The skin of a human develops from an embryonic layer known as the

a) endoderm
b) mesoderm
c) meristem
d) ectoderm

The “ecological footprint” left by a citizen of a developed nation is about four times larger than that left by a citizen of a developing nation. why is this the case?

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

How do the sperm cells get from the stigma to the ovules?