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

(N/A) 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 evolutionary sequence is as follows:
$(i)$ $Eohippus$ (Eocene period): It had a short head and neck. It had four functional toes on each forelimb and three on each hind limb. The molars were short-crowned,adapted for grinding soft plant material.
$(ii)$ $Mesohippus$ (Oligocene period): It was slightly taller than $Eohippus$. It had three toes in each foot.
$(iii)$ $Merychippus$ (Miocene period): It was approximately $100 \ cm$ tall. Although it still had three toes in each foot,it could run on one central toe. The side toes did not touch the ground. The molars were adapted for chewing grass.
$(iv)$ $Pliohippus$ (Pliocene period): It resembled the modern horse and was around $108 \ cm$ tall. It had a single functional toe with splints of the $2^{nd}$ and $4^{th}$ digits in each limb.
$(v)$ $Equus$ (Pleistocene period): $Pliohippus$ gave rise to $Equus$,the modern horse,with one functional toe in each foot. They have incisors for cutting grass and complex molars for grinding food.