST-FERTILISATION EVENTS
• In flowering plants, zygote is formed inside the ovule. After fertilisation, sepals,
petals and stamens of flower fall off.
• The zygote develops into embryo and ovules into seeds.
• The ovary develops into fruits which develop a thick wall called pericarp,
protective in function.
• After dispersal, seeds germinate under favorable condition to produce new plants.
Different kinds of fruit showing
seeds (s) and pericarp (p)

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