Answer: A semi-permeable membrane is that which only allows certain
substances to pass through.
<span>Mechanical waves....</span>
The barnacles are only able to attach them selfs to surfaces in the water. Since the surface is limited, barnacles are attaching themselves to the other barnacles, crowding the rock. The muscles were not able to grow or attach themselves off the surface of the rock. Same thing with the mussels that are growing on the rock. So not only barnacles are crowding the rock, but Mussels as well are crowding the rock.
<span>The three groups of amphibians: Frogs, Salamanders, Caecilians are different when they reach adulthood. Frogs have four legs with strong hind legs and no tails. Salamanders have tails and four short, weak legs that cause them to walk instead of jump. Lastly, Cacilians have no legs and are burrowing animals.
Amphibians must live in moist environments because they loose water through their thin skin. They need to be near water to replenish the lost water. Also their skin helps them breathe and they can get oxygen from the water.</span>
