Reproduction in Organisms Subjective
- Name the vegetative propagules in the following:
(a) Agave (b) Bryophyllum
Ans – The vegetative propagules are as follow:
(a) In Agave – Bulbil
(b) In Bryophyllum – Leaf buds/adventitious buds
- Write the name of the organism that is referred to as ‘Terror of Bengal’.
Ans – Water hyacinth is referred to as the ‘Terror of Bengal’.
- Give one example of a plant that reproduces by
(a) runner (b) offset
Ans – Below is the example of a plant that reproduces by
(a) runner – Oxalis
(b) offset – Pistia
- Name an organism, where cell division in itself is a mode of reproduction.
Ans – In unicellular organisms like Amoeba, bacteria, etc., cell division in itself is a mode of reproduction
- Name an alga that reproduces asexually through zoospores. Why are these reproductive units so called?
Ans – Chlamydomonas is an alga that reproduces asexually through zoospores.Due to mobility (motile), these are referred to as zoospore.
- Name the type of cell division that takes place in the zygote of an organism exhibiting haplontic life cycle.
Ans – Meiosis is the type of cell division that takes place in zygote of an organism exhibiting haplontic life cycle.
- A moss plant produces a large number of antherozoids but relatively only a few egg cells. Why?
Ans – The antherozoids or male gametes in moss plants are motile and depend on water for transport towards female gametes (non-motile). During gamete transfer, large number of male gametes are lost. Thus, to ensure fertilisation,large number of male gametes are released to reach the non-motile female gametes.
- Why are papaya and date palm plants said to be dioecious, whereas cucurbits and coconut palms monoecious, inspite of all of them bearing unisexual flowers?
Ans – Papaya and date palm plants are said to be dioecious because male and female flowers are borne on separate plants, whereas cucurbits and coconut palms are monoecious because male and female flowers are borne on the same plant.
- What is the major difference you observe in the offsprings produced by asexual reproduction and in the progeny produced by sexual reproduction?
Ans – Offsprings – produced by asexual reproduction are genetically identical to parents and to each other. On the contrary, progeny produced as a result of meiosis and gametic fusion in sexual reproduction show variations and differences from the two parents as well as among themselves.
- Coconut palm is monoecious,while date palm is dioecious. Why are they so called?
Ans – Coconut palm is monoecious because both male and female flowers are borne on the same plant.Date palm is dioecious because these plants bears exclusively either male or female flowers.
- Name any two organisms and the phenomenon involved where the female gamete undergoes development to form new organisms without fertilisation.
Ans – Parthenogenesis is the phenomenon in which a female gamete directly develops into a new organism. It is seen in some birds (Turkey), rotifers and honeybee.
- Why do algae and fungi shift to sexual mode of reproduction just before the onset of adverse conditions?
Ans – Organisms such as fungi and algae switch to sexual mode of reproduction during adverse conditions because asexual reproduction produces a large population that may not survive due to lack of resources. Sexual reproduction also brings variation into the individuals, some of which might help the individuals to better adapt to the changed conditions and survive. This ensures the continuity of species.
- How does Penicillium reproduce asexually?
Ans – Penicillium reproduces asexually by conidia formation, which is quite commdn in fungi
- Offsprings produced by asexual reproduction are called clones. Justify giving two reasons.
Ans – Offsprings produced by asexual reproduction are called clones, because
(i)they are morphologically similar to their parent.
(ii) they have same genetic composition as their parent.
- Mention a characteristic feature and a function of zoospores in some algae.
Ans – (i) Characteristic feature Zoospores are motile, microscopic and thin-walled
(ii) Function Zoospores are asexual reproductive structures, which help in multiplication of algae
Reproduction is a seasonal phenomenon, in few organisms.
(i) Based on the seasonality in reproduction in majority of plants, following categories can be made:
Monocarpic plants Flowering occurs once in their life cycle, bear fruits and die, e.g. annuals like rice, wheat; biennials like radish, henbane, etc.
Polycarpic plants Flowering occurs every year in a particular season after reaching maturity, e.g. mango, apple, orange, etc.
Similarly, in animals, the categories are:
Seasonal breeders Breed at a particular time of the year, e.g. frogs, lizards, birds, etc.
Continuous breeders Reproduce throughout their lifespan of sexual maturity, e.g. cattle, poultry, rabbit, etc.
(ii) Cyclic changes in reproductive system of females in mammals during reproductive phase are:
In non-primate mammals, e.g. cow, sheep, rat, deer, dog, tiger, etc., these cyclic changes during reproduction are termed as oestrus cycle.
In primate mammals, e.g. monkeys, apes and humans, these cyclic changes are termed as menstrual cycle.