1.What is Reproduction?
Ans: Reproduction is defined as a biological process in which an organism gives rise to young ones (offspring) similar to itself.The offspring grow, mature and in turn produce new offspring. Thus, there is a cycle of birth, growth and death. Reproduction enables the continuity of the species, generation after generation.
2.What is asexual reproduction?
Ans: When offspring is produced by a single parent with or without the involvement of gamete formation, the reproduction is asexual.Asexual reproduction is common among single-celled organisms, and in plants and animals with relatively simple organisations. The most common asexual reproductive structures are conidia (Penicillium), buds (Hydra) and gemmules (sponge).
3.What is the cause of variations in animals reproducing asexually?
Ans:In asexual reproduction a single individual (parent) is capable of producing offspring.The offsprings produced are genetically identical to the parent. The variations are seen sometimes and that is mostly due to mutation that occurs during cell division and because of that the offspring differs from the parent cell.
4.Under which group of organisms is asexual reproduction more common?
Ans:Asexual reproduction is common among single-celled organisms(e.g., Amoeba, Paramecium), and in plants and animals with relatively simple organisations.
5.Why are male gametes produced in large quantities in most organisms?
Ans:A large number of the male gametes, however, fail to reach the female gametes. To compensate for this loss of male gametes during transport, the number of male gametes produced is several thousand times the number of female gametes produced.
6.What is Sexual reproduction?
Ans: When two parents (opposite sex) participate in the reproductive process and also involve fusion of male and female gametes, it is called sexual reproduction.
7.What is binary fission?
Ans: The organisms in which cell division is itself a mode of reproduction is called as Binary fission .Examples are Amoeba, Paramecium.
8. Explain vegetative propagules.
Ans:In plants, the units of vegetative propagation such as runner, rhizome, sucker, tuber, offset, bulb are all capable of giving rise to new offspring .These structures are called vegetative propagules.
9.What is gametogenesis ?
Ans:Gametogenesis refers to the process of formation of the two types of gametes – male and female. Gametes are haploid cells.
10.What is homogametes?
Ans:In some algae the two gametes are so similar in appearance that it is not possible to categorise them into male and female gametes.They are hence, are called homogametes (isogametes).
11.What is bisexual reproduction?
Ans:The species which possess both the reproductive organs i.e male and female are said to be bisexual. Earthworms, (Figure 1.6a) sponge, tapeworm and leech, typical examples of bisexual animals that possess both male and female reproductive organs, are hermaphrodites.
12.What is unisexual reproduction?
Ans:In this case the organism or species are either male or female. They produce male or female sex cells but noth both.
13.What is "terror of bengal"?
Ans:The "terror of Bengal" are water bodies i.e aquatic plant ‘water hyacinth’ which is one of the most invasive weeds found growing wherever there is standing water. It drains oxygen from the water that leads to death of fishes. It grows fast and also spreads all over the water body in a short period of time and becomes very difficult to get rid of.
14.Explain juvenile phase.
Ans:All organisms have to reach a certain stage of growth and maturity in their life, before they can reproduce sexually. That period of growth is called the juvenile phase.
15.Explain oestrus cycle.
Ans:The females of placental mammals exhibit cyclical changes in the activities of ovaries and accessory ducts as well as hormones during the reproductive phase. Such cyclical changes during reproduction are called oestrus cycle.It is seen in non-primate mammals like cows, sheep, rats, deers, dogs, tiger, etc.
16.What is heterogametes?
Ans:In a majority of sexually reproducing organisms the gametes produced are of two morphologically distinct types and are called heterogametes. In such organisms the male gamete is called the antherozoid or sperm and the female gamete is called the egg or ovum.
17.Why do zygotes in Fungi develop a thick wall?
Ans:The development of the zygote depends on the type of life cycle the organism has and the environment it is exposed to.The zygote in fungi develops a thick wall so that it gets resistant to desiccation and damage in water. It undergoes a period of rest before germination.
18.Vegetative reproduction is a special kind of asexual reproduction. Justify
Ans:Vegetative reproduction such as runner, rhizome, sucker, tuber, offset, bulb are all capable of giving rise to new offspring.The formation of these structures does not involve two parents and hence the process involved is asexual reproduction.
19.Discuss the process of reproduction in yeast.
Ans:Reproduction in yeast is asexual as single parent is involved.The single cell division is unequal and small buds are produced that remain attached initially to the parent cell which eventually gets separated and mature into new yeast organisms (cells).
20.Describe any 2 unusual flowering patterns in plants.
Ans: