Using evolutionary principles, explain why large ears might be expected to evolve in a terrestrial plant eater such as a rabbit or deer but not in an aquatic mammal such as a seal.

Adv.

Answer:

It is given that the terrestrial plant eater such as rabbit or deer has large ears, where as aquatic mammals such as seals have very small ears. It can be said that the large ear of terrestrial plant eater is due to evolution. Also, due to the same evolution, aquatic mammals such as seals do not have large ears.

The large ears in terrestrial plant eater are one of the favourable features, which help them to survive and reproduce. Majority of these animals can twist their ears in the direction of the incoming sound. Other sense organs, such as eyes, touch and smell are helpful only within short distances. Ear, on other hand, can detect sound even from long distances. As these terrestrial plant eaters are always in a constant threat due to attack by predators, the big ears help them to detect even minute sounds of their approaching enemies.

The presence of big ears in terrestrial plant eaters helps them to detect the sound produced by other female or male organism and thereby, help in reproduction. Apart from this, the big ears of some terrestrial animals help to lose excess heat from the body. The big ears of these animals also help in balancing the body. Also, organisms, which have big ears, have improved sense of hearing. So, it is clear that the presence of big ear in terrestrial plant eaters serves as a favourable character in evolution.

Aquatic mammals such as seals do not have large ears because the body of aquatic animals are stream lined. It would be difficult for them to swim with big ears. As they are already in cold environment, the need for regulation of temperature by the ear does not arise. These animals have only inner ear; however, the lateral line system also helps in detection of stimulus. Due to the above reasons, big ear is not a favourable character in aquatic mammals such as seals.

Thus, the characters, which are favourable, pass to the subsequent generations, which happened in the case of terrestrial plant eaters, mentioned here. As big ears are not needed in aquatic mammals, they have only small ears.

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