The red pigment in erythrocytes is whitch transports oxygen.
a. hemoglobin
b. phycoerythrin
c. carotenoid
d. chlorophyll

Select the correct answer. which term do biologists use to describe the average number of individuals of a species per unit area? a. carrying capacity b. population density c. minimal viable population d. survivability curve

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

What is the difference between a meteoroid and a meteor?