Reproduction in organisms

REPRODUCTION IN ORGANISMS
CLASS XII
UNIT- 1
Chapter-1
PRESENTATION BY –
ANITA MISHRA
BIRLA BALIKA VIDYAPEETH, PILANI
RAJASTHAN

LIFE SPAN
Any organism survives for a particular period of time, which is the duration
between birth to death of the organism. This span is termed as life span.
• The Life span is a variable
attribute of an organism it may
be very short or prolonged.
• The life span has following
stages:
Birth------ Juvenile/Vegetative
phase------ Reproductive
phase-------Senescence/Aging
-------Death
S. No. Organism Life span
1 Elephant 60- 90 years
2 Rose 5-7 years
3 Dog 20-30 years
4 Butterfly 1-2 years
5 Crow 15 years
6 Banana 25 years
7 Cow 20-25 years
8 Parrot 140 years
9 Crocodile 60 years
10 Horse 60 years
11 Drosophila 30 days
12 Rice plant 3-4 months
13 Tortoise 100-150 years
14 Banyan Tree 200 years

REPRODUCTION
It is a biological phenomenon by which an organism gives rise to young
ones of its own kind
DIVERSITY
IN
THE MODES
OF
REPRODUCTION

REPRODUCTION
Reproduction ensures continuity of species generation to generation.
There is a diversity in modes of Reproduction in organisms:

ASEXUAL REPRODUCTION
It is a type of reproduction wherein the offspring do not come not from the union of gametes but
from a single parent hence the offspring are clones( genetically identical to the parent).
Binary fission
• In the unicellular organisms like Amoeba cell division only is the mode of reproduction.
• Mother cell withdraws pseudopodia & its nuclei elongates & gradually it divides into two by mitotic
karyokinesis.
• Finally the cytokinesis occurs by constriction or furrow formation between the two daughter nuclei.
• Amoeba like organisms are immortal as they exhibit a mode of asexual reproduction where the
parent body divides & distributes its protoplasm into two young ones, which continue to divide
hence forth & make the organism seemingly immortal ( Although the identity of the parent is lost).

Multiple fission
• Asexual reproduction in unicellular organisms,
like sporozoan Protozoans, is a type of fission in
which the nucleus divides a number of times,
followed by division of the cytoplasm, to form
daughter cells.
• Asexual reproduction of Plasmodium occurs in
human RBC.
• Multiple fission is a mode of survival of
organism through unfavorable conditions.
• To survive through adverse conditions the
daughter cells develop additional cyst wall.

Budding ( Outgrowth formation)
Budding is of 2 kinds
Exogenous Budding-
Budding in Yeast-
a) In the unicellular organisms like Yeast or
saccharomyces cerevisiae an outgrowth called bud
develops & pinches out in form of bud.
b) The buds keep on getting added pushing the first
formed bud outside & the last towards the mothers body.
Budding in Hydra-
a) An tiny outgrowth is formed which grows with time.
When fully developed the bud detaches & develops into
new hydrae.

DIFFERENCES BETWEEN ASEXUAL REPRODUCTION MODES

Budding
Budding is of 2 kinds
Endogenous Budding-
Budding/ Gemmule formation in Sponges-
a) Gemmules are internal/ endogenous buds of sponges
formed asexually.
b)It has a mass of totipotent cells called archaeocytes which
is capable of growing into new organism.
c) A gemmule has Spicules for skeletal support & a
micropyle for release of archaeocytes.

Spore Formation/ Sporulation
Endogenous Sporulation:-
• Spore formation is a method in which
Spores unicellular reproductive bodies are
formed in sacs called sporangia.
• When spores mature sporangia burst and
spores are carried to different location by
air, wind, water.
• When spores fall on a suitable ground,
they germinate and develop new
individuals.
for eg: Rhizopus/ Bread mould

Endogenous Sporulation:-
• Spore formation is a method in which
Spores unicellular reproductive bodies are
formed in the body of unicellular
organisms.
• Flagellated spores called zoospores are
formed in unicellular algae like
Chlamydomonas.
• During favorable conditions the mother
cell gets ruptured to release & disperse the
zoospores for multiplication.

Exogenous Sporulation:-
The asexual spores borne externally on the
cell which produces it is called exogenous
spores.
Conidia are asexually produced spores
that are borne externally to the
cells/Conidiophores that produce them in
Penicillium notatum.

Fragmentation in Spirogyra
• Fragmentation is a type of asexual reproduction
in which an organism simply breaks in
individual pieces at maturity.
• These individual small pieces then grow to form
a new organism e.g., algae Spirogyra.
• Spirogyra undergoes fragmentation which
results in many filaments.

Fragmentation in Planaria
• Fragmentation in flat worm is slightly
different- as in this mode of asexual
reproduction the broken pieces of body,
regrow their broken parts unlike
fragmentation where the broken pieces
immediately after been broken act as
individual organisms.
• For eg; Planaria

Vegetative Reproduction in Plants
• The Asexual
reproduction
in higher
plants where a
new plant
grows from the
vegetative
parts of plant –
root, stem, leaf
instead of
flower.

Natural Vegetative Propagation-
By Roots- In sweet potato & Dahlia the
underground roots grow
adventitious buds to form new
plants. For eg: Dahlia, Sweet potato

By Underground Stems
Rhizome- The irregular underground stem
grows horizontally with adventitious buds to
reproduce. For eg: Ginger, turmeric, banana.
Tuber- Adventitious buds found in
depressions on the underground stem called
tuber- the eyes are capable of growing into
new plant. For eg: Potato

By Underground Stems
Bulb- The disc shaped underground stem which
bears central bud surrounded by fleshy & scaly
leaves grow into new plants For eg: Onion,
Garlic
Corm- Adventitious buds found in on the
underground vertically growing stems called
corm can grow into new plant. For eg: Colacasia.
Alocasia, Gladiolus

By Sub- Aerial Stems
Runner- A runner is the stem portion of the plant that
which grows horizontally on the surface of ground.
The nodes of the runner produce adventitious buds that
develop into new plants that are clones. For eg: Cynodon
dactylon (Doob grass) Oxalis
Stolon- Stolons are weak horizontal above-ground stems
that are used by many plants as a means of asexual
reproduction.
The plants send out a stolon on the surface of the soil and
grow a adventitious bud on the end of stolon.Stolon of strawberry

By Sub aerial Stems
Offset- Offset is part of branch or stem which bears
rosette of leaves & cluster of roots at nodes.
The adventitious buds on nodes of offset can
grow into plants which are clones of mother plant.
For eg.: Eicchornia crassipiens, Terror of Bengal
Water Hyacinth
Sucker- Adventitious buds found in on the
underground root grows stem called sucker which
arches out of ground & strikes out aerial stem. For
eg: Chrysanthemum.

By Leaf
Species in the genus Kalanchoë (Crassulaceae)
reproduce asexually by forming plantlets
along their leaf margins.
All Bryophyllums belonging to this genus
grow adventitious roots in the notches of the
leaf.
Each bud can grow into new plant.

SEXUAL REPRODUCTION
means the reproduction involves the coming together of genetic material from two
parents so as to produce an offspring. Two haploid gametes unite resulting in a
genetically distinct diploid offspring.

Reproduction in organisms

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