CBSE Class 12 Biology Reproduction In Organisms Notes Set A

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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

 

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• REPRODUCTION IN ORGANISMS 


  Life Span 


  Period from birth till natural death.Every organism lives only for certain period of time Eg Elephant 60 -90 years, Fruit fly 4-5 weeks. Every organism live only for a certain period of time. 

• Reproduction –Producing young-ones of their kind, generation after generation. 


Types of reproduction: 


Asexual reproduction :single parent capable of producing offspring. Somatogenic reproduction 

Sexual reproduction :two parents are invovled in producing offspring. 


Modes of asexual reproduction 


 Binary fission: parent body divides into two halves, genetically identical to parent. 


• Amoeba: It is simple or irregular. Paramoecium: Transverse binary fission. Organisms considered immortal 


 Multiple fission: parent body divides into many daughter organisms : Plasmodium. 


  Budding: daughter organisms grow from small buds arising in parent body. 

Exogenous budding: out side the body eg. Hydra, Yeast. 

Budding in Yeast Endogenous budding : inside the body eg. Gemmule in sponge. Oidia of rhizopus 


 Conidia: non-motile, exogenous spores in chains eg. Fungi. 


 Zoospores: microscopic motile structures eg. Algae. 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 


  All organisms show remarkable similarity. Vast difference in their reproductive structure. Similar pattern or phases in their life cycles 


  PHASES OF LIFE SPAN. 

  Juvenile phase: The phase of growth before reproductive maturity. 

  Reproductive phase: Reproductive maturity. 

 Senescent phase: Phase between reproductive maturity and death. 

• The main events of sexual cycle are: 

i. Prefertilisation 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 reproductive-structure on different plants.

Flowering plants – male flower–staminate flower and female flower–pistillate flower eg. papaya and date-palm.

 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, humanbeings

 

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.

CBSE Class 12 Biology - Reproduction In Organisms

 

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 produced to compensate loss

 Higher plants, pollen-grains are transferred by pollination.

 Fertilization: Fusion of male and female gametes diploid zygote.

 Parthenogenesis.-development into new organism without fertilisation eg. Rotifers, honey-bees, some lizard, bird(turkey).
Fertilization Two types- external and internal .
1. Release of large number of gametes into surounding medium
2. Large number of offsprings 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. 

Post -fertilisation events- formation of zygote.
a. Zygote. One celled , diploid, vital link between two generations.

• External fertilization –zygote formed in external medium water eg. Frog,

• Internal fertilization –zygote formed inside the body eg. Humanbeings. Development of zygote depends on type of life cycle and environment. Some develop thick wall ( prevent damage and desiccation) & undergo period of rest eg. Algae, fungi.

• Haplontic life cycle- zygote (2n) divides by meiosis to form haploid (n) spores.

• Diplontic life-cycle- zygote (2n) divides mitotically, develops into embryo (2n).

• Oviparous animals lay eggs out-side the female body.Eggs can be fertilized/ unfertilized. Fertilized eggs covered which hard calcareous shell, laid in safe place in the environment. Unfertilised eggs laid in water. Example- fishes, frogs, reptiles, birds

• Viviparous animals bear and rear the embryo inside female body, give birth to youngones.
Advantage- proper embryonic care, protection, survival chances of young-ones greater.
Example- cows, whales, humanbeings

• Embryogenesis: development of embryo from zygote by cell division (mitosis) and cell differentiation.

♦ Cell- division increases the number of cells in the developing embryo Cell differentiation - groups of cells undergo certain modifications for the formation of different kinds of tissues and organs.

• In flowering plants- zygote formed inside ovule

♦ Changes occur in flowering plants:

CBSE Class 12 Biology - Reproduction In Organisms

 

• 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 aqatic plants help in perrenation Eg potomegaton, utricularia

• Bulbil :Fleshy buds that produce new plant EgAgave 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
CBSE Class 12 Biology Reproduction In Organisms Notes Set B
CBSE Class 12 Biology Reproduction In Organisms Notes Set C
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
CBSE Class 12 Biology Human Health And Disease Notes Set A
CBSE Class 12 Biology Human Health And Disease Notes Set B
CBSE Class 12 Biology Human Health And Disease Study Guide
Chapter 9 Strategies for Enhancement In Food Production
CBSE Class 12 Biology Strategies For Enhancement Of Food Production Minds Map
CBSE Class 12 Biology Strategies For Enhancement In Food Production Notes Set A
CBSE Class 12 Biology Strategies For Enhancement In Food Production Notes Set B
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 And Its Application Notes
CBSE Class 12 Biology Biotechnology Its Application Notes
CBSE Class 12 Biology Biotechnology Its Application Study Guide
Chapter 13 Organisms and Populations
CBSE Class 12 Biology Organisms And Populations Minds Map
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
CBSE Class 12 Biology Ecosystem Notes Set A
CBSE Class 12 Biology Ecosystem Notes Set B
CBSE Class 12 Biology Ecosystem Study Guide
Chapter 15 Biodiversity and Conservation
CBSE Class 12 Biology Biodiversity And Conservation Minds Map
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CBSE Class 12 Biology Biodiversity And Conservation Study Guide
Chapter 16 Environmental Issues
CBSE Class 12 Biology Environmental Issues Minds Map
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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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