Organisms can be classified in the same species by morphology and

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

because they are eaten by the frog and the frog getseaten by the snake and the snake by the eagle

not sure if this is what you'r looking for nnew= nold

answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;