11 Biology By BISM Academy
15 – Transportation in animals
TRANSPORT IN ANIMALS
Unicellular animals have maximum surface area to volume ratio; and most of the substances move into or out of their bodies by simple diffusion, osmosis, active transport, and facilitated diffusion. So there are no special transport systems involved.
Simple multicellular.
Same is true of simple multicellular animals which are aquatic. Complex multicellular. But complex multicellular animals possess highly organized, and well developed transport system, in the form of blood vascular system. TRANSPORTATION IN HYDRA. It is fresh water in habitat.
Body structure.
The body is two layered; the outer ectoderm and inner endoderm; in between them is mesogloea which is non-cellular. The outer surfaces of the ectoderm cells are exposed to the water in which the animal lives.
Intake of material.
Water, dissolved 02 , and food are taken into the coelenteron (enteron) of Hydra by the movement of tentacles, and flagella which are present in most cells of endoderm.