Biol 206 Evolutionary Genetics For Assessment Answer

Answer

Evolution of Horses

Part 1: timeline evolution of horses over the past 54 million ears from Hyracotherium to Equus.

 

Horse	Traits and changes
Hyracotherium	Hyracotherium horse lived in forest and was looking like a dog. Its The legs had four toes on every front foot, however, the hind feet had three toes. This horse made use of pads while walking. It had three incisors and the teeth being lowly crowned. It had one canine, different four premolars and three molars for grinding in every jaw according to Collins, 11179.
Orohippus	This horse was as a result of gradual change of Hyracotherium. It was still looking like a dog with legs short, neck short and its back was arched. Its toes were similar with Hyracotherium with three toes behind while four toes on front. It was still having the pad footed. However, there was distortion of first and second toes. The teeth undergone some changes the premolar on the behind transformed into molar.
Epihippus	This generation was still having pad foot. It looked like a dog. It had three toes behind while four toes occupied the front. It experienced evolution on the teeth. The last two premolars transformed to molars.
Mesohippus	Librado, 430 says that, Mesohippus horse seemed to be large than the earlier generation. It had evolved and not looking like a dog. The legs became longer together with the neck.  Both the hind feet and the front feet had 3 toes. The tooth transformed and could feed effectively.
Pliohippus	This horse undergone some changes on the toes. It had curved teeth unlike the other generation.
Equus	Equus had long neck, legs seemed to be long, as well as the nose its jaws seemed to be deep. It was looking like a horse not dog like. The toes were fully transformed. The horse was now living outside the forest and the long limbs could allow it to run and escape enemy.

Arabian horse character traits

Arabian horse came from the desert. The character traits that have made Arabian horse to be bred by human include; it has very strong hooves that can walk in the desert while carrying luggage, the strong hooves allow the horse to pass through the stones and sand in the desert. It feeds on less amount of food as compared to other types of horses according to Shoemaker, 220. Its tails are always high when in motion and the skin seems to be thin, this makes it to lose little amount of water and effective cooling of the body. While other breads of horse have fast-twitch muscles, this breed have slow-twitch muscles. The trait enables the horse to withstand in limited oxygen areas and walk longer distance. However, these character traits may change. Amount of food this horse feeds on may increase. Apart from that, the traits of the hooves would change because human travel with this horse in areas that is not desert.

Part 3

In this part, the area where the Arabian horse got lost is area where there is cool and wet climate. The changes that this horse would undergo is the trait of the hooves. The hooves would now grow thin as compared to the large hooves used to adapt on sand in reference to Semprebon,115. This place I muddy and thin hooves would now survive. The skin would develop thick hair to adapt on the cold that is in the area. The other inevitable change that the horse would undergo is the traits of the teeth. The teeth would grow smaller to feed on grass only as compared to the last time it was feeding on hard desert food.

Part 4

Before

                                         Figure 1: Arabian horse before getting lost in cool and wet climate (Librado, et al.2016: pp.430).

                                                                                       After staying in cold areas

                                                                              The toes have become sharp and body becoming hairy.

Work cited

Collins, Patrick J., et al. "Recent evolution of equine influenza and the origin of canine influenza." Proceedings of the National Academy of Sciences 111.30 (2014): 11175-11180.

Librado, Pablo, et al. "The evolutionary origin and genetic makeup of domestic horses." Genetics 204.2 (2016): 423-434.

Semprebon, Gina M., et al. "Paleodietary reconstruction of fossil horses from the Eocene through Pleistocene of North America." Palaeogeography, Palaeoclimatology, Palaeoecology 442 (2016): 110-127.

Shoemaker, Lauren, and Aaron Clauset. "Body mass evolution and diversification within horses (family Equidae)." Ecology letters 17.2 (2014): 211-220.