This articles provides with short revision notes for the chapter “reproduction in organisms” for students preparing for NEET Entrance Exam and CBSE Board Exam.
- Clone : Morphologically and genetically similar individuals.
- Juvenile Phase : It is the period of growth and maturity before an organism can reproduce sexually.
- Meiocytes : These are specialized cells of diploid organisms which undergo meiosis to produce gametes.
- Pericarp : It is the protective coverning of fruit, may be divided into epicarp, mesocarp and endocarp.
- Parthenogenesis : Development of an egg into an embryo without fertilisation. e.g. in rotifers, honeybees, turkey and some lizards.
- Monoecious Plants : Plants having both male and female flowers on same plant. e.g. cucurbits and coconut. The term “homothallic” is used in Fungi for same condition.
- Dioecious Plants : Plants having male and female flowers on separate plant. e.g. Papaya and date palm. The term “heterothallic”is used in fungi for the same condition.
- Oestrus Cycle : The reproductive cycle in non-primate mammals like cows, sheep, rats, deer, dogs and tigers etc;. The sexually active females reffered to as being in “heat” at a specific time of Oestrus cycle. They reabsorbs the endometrium if conception does not occur.
- Binary Fission (in single celled organism) – eg- amoeba, paramecium
- In algae, fungi and multicellular lower organisms. (Multiple Fission: e.g. Plasmodium)
>> Zoospore e.g. Chalamydomonas
>> Conidia e.g. Penicillium
>> Bud e.g. Hydra Offset
>> Gemmules e.g. Sponge
>> Fragmentation e.g. Spirogyra
>> Sporulation e.g. Amoeba, Paramoecium
>> Regeneration e.g. Hydra, Planaria
- Vegetative propagation
>> Runner e.g. Oxalis
>> Rhizome e.g. Ginger
>> Sucker e.g. Banana
>> Offset e.g. Water hyacinth
>> Bulb e.g. Onion
>> Leaf buds e.g. Bryophyllum
>> Bulbil e.g. Agave
>> Eye buds e.g. Potato
1. In Algae, Bryophytes and Pteridophytes : The male and female gametes are flagellated and motile, need a medium (water) to reach to egg.
2. In seeded plants : Pollen grains are transferred to stigma of flower of same species by various agents, like wind, water, insects, birds and ants etc.
3. In animals :
(a) By Copulation : e.g., Reptiles, Birds and Mammals.
(b) By External medium : e.g., Fishes and Amphibians.
Sporulation : During unfavourable conditions organisms like Amoeba surrounded by resistant coat (three layered hard covering) or cyst. This is called encystation. Within cyst a number of spores are formed. On returning favourable conditions, the cyst brust and spores are liberated and gradually grows in adults. This process is known as sporulation (multiple fission).
Fragmentation : It is a type of asexual reproduction where an organism splits into fragments. Their fragments develops into fully grown individual. e.g. spirogyra, fungi and some annelids.
Regeneration : It is a process of renewal, restoration and growth. It can occur at the level of the cell, tissue and organ. It is common in Hydra, Planaria and echinoderms
- In human, liver has power of regeneration, if it is partially damaged.
- During danger a lizard discard a part of its tail which can regenerate later.
Events in Sexual Reproduction
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