1. (c) TtWW

2. (d) all of the above

3. (a) a Chinese school boy.

4. No, since two copies of traits are inherited from parents, one from mother and the
other form father. Unless we know the nature of these two variants of traits we can
not tell which is dominant and which is recessive. Recessive traits appear when both
the parents contribute recessive allele. From this statement we can only presume are
that both parents are contributing recessive allele.

5. When we classify organism we look for similarities among organism which allows us
to group them. Based on these principles we can work out the evolutionary
relationship to the species.

6. Analogous organs: Such organs which perform similar function but are different in
structure and origin. Example- Wings of birds and wings of insects.
 Homologous organs: Such organs which may have different functions but similar
structure and origin. Example- fore arm of frog, lizard and bird.
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8. (i) Study of fossils allow us to make estimates of how far back evolutionary
relationship go between organisms.
(ii) Study of age of fossils allows us to know which organisms evolved earlier and
which later.

9. The evidence was given by Stanley L. Miller and Harold C. Urey in 1953. They
assembled an atmosphere similar to that thought to exist on early earth over water.
This was maintained by them at a temperature just below 100 degree Celcious and
sparks were passed through the mixture of gases to stimulus lightening. At the end
of week, they found that 15% of the carbon had been converted to simple
compounds of carbon including amino acids which make up protein molecules.

10. Variations arise either because of errors in DNA copying or as a result of sexual
reproduction. Due to sexual reproduction genetic variability increases in the
population from one generation to another. This happens due to the fact that
sexually reproducing organism inherits half the genes from each parent. These
variations are very important for the process of evolution.

11. No, depending on the nature of variations different individuals have been different
kinds of advantages. However, when a drastic change occurs in environment only
those organisms in the population will survive which have an advantageous
variation in that population to survive in changed environment.

12. Equal contribution of male and female parents is ensured in progeny during sexual
reproduction. Each trait of progeny is determined by a pair of alleles and gametes of
male and female contain one allele. Each allele pairs during fertilisation combine
together to determine traits. Thus, the traits of progeny are determined by equal
genes from male and female.

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