biology class 12 chapter 1 reproduction in organisms

1. PREPARED BY
YOONUS ALI
PGT BIOLOGY
1
(CHAPTER 1)

2. LIFE SPAN- TIME DURATION FROM BIRTH TO DEATH
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
Banyan tree 200 years
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3. REPRODUCTION
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 The process in which organisms produce new
organism of same kind is called reproduction.
 Reproduction is the essential process as it
responsible for the continuity of life on the earth.
 If any species has lost the power of reproduction
then it will be eliminated from the life

4. TYPES OF REPRODUCTION
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. It has no role
in evolution.
Individuals show variation i.e.
offspring. It helps in evolution.
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5. ASEXUAL REPRODUCTION AND
TYPES OF ASEXUAL
REPRODUCTION
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 The reproduction in which only one parent can
produce new offspring without involvement of
gametes.
 Types of asexual reproduction-
 Fission- (a) binary (b) multiple
 Budding
 Spore formation
 Fragmentation and regeneration
 Vegetative propagation

6. Fission: it is of two types-
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 1. binary fission- when the body of organism
divided into two offsprings. Several unicellular
organisms reproduce by this process. It may be
irregular, longitudinal and transversal according
to plane of division. e.g. protist and bacteria.
 2. multiple fission- when the body of organism
divided into several offsprings. Plasmodium is
the example.
 Sporulation is occurs in unfavorable condition in
amoeba cover themselves by cyst, called
encystation. On return of unfavorable condition
several daughter nuclei released in water and
produced several offsprings.

7. Binary fission in Amoeba and multiple fission in
plasmodium
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8. Spore formation-
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 Motile microscopic zoospores -(chlamydomonas).
These have two flagella.
 Conidia (penicillium)- non motile. May be single (or in
chain(pencillin). Produced on conidiophore. Produce
externally
 Gemmules- (sponges)- asexual reproductive bud.
Produced internally.

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10. Budding-
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 Bud is an outgrowth from any part of the parent
body.
 When it grows it separated from the parent body and
develop into new organism.e.g. Yeast, Hydra.

11. VEGETATIVE PROPAGULES-when the
old part of plant produce new plants.
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 Runner- oxalis
 Sucker
 Tuber- potato
 Offset- water hyacinth, pistia
 Bulb- onion, garlic
 Rhizome- ginger
 Bulbil- agave
 Leaf buds- Bryophyllum

12. Terror of bengal
 The plant water hyacinth (Eichhornia crassipes) is
nicknamed as the "Terror of Bengal" because it
grows at an alarming rate and spreads on the
surface of the water body. This cut out of the light
and it also causes an increase in the oxygen
demand. Thus, causing the death of fishes and
other aquatic organisms.
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13. SEXUAL REPRODUCTION
Sexual
reproduction
events
Pre-fertilisation
Syngamy and
fertilisation
Post-fertilisation
Gametogenesis Gamete transfer
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14. Stages in sexual reproducing
organism
 There are three phases in life o sexual
reproducing organisms
 Juvinile phase – it is phase of growth.
 Reproductive phase- reproductive organs start to
produce gametes.
 Senscense phase- body become weak and end
at the death of the organism
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15. Flowering in Plants
 : In yearly and half-yearly plants, floweringoccurs
only once or twice a year. In these plants
vegetative, reproduction and senescent stage are
unmistakably distinguished. Case: Rice, Wheat,
marigold and so on.
 In a few plants blooming happens a few times in
a specific season. In a few plants blossoming
happens just once in a life time. After that plants
dies.
 For Instance, Bamboo blossoms following 50 to
100 years. Kuranji (Strobilanthus kunthiana)
blooms once in 12 years.REPRODUCTION IN ORGANISM- CLASS XII
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16. PRE-FERTILISATION CHANGES
(a) gametogenesis
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 It is the process of formation of haploid male and
female gametes.
 Gametes may be homogametes (isogametes)
or heterogametes.
 In heterogametes the male gamete is called
antherozoid or sperm and the female gamete is
called the ovum.

17. PRE-FERTILISATION CHANGES
(a) gametogenesis
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 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.
 Homogametes or Isogametes: These are
morphologically comparative female and male
gametes.
 Heterogametes: These are morphologically
unique female and male gametes.
 Anthrozoid or Sperm is themale gamete

18. PRE –FERTILIZATION CHANGES
(b) gamete transfer
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 Fusion of male and female gamete is called
fertilisation.
 So male and female gamete must be brought
together.
 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

19. Condition of flowers
 Male flower is staminate and bears only stamens.
 Female flower is pistillate and bears only pistils.
 Example for Monoecious Plants
Includes: Cucurbita.
 Example for Diecious Plants Includes: Papaya,
Date Palm.
 Sexuality in Animals -Hermaphrodite or
Bisexual Animals: Creatures having both male
and female regenerative organs
 Unisexual Animals: Creatures having just male or
female regenerative organ
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20. PRE –FERTILIZATION CHANGES
(b) gamete transfer
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 Pollination is the method of gamete transfer in
higher plants as pollen grains contain male
gametes.
 The number of male gametes are thousand times
the number of female gametes as there is loss of
male gametes during transfer.
 In dioecious animals there is special mechanism
for gamete transfer.

21. SYNGAMY AND FERTILISATION
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 It results in the formation of diploid zygote.
 In some animals like rotifers, honey bees, some
lizards and birds (turkey) female gametes develop
in to organism without fertilisation, such a
phenomenon is called parthenogenesis.

22. POST-FERTILISATION EVENTS
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 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.

23. POST-FERTILISATION EVENTS
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 Organisms showing haplontic life cycle, zygote
undergoes meiosis. While organisms showing
diplontic life-cycle undergoes mitosis.
 The zygote develops into an embryo.
 Embryogenesis involves (i) cell division (ii) cell
enlargement or growth (iii) cell differentiation.
 In oviparous animals zygote development occurs
outside of female’s body, they are egg laying e.g.
reptiles, birds.

24. POST-FERTILISATION EVENTS
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 In viviparous animals zygote development occurs
inside of female’s body. They give birth to young
individuals. E.g. mammals
 In plants zygote is formed inside ovule, where it
develops into embryo, then ovule becomes seed
and ovary into fruit.
 Germination of seeds produce new plants.

25. TYPES OF FERTILISATION
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.
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26. TYPES OF ANIMALS
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.
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