The process by which new species develop from the existing species is known as speciation.
Factors leading to speciation:
(i)Geographical isolation of a population caused by various types of barriers like mountain ranges, rivers, sea etc. The geographical isolation leads to reproductive solation due to which there is no flow of genes between separated groups of population.
(ii)Genetic drift caused by drastic changes in the frequencies of particular genes by chance alone.
(iii)Variations caused in individuals due to natural selection.
(iv)Drastic change in the genes or DNA called mutation is also a cause of speciation. Reproductive isolation cannot be major factor in the speciation of a self-pollinating
plant species. This is because, it does not depend on any other plant for its reproduction process.

(a) Mendel choose garden pea for his experiment because pea plants was self fertilising and have short life cycle.
(b) Mendel performed experiments on a garden pea (Pisumsativum) with different visible contrasting characters. He selected seven contrasting pairs of characters such as tall / short plants, purple / white flower colour etc.
(c) Mendel performed his experiment on tall and dwarf plant and interpreted his results to show that the traits may be dominant or recessive. Parent plants: True breeding tall pea plant was crossed with true breeding dwarf pea plant. Production of F₁ plants: All F₁ plants were found to be tall. Results of self-pollination ofF₁ plants or F₂plants: Mendel found that on self-pollination of F₁ plants, the progenies obtained in F₂ generations were not all tall plants. Instead, one- fourth of F₂plants were found to be dwarf.
Mendel's explanation for the reappearance of the short trait: From this experiment, Mendel concluded that the F₁ tall plants were not true breeding. They were carrying
both the traits. They appeared tall, because the tall trait was dominant over the dwarf trait.

From this study, we cannot make any inference whether light eye colour trait is recessive or dominant, because as both the parents have light colour eye, all the children will definitely have light colour eye (though certain variations may occur).

Equal genetic contribution of male and female parents in the progeny is ensured by the equal inheritance of chromosome from each parent.
Human possesses 23 pairs of chromosomes, of which 22 pairs are autosomes and 1 pair is the sex chromosomnes.
The two sex chromosomes in human are X and Y. Females have 2X chromosomes and males have a X and Y chromosome.
During the process of fertilization, a haploid sperm fuses with a haploid ovum to produce a diploid zygote. Zygote receives equal amount of genetic material from each parent and thus, retains the diploid narure on fertilizarion.

The presence of feathers in dinosaurs and birds indicates that they are evolutionarily related. Dinosaurs had feathers not for flying but instead these feathers provided
insulation to these warm-blooded animals. However, the feathers in birds are used for flight. This proves that reptiles and birds are closely related and that the evolution of
wings started in reptiles.

(a) They have common ancestry.
(b) Homologous organs

Evolution shows that body design changed from simple to complex. Hence, bacteria has the simplest body design and chimpanzee has the most complex and better body design.

The small number of tigers are causing a worry for the genetics because if they become extinct then the genes of this species will be lost forever. There will be no scope of again getting this species back to life without their genes.

It is believed that features in dinosaurs might have provided insulation in cold weather but later on became useful for flights in birds.

RrYy (Round yellow).

(a) Round yellow
(b) Round yellow, Round green, Wrinkled yellow, Wrinkled green.
(c) Wrinkled green
(d) Round yellow.

(a) The structures which have a common basic structure but perform different functions are called homologous structures. Example-fore limbs of reptiles, amphibians and mammals.
(b) Yes.

TT

Female baby

(i) Doctor will tell them that the sex of the baby can be known by this test.
(ii) Even he knows the sex of the baby he will not disclose it to the couple.
(iii) If the couple knows the sex of the baby and in case it is a female child they may try to get it aborted. Hence it is moral duty of the doctor not to divulge the sex of the unborn baby.

(a) No, she should not take the medicine.
(b) Of course she should visit a doctor to get information.
(c) She is having 50% chances of having a male child as 50% sperms carry Y chromosome and 50% X chromosome.