The system is a group of proteins in the blood that attack pathogens that enter the body and kill them.

The response is the basis for vaccination. primary secondary tertiary none of the above

Several bird species feed in a certain species of tree. each bird species feeds in a different part of the tree. which statement is true of these bird species? a. they have adapted to different niches due to competition b. they have a carnivorous relationship with the tree species. c. they have adapted to different niches due to predation d. they have a symbiotic relationship with the tree species.

When the cell concentrates potassium within, against the natural tendency of matter, it is performing a.passive diffusion b.facilitated diffusion c.active transport d.pinocytosis