Week 3: Analogy/Homology

1) Homologous trait: Echolocation in regard to sperm and killer whales
A) The two species that possess echolocation are sperm whales and killer whales, which are both Odontocetes, or toothed whales. Both whales' habitats are distributed throughout all oceans.
B) In all Odontocetes, echolocation is achieved through the passing of air through the phonic lips, which create clicks in the direction the whale's head is facing. The sounds themselves are focused in a whale's melon, which is part of the nasal apparatus. The sounds, or clicks, are then bounced back and heard within the whale's inner ear. In regard to killer whales, echolocation is used for both hunting and communication. Because killer whales do not hunt in excessively deep waters, the wavelengths used for creating their clicks are not very low and their range of hearing in regard to echolocation matches the sounds they produce. In regard to sperm whales, because they hunt under the photic zone (where light can penetrate), they use much lower frequencies when echolocating.
C) The common ancestor of these two species was a toothed whale that had developed echolocation. This is known because all Odontocetes possess echolocation, which is attributed to a common ancestor who had evolved this trait for hunting.
D)

2) Analogous trait: Echolocation in killer whales and microbats

A) The marine mammals known as killer whales, which possess the trait of echolocation, are Odontocetes. Microbats are a suborder within bats, which are flying mammals, and are known for their ability to use echolocation. The Australian ghost bat, which is carnivorous and hunts large insects, lizards, frogs, birds, and other bats is the particular microbat that I will focus on.

B) Both killer whales and Australian ghost bats use echolocation as a hunting tool. In Australian ghost bats, they emit high pitched sounds through using their vocal chords and once the sound has bounced off an object, it returns and is heard through the bat's ears. The bat is able to identify how big the object is by the intensity of the echo and it's direction by which ear the sound returned to. The killer whale produces a click through the passing of air through it's phonic lips and picks up the sound once it bounces back through it's inner ear. Killer whales also use forms of these clicks to communicate over long distances.

C) Both species are mammals, but whales are marine mammals while bats are flying, land-based mammals. The common ancestor to both species was indeed a mammal, but the common ancestor is so far back in both species' histories that it was before the development of echolocation. Therefore, echolocation is a case of parallel evolution.

D)