15. Each of the following is a density-dependent limiting factor EXCEPT A. crowding
B. competition
C. disease
D. seasonal cycles

Environmental differences within ecosystems are generally caused by

The first amino acid of a new polypeptide chain is

What is it called when part of a cell membrane closes around a molecule to allow the molecule to enter the cell? a. passive transport b.diffusion c. endocytosis d. exocytosisc. endocytosis