1. Explain the following terms:-
(a) Reproduction- The process of giving rise to new organisms of the same species.
(b) Fertilization-The fusion of male & female gametes.
(c) Zygote- The single-celled structure formed on the fusion of male & female gametes.
(d) Metamorphosis- The gradual transformation of an organism from one form to another during its life cycle
(e) Hermaphrodites-The organisms having both male & female reproductive organs in the same body. Eg:- Earthworm, Leech
(f) Foetus- The multicellular structure formed after the repeated cell divisions in the Zygote formed as a result of fertilization.
(g) Larva- The active form that emerges from the eggs .
(h) Placenta- The specialized tissue that attaches the developing foetus to the uterine wall & provides for it nourishment, respiration & excretion.
2. Give reasons for the following:-
(a) Gender of the resulting offspring is determined by the male parent in humans.
Ans- The Y-chromosome bearing sperm that fertilizes an ovum results in a male offspring.
The X-chromosome bearing sperm that fertilizes an ovum results in a female offspring.
(b) Sex hormones regulate secondary sexual characters.
Ans- The functioning of our reproductive organs is regulated by the sex hormones and one of the functions is the appearance of secondary sexual characters at puberty.
(c) Platypus & Echidna lay eggs but are not oviparous animals.
Ans- They lay eggs but feed the young ones on milk through the mammary glands.
(d) Sperm needs to have motility.
Ans – Sperms have to enter the female reproductive passage and fertilize the ovum by travelling through the vagina & uterus for this in the fallopian tube/ oviduct.
LONG ANSWER TYPE QUESTIONS:-
1. Explain where the embryo stays till it is fully developed and also explain how its nutritional , respiratory & excretory functions are carried out.
Ans- The embryo gets attached to the uterine wall through the Placenta which is a specialized tissue richly supplied by blood & takes care of all the developmental functions of the developing embryo- nutrition, respiration & excretion.
2. What is Asexual reproduction? What are the advantages of this method?
Ans- The mode of reproduction that involves a single organisms & also doesn’t require any special organs or cells. Its advantages are:-
(a) Offsprings produced are identical to the parents so desired traits can be transmitted to the next generation
(b) A quick method of reproduction
(c) Only one parent organism is required, no special organs or cells also required.
3. Explain the meaning of Binary Fission. Name a few organisms that reproduce like this & draw a series of diagrams to demonstrate this process in Amoeba.
Ans- The method by which an organism divides into two equal halves .
Other organisms are:- Paramecium, Euglena, Bacteria. Refer to figure 9.12 of NCERT
4. Explain how budding occurs. Name a few organisms that reproduce like this & draw a series of diagrams to demonstrate this process in Hydra.
Ans- Small bulges appear on the sides of the body of the organisms that gradually develop into new organisms. Sponges & Yeast besides Hydra.
Refer to figure 9.11 of NCERT
5. What is Metamorphosis? With the help of flow diagrams illustrate the life cycles of a Silkworm & Frog.
Ans- Metamorphosis- The gradual transformation of an organism from one form to another during its life cycle.
Silkworm:- Egg -->Larva/ Caterpillar--->Pupa/ Cocoon---> Adullt
Frog:- Egg---> Tadpole(Larva)- --> Froglet- --> Adult Frog
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