Humans have both molar teeth (for chewing) and incisors (for biting) - why?

Camels have tough, hairy, rubbery lips. Why?

Asian elephants have molars which glue together to form one large tooth. They produce six sets of molar teeth throughout their lifetime. These teeth grow in from the back of the jaw - why?

This grass-eating baboon can curl back it's gums to show it's terrifying fangs. Why?

A goose has tooth-like bits on it's tongue. Why?

On average, sharks have 15 rows of teeth in each jaw. Why?

Hawks have hook-like beaks. Why?

Some snakes can unhinge their jaws. Why?

Hummingbirds can have very long, thin beaks. Why?

Mosquitos have long, hollow needle-like mouth parts. Why?

Pelicans have large pouch-like beaks. Why?

The teeth of a beaver never stop growing. Why?

The leatherback turtle's mouth is full of papillae. Why?