Class12 reproduction in organisms CBSE

REPRODUCTION IN
ORGANISM
Shivani Khare
CBSE/chapter1
Khare.forensics@gmail.com/CBSE/XII 4/7/2016 1

 Need for Reproduction
 Modes of reproduction
 Types of asexual reproduction
 Events of sexual reproduction
 Special Modes of Reproduction

• Reproduction is a biological process in
which organisms produce offspring similar
to themselves. The offspring grow and
mature to repeat the process.
• The period from birth to the natural death
of an organism represents its life span.
Stages of Life Span Feature
Juvenility Organism develops the capacity to reproduce.
Maturity Reproductive phase begins.
Ageing and
Senescence
It is progressive deterioration in the body of the
organisms.
Death Permanent stoppage of vital functions.

ORGANISMS LIFE SPAN
May fly 1 day
Butter fly 1-2 weeks
crow 15 years
crocodile 60 years
man 100years
parrot 140 years
tortoise 100-150 years
Wheat plant 6 months
Rose 10 – 15 months
Dog 17 years
Elephant 70 years
Banana 2 – 3 years
Cow 22 years
Fruit Fly 1 month
Rice plant 4 months
Banyan tree 200 years
Life spans are
not necessarily
correlated with
their sizes.

• Continuity of species
• Population organization [young, adult and aged]
• Variations [Survival advantage]
• Existence of Life

 Asexual : Production of offspring by a single
parent with / without involvement of gamete
fusion.
 Sexual : Process of development of new
individuals through formation and fusion of
gametes.

CBSE/2013/SKH
ASEXUAL SEXUAL
A single parent is involved. Two parents (a male and a
female)
No formation or fusion of
gametes
Formation and fusion of
gametes
Involves mitotic division Involves meiosis
Individuals are genetically
identical i.e. clone
Individuals show variation i.e.
offspring
Mostly found in lower organisms and
is rapid.
Mostly found in higher organisms
and is gradual.
Example : Monerans,
Protistans, Fungus
Example : Some members of
Plants, Animals

A. What is the significance of reproduction?
B. Why reproduction is not considered as life
process?
C. “Life spans are not correlated with body sizes or
body organization.” Justify the statement with
the help an example from Kingdom Plantae.
D. Amoeba is considered immortal. Explain.

 Fission- (a) binary (b) multiple (c)
Plasmotomy
 Budding
 Gemmae
 Spore formation
 Fragmentation
 Vegetative propagation

 1.1 Binary Fission : Parent body into two halves.
› Single : Occur through any plane. Eg. Amoeba
› Longitudinal : Occur through longitudinal axis. Eg.
Euglena
› Transverse : Occur through transverse axis. Eg.
Paramecium
› Oblique : Plane of division is oblique. Eg. Ceratium
 1.2 Multiple Fission : Multiple daughter cells. Eg.
Plasmodium
 1.3 Plasmotomy : Multinucleate parent divides
into multinucleate daughter
cells. Eg. Opalina

 Daughter individual is formed from a small
part or bud, arising from parent body.
 Three types of budding :
› Exogenous Budding
› Endogenous Budding
› Strobilation

 The bud grows externally on the surface of
the parent body.
 It may split away from parent body or remain
attached to it for independent existence.
 Example : Hydra – Splits from parental body
Sycon – Remain attached to
parental body.

 Buds are formed within the body.
 In favourable conditions, the mass of
archaeocytes (amoeboid cells in sponges)
comes out from gemmules through
micropyle and forms new colony.
 Examples : Spongilla

 Similar segments are
repeatedly formed
by budding.
 Example : Aurelia

 Unicellular or multicellular propagules which
develop in small receptacles called Gemma
cups on the thalli (pl. thallus) and detach
from the parent to grow into new individuals.
 Example : Marchantia

 Microscopic, single celled, thin or
thick walled propagules ,
dispersive in nature and develop
into new individuals.
 Spores are formed by budding.
Types of Spores Features Example
Zoospores Motile and flagellated Chlamydomonas
Conidia Non – motile, Exogenous Penicillium
Chlamydospores Thick walled, withstand long
unfavourable conditions
Rhizopus
Oidia Small, thin walled fragments Agaricus
Sporangiospores Non – motile endospores Mucor

 Parent body breaks into two or more
fragments and each fragment develops into
a new organism.
 Example : Spirogyra, Sponges,
Echinoderms.

1. A. Name the organisms that reproduce through the structures –
Conidia & Zoospores.
B. Mention one similarity and one difference between the
two structures.
2. Differentiate between fragmentation and binary fission.
3. What is regeneration? And why sometimes is it not considered
as a mode of asexual reproduction?
4. Do unicellular organisms (one-celled living things) reproduce
using sexual or asexual reproduction?
5. What type of asexual reproduction do bacteria most
commonly use?

 Formation of new plants from vegetative parts of
plants.
 This method produces large population of clones.

Underground Stems
Subaerial or Creeping
Stems

Propagation by Cutting
Grafting
Propagation by Grafting

 Propogation of plants by culturing the cells, tissues or organs.
 Culturing results in formation of callus, that differentiates to
form a large number of plantlets.
 Eg. Chrysanthenum gladiolus

 Staminate flower :- unisexual flowers if stamen is present, it is termed as
male flower or staminate flower
 Pistilate flower :- unisexual flower if carpel/pistil is present, it is term as
female flower or pistillate flower
 Neutral flower :- if both essential whorls of flower is absent that is termed as
neutral or neuter flower
 Homothallic :- Bisexual condition in fungi and algae.
 Heterothallic :- unisexual condition in fungi and algae.
 Monoecious :- a plant may have both male and female flowers are termed as
monoecious for example maize and castor
 Dioecious :- when male and female flowers are project on different plants this
plant is known as dioecious. For example papaya, Date Palm
 Bisexual animal :- presence of both gonad female ovary and male gonads
testis in same parents is known as bisexual animal. For example sponge,
Taenia, fasciola, earthworm and leech, bisexual condition in animal is also
known as hermaphrodite
 Unisexual animal :- presence of both gonads female and male gonads in
different parents known as unisexual animal for example cockroach human
beings

Sexual
reproduction
events
Pre-fertilisation
Syngamy and
fertilisation
Post-fertilisation
Gametogenesis Gamete transfer

 Syngamy : Complete and permanent fusion of male
and female gametes to form the zygote. Eg. Humans,
Taenia etc.
 Conjugation : Organisms of same species
temporarily couple and exchange their male
pronuclei. Eg. Paramecium, Spirogyra, Bacteria.

EXTERNAL
FERTILISATION
INTERNAL
FERTILISATION
Syngamy occurs outside
of the body of organisms.
Syngamy occurs inside of
the body of organisms.
Large number of gamets
(male & female) are
released into surrounding
medium.
E.g. bony fish, amphibians
Number of ova are less, but
large number of male
gametes are formed. E.g.
birds, mammals, earthworm.

 Includes development of zygote and embryogenesis.
 Development of zygote : Development of diploid zygote
depends on type of life cycle and environmental conditions.
› Haplontic Cycle / Diplontic Cycle / Diplohaplontic Cycle
 Embryogenesis : Zygote undergoes mitotic cell division and
cell differentiation. It leads to Organogenesis. On the basis of
development of zygote, animals can oviparous or viviparous
or ovoviviparous.

OVIPAROUS VIVIPAROUS
Animals lay fertilise or
unfertilised eggs.
Give birth to young
individuals.
Eggs have calcareous shell to
protect from the harsh
environment.
No shell, they are protected
inside the mother’s body.

4/7/2016Khare.forensics@gmail.com/CBSE/XII 33
Oestrous Cycle Menstrual Cycle
The cyclic changes in the activities of
ovaries and accessory ducts as well
as hormones during reproductive
phase of non – primates.
The cyclic changes in the activities of
ovaries and accessory ducts as well
as hormones during reproductive
phase of primate mammals.
Females show irresistible sexual
urge.
Females do not show irresistible
sexual urge.
There is estrus/heat production at the
time of ovulation and copulation
occurs only at that time.
There is no estrus/heat production at
the time of ovulation and copulation
may occur at any time.
The shedding of endometrium and
bleeding do not occur. Eg. Cow, Dog,
sheep, rats, deer, tigers.
The shedding of endometrium and
bleeding occur. Eg. Monkeys, apes
and humans.

 Parthenogenesis: Female gamete develops into
new organism. Seedless fruits formed by
parthenogenesis
 Neoteny : When larva retains adult characters
such as gonads and starts producing young ones
by sexual reproduction. Eg. Ambystoma [Tiger
salamander]

 Natural Parthenogenesis
› Complete
› Incomplete
› Paedogenetic
 Artificial Parthenogenesis

 Explain importance of syngamy and meiosis in sexual life cycle of an
organism.
 Why do moss produce large number of male gametes? Provide one reason.
What are these gametes called?
 Why is whiptail lizard produce only female lizards?
 Out of many papaya plants , only few bear fruits on them. Give reason.
 Write two adaptations in animals exhibiting external fertilisation.
 Differentiate between parthenocarpy and parthenogenesis.
 ‘Viviparity limits the number of offspring in a litter’. Explain
 “Gametogenesis and meiosis are always linked”. Justify the statement.
 Why do algae and fungi shift to sexual modes of reproduction just before
the onset of adverse conditions?
 Unicellular organisms are immortal, whereas multicellular organisms are
not. Justify.
 What are the differences between perisperm and pericarp in fruit?

Biology, Teacher
Reach out – khare.forensics@gmail.com
Slideshare : khare.forensics@gmail.com
“You don’t get results by focusing on results.
You get results by focusing on the Actions that produce results.”
-- Mike Hawkins

Class12 reproduction in organisms CBSE

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