Question

Using various resources such as your school library or the internet and discussions with your teacher, trace the evolutionary stages of any one animal say horse.

Answer 1

The evolution of the horse started with Eohippus during the Eocene period. It involved the following evolutionary stages.

1. Gradual increase in body size.
2. Elongation of the head and neck region.
3. Increase in the length of limbs and feet.
4. Gradual reduction of lateral digits.
5. Enlargement of the third functional toe.
6. Strengthening of the back.
7. Development of the brain and sensory organs.
8. Increase in the complexity of teeth for feeding on grass.

The evolution of the horse is represented as:

1. Eohippus: It had a short head and neck. It had four functional toes and a splint of 1 and 5 on each hind limb and a splint of 1 and 3 in each forelimb. The molars were short-crowned and adapted for grinding the plant diet.
2. Mesohippus: It was slightly taller than Eohippus. It had three toes in each foot.
3. Merychippus: It had a size of approximately 100 cm. Although it still had three toes in each foot, it could run on one toe. The side toe did not touch the ground. The molars were adapted for chewing the grass.
4. Pliohippus: It resembled the modern horse and was around 108 cm tall. It had a single functional toe with splints of 2^nd and 4^th in each limb.
5. Equus: Pliohippus gave rise to Equus or the modern horse, with one toe in each foot. They have incisors for cutting grass and molars for grinding food.