The answer is whales. In the Antartic and Arctic regions, krills and whales are very abundant in numbers. Whales are number one consumer of krills in these regions. They can feed on a large swarm of krills when they feed. They also have less competition on these icy waters. They gain energy every time from eating them.
Sorry if I’m wrong but I believe it’s the cardiovascular and lymphatic system
Hope this helps!
Wind energy because it's natural and some places dont have electricity.
