Question 6

a cork is able to float on water because it is

1)a crystalline solid

2)equal in density to water

3)small in size

4)less dense than the water

The cork has 4) Less dense than water.

The ability of the object either to float or sink on water depends on its density. If the mass of the object is heavy it sinks, whereas if it is light it floats on the surface. This is due to force of buoyancy.

Anything that buoys on water has more lightness than water, by definition. Various things influence lightness, yet one of these things is air content. Wood and plug skim for a similar explanation that life coats and Styrofoam drift: these materials have a ton of air in them, which makes them amazingly light.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.