What is a possible cause for a decrease in ecosystem productivity? a an increase in the biodiversiy of the ecosystem b a decrease of the biodiversity of an ecosystem c the biodiversity of an ecosystem experiencing no change d an ecosystem becoming more stable

The answer you're looking for is B. a decrease of the biodiversity of an ecosystem. The less biodiversity an ecosystem has, the less likely it is to increase, and more likely it is to decrease. This is because with less genetic variations, predators would either be able to find and kill prey with more ease, or with more difficulty, but there would over all be a lack of balance. This imbalance would cause for either predators to over populate until their food sources run out through over hunting, therefore killing the predators, or for the prey to over populate, kill the vegetation, therefore killing themselves, and then killing the predators that feed on the prey.

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.

if you look up in the top right corner you'll see your current profile picture, click than click "view profile" you'll be able to change it there.