Why are certain amino acids called essential amino acids? a. because they are available in abundance b. because they are not manufactured by the body c. because they can form bonds with any molecule d. because they are the most stable among all the amino acids e. because they are needed for the formation of all biomolecules?

Temperatures in ponds and lakes vary by season. select the best answer from the choices provided t f

The embryos of a bird, a reptile, and a mammal are similar in appearance. how does comparing the physical appearance of embryos of different species support the theory of evolution? a. it shows that these organisms share a common ancestor. b. it provides evidence that these organisms eat the same foods.c. it shows that these organisms share the same habitat.d. it provides evidence that these organisms suffered a genetic mutation.

All phases of matter may have a fixed mass