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2. CHAPTER -8 HOW DO ORGANISMS REPRODUCE?
Topics to be covered:
Introduction
What is reproduction?
Why is reproduction necessary?
Types of Reproduction
Asexual reproduction
-Fission
-Budding
-Regeneration
- Vegetative propagation
Sexual reproduction
- In plants
-In human beings
Reproductive health
Family planning

3. How do organisms reproduce?
Retain a particular species of living
organisms
Transmission of characters from one
generation to the next
Variations lead to the origin of new
species

4. Types of Reproduction:
Asexual Reproduction
-Single parent is needed to produce
the new organism
-No sex involved – primitive mode
- Daughter cells are identical
to the parent
Sexual Reproduction
-Involves two parents
-Fusion between male & female gametes
give rise to the new organism
-Sex is involved
-Daughter cells are different from parents

7. Asexual Reproduction:
Mode of reproduction in which new individuals are formed from a
single parent
New individuals are identical to the parent
Faster mode of reproduction
Types:
Fission
Budding
Regeneration
Fragmentation
Spore formation
Vegetative propagation

8. Fission:
An organism splits to form two or more new individuals
Types:
Binary fission
Multiple fission
Binary fission
-Two new individuals are
formed
-Nucleus divides only once
-Unicellular organisms like
amoeba, paramecium,
euglena, bacteria

9. Binary fission
•Leishmania is a protozoa
which causes kala-azar
•Whip like structure at one
end of the cell
•Longitudinal plane
Multiple fission:
Many new individuals are formed
Nucleus divides repeatedly
Takes place during
unfavourable conditions
(cyst formation takes place)
Amoeba, plasmodium, many algae

11. Fragmentation:
Parent breaks into multiple pieces on maturity, each of which give rise
to a new individual
Seen in simple multicellular organisms

12. Regeneration:
Parent if cut/ broken into multiple pieces, each gives rise to a new
individual
Accidental process
Hydra, flatworm, tapeworm

14. Spore formation:
Formation of new individuals by germination of spores
Spores:
Unicellular bodies in the parent that are capable of growing into a new
individual

15. Vegetative reproduction:
Mode of asexual reproduction in plants
Plant parts detached from the parent & form a new plant.
Natural Vegetative
reproduction
Root
Stem
Leaves
Artificial vegetative
propagation
Cutting
Layering
Grafting

16. Vegetative reproduction: By roots
Buds develop in thick, fleshy roots which later, when put into soil
develop into new plants
Sweet potato, dahlia, carrot
Sweet potato
Dahlia
Carrot

17. Vegetative reproduction: By stems
Runners:
Stems that grow horizontally above ground
Grass, strawberry

18. Underground stems: Potato
Vegetative propagation in potato takes place by stem.
From the activity of growing potato by vegetative propagation it can be
found that, new plants grow from the buds within few days.
If such a potato is placed in soil, it has the capability to form a complete
plant.

19. Underground stems: Onion
Vegetative propagation in onion takes place by stem.
From the activity of growing onion by vegetative propagation it can
be found that, onion bulbs have thick, short stem in the form of
condensed disc.
The disc bears terminal and axillary buds.
The axillary buds grow into new green aerial shoots.

20. Vegetative reproduction: By leaves
Buds are formed along leaf margins which later give rise to a new
plant
Example: Bryophyllum ( Miracle leaf plant, sprout leaf plant)

21. Artificial Vegetative reproduction:
Cutting:
A plant part is cut from the parent & put into
the soil which later give rise to a new plant.
Stem cutting: Rose, sugarcane
Root cutting: Dahlia
Layering:
New plants are formed from stems of parent plant without detaching
them initially from the parent.
A variety of plants can be grown by this method like strawberry, guava,
lemon, china rose etc..

22. Grafting
Stems cut from two different plants are attached to grow as a
single plant.
This improves the quality of certain plants.

25.  Male reproductivepart consist of
anther and filament
Anther produces pollen grains
which contains
the male germ cell (male gamete)

26. Pistil is the female
reproductive part. It produces
ovules in the ovary which
contain the female germ cell
(female gamete)

27. The transfer of pollen grains from the anther to the stigma
of a flower is called pollination. It takes place by wind,
water or insects. If the pollen grains are transferred from
the anther to the stigma of the same flower it is self
pollination and if it is transferred from the anther of one
flower to the stigma of another flower it is cross
pollination.
AGENTS OF POLLINATION-Pollination takes place
by insects, wind, water etc.

28. After the pollen grain is transferred to the
stigma it produces a pollen tube which
passes through the style and enters the ovary
and ovule. In the ovule the male germ cell
(male gamete) fuses with the female germ cell
(female gamete) to form a zygote. This
process is called fertilisation.

29. After fertilisation,

32. The male reproductive system consists of a pair of
testes which produces the male reproductive cells
called sperms and the hormone testosterone.
It is contained in sac like structures called
Scrotum-located in outside- It maintains low
temperature for the production of sperms.
From each testis arises a tube called
vas deferens- acts as passage where sperms reach up to
urethra
.
The urethra is enclosed in a muscular organ called
penis. It has an opening called genital pore.
The seminal vesicles and prostate glands produce
fluids which provide nutrition and help in the
movement of the sperms.

33. Female reproductive system :-
1. The female reproductive system
consists of a pair of ovaries which
produces the female reproductive cells
called ova or eggs and the hormone
oestrogen.
2. Above the ovaries are tubes called
oviducts or fallopian tubes.
3. The two oviducts unite into a bag like
structure called uterus.
4. The uterus has opening called vagina.
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