High-flying birds are able to obtain enough oxygen even when the air is very thin because

What type of appendages do sponges cnidarians roundworms annelids mollusks arthropods echinoderms and vertebrate have? jointed, not jointed, absent  

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

No plagiarizing ! 6th grade work! easy and 100 compare the parts of a cell and the cell as a whole to another common nonliving system (i.e., a car, a city, describe the parts of a cell and their primary function.