What are the environmental pressures and variations of a shark

Shark Environmental Pressures. During their 400-million-year reign, sharks have faced environmental pressures similar to those confronting all species -- they must acquire food, escape predators, find mating partners and ensure the survival of their offspring.

Explanation:

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .