The major evolutionary trend of horses

(i) General increase (with occasional decrease) in size. (ii) Progressive loss of toes.

(iii) Lengthening of toes that are retained.

(iv) Lengthening of limbs in general.

(v) Enlargement of brain (especially cerebral hemisphere).

(vi) Increase in the height.

(vii) Increase in the complexity of molar teeth and an enlargement of the last two and, eventually, the last three premolars until they came to resemble molars.

Evolution of horse. Top row shows change in form and size of the body. Second row show reduction in lateral toes of hind and forelimbs. The right figure in each set of two is of the forefoot, the left of the hindfoot. Third row shows change in form and size of skull. Q. 5. Distinguish between microevolution and macroevolution. Narrate the significance of population genetics in evolution.

Ans. Evolution on the grand scale of geological time, is called macroevolution while evolution at genetic level is microevolution. Microevolution is actually operative at genetic level change.

Significance of Population Genetics

The gene frequency of a population is called population genetics. Evolution occurs within populations as the relative frequencies of different variations of DNA change over time. If genes change, then enzymes automatically change and represent two different forms of individuals and definitely result in evolution.