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Flashcards in Equine Evolution Deck (15)
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Evolution is the process of change or modification in gene frequency over time. Different species evolve from a common ancestor. This process is never linear.


Define a GENUS

A genus means they are descended from the same family type.


Define a SPECIES

A species is a group of organisms that can breed and produce fertile offspring.


Who was Carolus Linnaeus?

An 18th century botanist. He documented precise descriptions of nature and divided organisms according to their genus or species.



Taxonomy is the practice and science of classification.


Why does evolution occur?

Due to environmental pressures - evolution is not a conscious decision. Genetic mutations occur regularly and randomly which may or may not help the animal survive these environmental pressures. These changes may be physiological or psychological. If an animal does not evolve well, it dies.


What are the two theories of evolution?

1. Lamarck's theory of acquired traits - changes in the environment causes changes in the needs of the animals living in that environment. These traits are inherited.
2. Darwin's theory of natural selection - random genetic mutations occur, of which beneficial ones are preserved because they aid survival.


What is the evolution of equus?

Hyracotherium, orohippus, mesohippus, miohippus, meryhippus, pliohippus.


Describe hyracotherium

Developed during the change of the climate as there was more grass available. 0.4m tall with a curved spine and small head. Had 4 toes in front and 3 toes behind. Ate mostly shoots and berries.


Describe orohippus

0.5m tall with a slim body and elongated head, slim forelimbs and long hindlimbs. Most likely a browser eater.


Describe mesohippus

0.6m tall. Had 3 toes in front and 3 behind. Spent a lot of time in open grassland, similar to the modern day horse.


Describe miohippus

0.8m tall. Ate grass and had a straighter spine and ridged teeth for grinding on grass. At this point the toes were reducing into one central toe.


Describe merychippus

1m tall with ridged teeth that allow grazing on forage throughout their life. The radius and ulna fused, making them faster than their ancestors. Size of jaw increased to house larger teeth.


Describe pliohippus

1.25m tall with eyes now on the side of the head. Side toes regressed metatarsals.


What is equus caballus?

The modern day horse is the only surviving genus. It has a long head, laterally placed eyes, and a keen sense of hearing. Has long limbs loaded over a central digit with a fight or flight response.