All of the following are limitations of the biological species concept, except for
it doesn't apply to asexual species.
it can't be applied to fossils.
it has trouble explaining hybrids, like wolf-dogs and grolar bears.
reasonably separating most species we see in day to day life..

It can't be applied to fossils

Explanation:

It's because fossils aren't living organisms.

the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation:

the answer is false?