CBSE Class 12 Biology Reproduction in Organisms Notes

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Reproduction in Organisms Class 12 Biology Revision Notes

Class 12 Biology students should refer to the following concepts and notes for Reproduction in Organisms in standard 12. These exam notes for Grade 12 Biology will be very useful for upcoming class tests and examinations and help you to score good marks

Reproduction in Organisms Notes Class 12 Biology

REPRODUCTION IN ORGANISMS

Briefing of Concept
 
Life Span: Period from birth till natural death. Every organism lives only for certain period of time
Reproduction –Producing young-ones of their kind, generation after generation.
 
Types of reproduction:
 
1. Asexual reproduction: single parent capable of producing offsprings.Somatogenic reproduction.
2. Sexual reproduction : two parents are involved in producing offspring.
 
Modes of asexual reproduction
 
1. Binary fission: parent body divides into two halves, genetically identical to parent. Organisms considered immortal Amoeba: It is simple or irregular. Paramecium: Transverse binary fission.
 
2. Multiple fission: parent body divides into many daughter organisms e.g., Plasmodium.
 
3. Budding: daughter organisms grow from small buds arising in parent body. Exogenous budding: out side the body eg. Hydra, Yeast.Endogenous budding: inside the body eg. Gemmule in sponge.
 
4. Spore Formation: Exogenous spores Conidia: non-motile eg. Fungi. Zoospores: microscopic motile structures eg. Algae.
 
5. Vegetative reproduction: In plants term vegetative reproduction frequently used instead of asexual reproduction, units of vegetative propagation called vegetative propagules. Eg runner, rhizome, sucker, tuber offset, bulb give rise to new plant
 
PHASES OF LIFE SPAN.
i. Juvenile phase: The phase of growth before reproductive maturity.
ii. Reproductive phase: Reproductive maturity.
iii. Senescent phase: Phase between reproductive maturity and death.
 
The main events of sexual cycle are:
 
1. PRE-FERTILISATION EVENTS:
a. Gametogenesis :
The process of formation of male and female gametes by meiosis (cell-division).
√ Homogamete (Isogamete): - gametes similar eg. Algae
√ Heterogamete(an-isogamete): - morphologically dissimilar gamete ,male gamete (antherozoid or sperm) ,female gamete (egg or ovum) eg. Human.
 
→ Sexuality in organisms:
• In plants
 
Bisexual term is used for Homothallic and Monoecious plants: Both male and female reproductive structures in same plant eg. Higher plants, cucurbits and coconut.
Unisexual term used for Heterothallic and Dioecious plants: Male and female reproductivestructure on different plants. Male flower–staminate flower and female flower–pistillate flower eg. papaya and date-palm.
 
In Animals
Bisexual term is used for Hermaphrodite animals-eg. Earth-worm, Tape-worm, Leech,Sponge.Unisexual animals have male & female sexes in separate individuals-e.g. insects, frogs,human beings
 
→  Cell division during gamete formation:
•  Haploid-parent (n) produces haploid gametes (n) by mitotic division, eg. Monera, fungi, algae and bryophytes.
• Diploid parent (2n) produces haploid gametes(n) by meiosis division (possess only one set of chromosomes)and such specialized parent cell is called meiocyte or gamete mother cell.
 
b) Gamete transfer:- to facilitate fusion. Male gametes mostly motile and female non-motile,exception few fungi and in algae both gametes are motile in some cases.Water medium for gamete transfer- in lower plants. Large number of male gametes are produced to compensate loss. Higher plants, pollen-grains are transferred by pollination.
 
2. FERTILIZATION: Fusion of male and female gametes to produce diploid zygote.
 
Two types- external and internal
 
→ External fertilisation- outside the body of organism in external- medium (water) eg. majority of algae, fishes, amphibians.
 
Advantage-
1. Show great synchrony between the sexes
2. Release of large number of gametes into surrounding medium
2. Large number of off springs produced.
 
Disadvantage- offspring vulnerable to predators, natural disasters.
 
→ Internal fertilisation- fusion occurs inside female body eg. majority of plants and animals. Egg non-motile and formed inside female body. Male gamete motile, produced in large numbers to reach egg and fuse with it. In seed plants, non- motile male gamete carried to female gamete by pollen-tube.
 
3. POST -FERTILISATION EVENTS
 
Formation of zygote. Zygote. One celled, diploid, vital link between two generations.
 
√ Haplontic life cycle- zygote (2n) divides by meiosis to form haploid (n) spores.
√  Diplontic life-cycle- zygote (2n) divides mitotically, develops into embryo (2n).
UNDERGO MEIOSIS –HAPLOID SPORES----HPLONTIC LIFE CYCLE ZYGOTE UNDERGO MITOSIS ---DIPLONTIC LIFE CYCLE

CBSE Class 12 Biology Reproduction in Organisms Notes 1

Embryogenesis: development of embryo from zygote by cell division (mitosis) and cell differentiation. Cell- division increases the number of cells in the developing embryo
Parthenogenesis.-development into new organism without fertilisation eg. Rotifers, honey-bees,some lizard, bird(turkey).
Parthenogenesis: Female gamete develops into new organism.
 
√ Seedless fruits formed by parthenogenesis
√ Clone: A group of individuals of the same species that are morphologically and genetically similar to each other & their parents
√ Turion : Fleshy overwintering buds in aquatic plants help in perrenation Eg potomegaton, utricularia
√Bulbil : Fleshy buds that produce new plant Eg Agave and Oxalis


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Chapter 1 Reproduction in Organisms
CBSE Class 12 Biology Parthenogenesis Notes
CBSE Class 12 Biology Reproduction In Organisms Minds Map
CBSE Class 12 Biology Reproduction in Organisms Notes
CBSE Class 12 Biology Reproduction In Organisms Notes Set A
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CBSE Class 12 Biology Reproduction In Organisms Study Guide
Chapter 2 Sexual Reproduction In Flowering Plants
CBSE Class 12 Biology Sexual Reproduction In Flowering Plants Minds Map
CBSE Class 12 Biology Sexual Reproduction In flowering Plants Notes Set A
CBSE Class 12 Biology Sexual Reproduction In flowering Plants Notes Set B
CBSE Class 12 Biology Sexual Reproduction In flowering Plants Notes Set C
Chapter 3 Human Reproduction
CBSE Class 12 Biology Human Reproduction Minds Map
CBSE Class 12 Biology Human Reproduction Notes
CBSE Class 12 Biology Human Reproduction Study Guide
Chapter 4 Reproductive Health
CBSE Class 12 Biology Reproductive Health Notes Set A
CBSE Class 12 Biology Reproductive Health Notes Set B
CBSE Class 12 Biology Reproductive Health Study Guide
Chapter 5 Principles of Inheritance and Variation
CBSE Class 12 Biology Genetics Notes
CBSE Class 12 Biology Principles Of Inheritance And Variation Minds Map
CBSE Class 12 Biology Principles Of Inheritance And Variation Notes
CBSE Class 12 Biology Principles Of Inheritance And Variations Study Guide
Chapter 6 Molecular Basis of Inheritance
CBSE Class 12 Biology Molecular Basis Of Inheritance Minds Map
CBSE Class 12 Biology Molecular Basis Of Inheritance Notes Set A
CBSE Class 12 Biology Molecular Basis Of Inheritance Notes Set B
CBSE Class 12 Biology Molecular Basis Of Inheritance Study Guide
Chapter 7 Evolution
CBSE Class 12 Biology Evolution Minds Map
CBSE Class 12 Biology Evolution Notes Set A
CBSE Class 12 Biology Evolution Notes Set B
CBSE Class 12 Biology Evolution Study Guide
Chapter 8 Human Health and Diseases
CBSE Class 12 Biology Human Health And Disease Minds Map
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CBSE Class 12 Biology Human Health And Disease Study Guide
Chapter 9 Strategies for Enhancement In Food Production
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CBSE Class 12 Biology Strategies For Enhancement In Food Production Notes Set A
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CBSE Class 12 Biology Strategies For Enhancement In Food Production Study Guide
Chapter 10 Microbes In Human Welfare
CBSE Class 12 Biology Microbes In Human Welfare Minds Map
CBSE Class 12 Biology Microbes In Human Welfare Notes Set A
CBSE Class 12 Biology Microbes In Human Welfare Notes Set B
Chapter 11 Biotechnology Principles and Processes
CBSE Class 12 Biology Biotechnology Principles And Processes Notes Set A
CBSE Class 12 Biology Biotechnology Principles And Processes Notes Set B
CBSE Class 12 Biology Biotechnology Principles And Processes Study Guide
Chapter 12 Biotechnology and Its Application
CBSE Class 12 Biology Biotechnology And Its Application Minds Map
CBSE Class 12 Biology Biotechnology Its Application Notes
CBSE Class 12 Biology Biotechnology And Its Application Notes
CBSE Class 12 Biology Biotechnology Its Application Study Guide
Chapter 13 Organisms and Populations
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CBSE Class 12 Biology Organisms And Populations Notes
CBSE Class 12 Biology Organisms And Populations Study Guide
Chapter 14 Ecosystem
CBSE Class 12 Biology Ecosystem Minds Map
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CBSE Class 12 Biology Ecosystem Study Guide
Chapter 15 Biodiversity and Conservation
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CBSE Class 12 Biology Biodiversity And Conservation Study Guide
Chapter 16 Environmental Issues
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CBSE Class 12 Biology Environmental Issues Study Guide
Concepts Maps
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Other Chapters
CBSE Class 12 Biology Respiration Notes

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