Why is bulk flow a necessary condition of complex multicellularity?
a. Organisms exhibiting complex multicellularity are large and have cells/tissues that are not in contact with their environment.
b. Systems that can overcome the limits of diffusion must evolve for basic physiologic processes to occur.
c. Complex multicellularity is related to the increase in oxygen in the environment.
d. Because bulk flow systems are only related to the delivery of oxygen to tissues, higher environmental oxygen selected for individuals with bulk flow systems.
e. Bulk flow is necessary to move large amounts of liquid through the organism, depending on physiologic needs.
f. The tissues can all receive necessary nutrients from the environment, but bulk flow speeds the rate of diffusion.
g. Complex multicellularity reflects cell adhesion between cells, and this cannot happen without bulk flow of signaling molecules from the environment.