CBSE Class 12 Biology Reproduction In Organisms Notes Set C

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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

Unit VI
Chapter-1
Reproduction in organisms

Sporulation

When the products of multiple fission become individually surrounded by resistant coats, the cyst walls before their release from the parent, the processs is known as sporulation and the encysted products are termed spores. The spores remain inactive during unfavorable conditions such as dessication and extremes of temperature. When condition becomes favorable, the cyst hatches and gradually grows into an adult. Sporulation is thus not only a mean of reproduction, but also enables the organism to survive during unfavorable conditions and disperse to new localities with air. It occurs in amoeba.

class_11_chemistry_concept_23

It is the condition where a person receives two copies of a chromosome or part of a chromosome, from one parent and no copies from the other. 

Fragmentation

Fragmentation is a form of asexual reproduction where an organism splits into fragments. Each of these fragments develops into mature fully grown individual followed by mitosis. it occurs in some algae (Spirogyra), fungi, some annelids and sea stars.

Regeneration

Regeneration is the process of renewal, restoration and growth. It can occur at the level of the cells, tissues and organs. It is common in Hydra, planarian flatworm and echinoderms. A lizard can discard a part of tail when in danger, and the tail can regenerate later. In humans too the liver can regenerate if partially damaged.

Very Short Answer Questions

Question. Is Marchantia monoecious or dioecious? Where are the sex organs borne in this plant? 
Answer. Marchantia is dioecious. The male sex organs, antheridia, are borne on the antheridiophores and female sex organs, called as archegonia are borne on archegoniophores.

Question. Write the two pre-fertilisation events from the list given below: Syngamy, Gametogenesis, Embryogenesis, Pollination
Answer. Gametogenesis, Embryogenesis, Pollination.

Question. Which is a better mode of reproduction: sexual or asexual? Why?
Answer. Sexual mode of reproduction is better because it is biparental reproduction and introduces variation among offsprings and their parents (in a population) due to crossing over and recombination during gamete formation by meiosis and thus helps in better adaptation to changing environment.

Question. How is it possible in Oxalis and Viola plants to produce assured seed-sets even in the absence of pollinators?
Answer. By presence of cleistogamous flowers, hence anthers and stigma lie close to each other ensuring self-pollination.

Question. Mention the unique feature with respect to flowering and fruiting in bamboo species.
Answer. Bamboo species flower once in its life time generally after 50–100 years of vegetative growth. It produces large number of fruits and then dies.

Short Answer Questions

Question. A liverwort plant is unable to complete its lifecycle in a dry environment. State two reasons. 
Answer. For sexual reproduction to take place in mosses and liverworts the motile male gametes,antherozoids, have to swim on the water surface to fertilise the immotile female gametes, egg.
In dry conditions, the antherozoids do not reach the egg and hence fertilisation cannot occur. So, the life cycle remains incomplete.

Question. Name the relationship between the first two words and suggest a suitable word (a) Doob grass : Runner : : Potato : ………… (b) Endogamy : Self-fertilisation : : Exogamy : …………
Answer. (a) Tuber (b) Cross-fertilisation.

Question. Mosses and frogs both need water as a medium for fertilisation. Where does syngamy occur and how is it ensured in both these organisms?
                                                                                      OR
Write the basis of categorising animals as oviparous or viviparous, giving one example of each.
Answer. In frogs, external fertilisation takes place in water. The frogs release large number of motile gametes. There is synchronised maturation of ova and sperms. In moss, internal fertilisation takes place. The male gametes are motile and are produced in large numbers.
                                                                                      OR
Oviparous animals are egg laying (fertilised or unfertilised). For example, reptiles, birds.
Viviparous animals give birth to young ones. For example, majority of mammals; humans.

Question. Why dogs and cats have oestrus cycle but human beings have menstrual cycle, though all are mammals? 
Answer. Dogs and cats are seasonal breeders . They have heat period during which ovulation takes place.
Humans, on the other hand, have this cycle monthly.

Question. A single pea plant in your kitchen garden produces pods with viable seeds, but the individual papaya plant does not. Explain. 
Answer. Flowers of pea plants are bisexual, hence can be self pollinated and produce pods with viable seeds.
Papaya is a dioecious plant bearing male and female flower on separate plants. It is unable to produce viable seeds as there is no cross-pollination. It could be a male plant which is unable to produce fruit and seeds.

Question. With which type of reproduction do we associate the reduction division? Analyse the reasons for it. 
Answer. Reduction division is associated with sexual reproduction because the diploid organisms undergo meiosis to form haploid gametes.

Long Answer Questions

Question. Differentiate between an annual and a biennial plant. Provide one example of each.
Answer.

S.No.              Annual plants                                                  Biennial plants
(i)These plants require a single season to complete their whole life cycle.These plants require two seasons to complete their whole life cycle.
(ii)They grow, set seeds and die within one year.In the first year, they grow a healthy root system and short stem, i.e., show vegetative growth and become dormant in winters. In second year, they grow quickly, flower, set seeds and die.
(iii)For example, rice, wheat, etc.For example, onion, carrot, etc.

Question. Although sexual reproduction is a long drawn, energy-intensive complex form of reproduction, many groups of organism in Kingdom Animalia and Plantae prefer this mode of reproduction. Give at least three reasons for this. 
Answer. (a) Sexual reproduction brings about variation in the offspring.
(b) Since gamete formation is preceded by meiosis, genetic recombination occurring during crossing over (meiosis-I), leads to a great deal of variation in the DNA of gametes.
(c) The organism has better chance of survival in a changing environment.

Question. Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?
Answer. In viviparous animals, the young one develops inside the body of the female organism. As a
result of this, the young one gets better protection and nourishment for proper development. In case of oviparous animals, they lay eggs and the young ones develop inside the calcareous shell, outside the body of the female. So, the young ones are not effectively protected and nourished and are vulnerable to predators. So, they are at a greater risk as compared to the offsprings of the viviparous animals.

  

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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
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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
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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
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CBSE Class 12 Biology Biotechnology Principles And Processes Study Guide
Chapter 12 Biotechnology and Its Application
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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 Study Guide
Chapter 14 Ecosystem
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CBSE Class 12 Biology Ecosystem Study Guide
Chapter 15 Biodiversity and Conservation
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Chapter 16 Environmental Issues
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Concepts Maps
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Other Chapters
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