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Solutions for 12 Biology Chapter 1
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Class 12 Biology Chapter 1 Question Answers
Important Terms on Reproduction in Organisms
- 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 referred to as being in ‘heat’ at a specific time of Oestrus cycle. They reabsorbs the endometrium if conception does not occur.
- There are 380 chromosomes in meiocytes of a butterfly. How many chromosomes does male gamete of butterfly have?
- Which characteristic property of Bryophyllum is exploited by gardeners?
- Mention the unique flowering phenomenon exhibited by strobilanthus kunthiana (Neelakuranji).
- Mention the unique feature with respect to flowering and fruiting in bamboo species.
1. 190 chromosomes.
2. Adventitious bud arising from margin of the leaf.
3. Flower one in 12 years.
4. Flower once in their life time after 50-100 years, produce large no. of fruits and die.
5. Higher organisms have resorted to sexual reproduction in spite of its complexity. Why?
6. Bryophytes and Pteridophytes produce a large number of male gametes but relatively very few female gametes. Why?
7. (a) Why is vegetative propagation also considered as a type of asexual reproduction?
(b) Which is better mode of reproduction: Sexual or Asexual? Why?
5. Because of variations, gene pool, vigour and vitality and parental care.
6. Because male gamete need medium (water) to reach egg/female gamete. A large number of the male gametes fail to reach the female gamete. It increases the probability of fertilisation.
7. (a) Vegetative propagation takes place when new individuals arise from vegetative part of parent and have characters similar to that of parent plant.
(b) Sexual reproduction, it introduces variations in offsprings and has evolutionary significance. It helps offsprings to adjust according to the changes in environment. It produces better off springs due to character combination.