Q. 1 What is Reproduction?
A.1. Reproduction is defined as a biological process in which an organism gives rise to young ones (offspring) similar to itself.
Q. 2 what is Life Span?
A. 2 The period from birth to the natural death of an organism represents its life span.
Q. 3.Why is Reproduction Necessary?
A.3 Reproduction enables the continuity of the species, generation after generation. Genetic variation is created and inherited during reproduction.
Q.4. Define External Fertilisation. What are its disadvantages?
A.4 When syngamy occurs in the external medium (water), i.e., outside the body of the organism. This type of gametic fusion is called external fertilisation. eg. In majority of algae and fishes as well as amphibians, in most aquatic organisms.Organisms exhibiting external fertilisation show great synchrony between the sexes and release a large number of gametes into the surrounding medium (water) in order to enhance the chances of syngamy. This happens in the bony fishes and frogs where a large number of offspring are produced. A major disadvantage is that the offspring are extremely vulnerable to predators threatening their survival up to adulthood.
Q.5. Name any 2 unisexual plants.
A.5. Papaya & Date Palm – Unisexual Plants.
Q. 6 Distinguish between Monoeciuos plants and Dioecious Plants.
A.6.
|
MONOECIOUS PLANTS |
DIOECIOUS PLANTS |
|
Bisexual |
Unisexual |
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Both male and female reproductive stuctures in the same plant |
Only one of the reproductive structures on one plant |
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Flower is bisexual |
Flower is staminate or pistillate |
|
eg. cucurbits and coconut |
eg. Papaya & Date Palms |
Q. 7. Why are offsprings of oviparous animals at a greater risk of survival?
A.7. In Oviparous animals, the fertilised eggs covered by hard calcareous shell are laid in a safe place in the environment after a period of incubation young ones hatch out.
The developing embryo is not protected within the body of female organism. Thus, as the embryo is not protected by its parent it is an easy prey to predators.
Q. 9. Which of the following is Monoecious or Dioecious organism? Earthworm, cockroach, date palm.
A. 9. Earthworm – monoecious, cockroach – dioecious, date palm – dioecious.
Q. 10. Name the vegetative propagule in – Bryophillum, Agave, Potato, water Hyacinth
A. 10. Vegetative propagule of –
Bryophillum – Adventitious buds
Agave – Bulbil
Potato – Tuber
Water Hyacinth – offset
Q.11. What does angiosperm develop into after fertilisation?
A. 11 Angiosperm develops into a zygote after fertilisation. Zygote further undergoes mitotic divisions and differentiation to form an embryo. The ovary develops into fruit and ovules develop into seed.
Q. 12. Name the different parts of Pericarp.
A.12. The pericarp has 3 layers – outer epicarp, middle mesocarp and inner endocarp.
Q. 13. Honey bee produces young ones by sexual reproduction inspite of this the colonies have haploid and diploid individual. What are the haploid individuals called?
A.13.worker bees are haploid
Q. 14. Which type of reproduction we find reduction division? How is it useful?
A.14. During sexual reproduction of diploid organisms meiosis occurs for gametogenesis.The organisms belonging to pteridophytes, gymnosperms, angiosperms and most of the animals including human beings, the parental body is diploid. It is obvious that meiosis, the reduction division, has to occur if a diploid body has to produce haploid gametes. This is important for maintaining of chromosome number of a species as zygote is formed by fusion of gametes. If gametes were also diploid their fusion would result in 4n number of chromosomes.
In diploid organisms, specialised cells called meiocytes (gamete mother cell) undergo meiosis. At the end of meiosis, only one set of chromosomes gets incorporated in gametes.