A couple of questions about Marine animals...?

Question

1. Is it true that all mammals have their fins (or feet) move in an up and down motion? (like how whales and dolphins move their back fin up and down to move unlike the shark who moves it side to side...also humans move their feet up and down to swim especially in a swimming event i.e. the butterfly stroke).

2. Is it true that the orca or the killer whale got its name because when the spanish saw them they called them whale killer but it was translated wrong as killer whale. (I just found out the other day killer whales are dolphins...where have I been? lol)

Thanks a bunch! ♥

Answer 1

Question 1: Consider how your spine is built. You can flex pretty far forward and backward, but not too much from side-to-side. All mammals have similar spines in this regard, so mammals that evolved tailfins move them up and down because this plane has much greater flexibility than than a horizontal plane. Same thing with rear legs- the typical mammal skeleton would need major modifications for legs to work in a horizontal plane. The forefins of marine mammals can rotate to varying degrees, similar to a human shoulder.

Question 2: The name probably comes from French 'orque' a sea monster, named after Latin 'orca', meaning whale. The earliest written reference comes from Roman times, around 70 AD, where the whales were referred to as 'monsters' because they had sharp teeth and the ability to rip their prey to shreds.

Answer 2

1- Generally for swimming they do use an up and down movement but for slow swimming you'll see pinnipeds (seals and sea lions) along with mustilids (otters and sea otters) vary between side to side and up and down. Keep in mind that whales and dolphins are not the only aquatic mammals.

Answer 3

Seals and sealions use different methods of propulsion. Seals use the back flippers mainly in a side to side motion. The fore flippers are for steering. Sealions and fur seals use the fore flippers for propulsion and the rear flippers for steering. In whales and sea cows the rear flippers have fused into a horizontal fluke which can only provide propulsion with a vertical motion.