When you are looking at this you can see that there are tiny rocks. The tiny rocks are the ones that are light brown and dark brown. But what are the black things floating around the river?

could be polution/trash

Explanation:

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.

the answer is: metamorphic rocks often show the presence of fossils, also a

hope i

-lavira: )