1. How is Earth's atmosphere like an ocean? How is it unlike an ocean?
2. Why do you think planes don't fly high in the stratosphere?

Answer 1: : how is earth's atmosphere like and unlike an ocean? Some similarities: they both contain water: ocean in a liquid form and atmosphere as water vapor and oxygen, although oceans have relatively little oxygen (but enough for the fish to catch).

Answer 2 :That trend of rising temperatures with altitude means that air in the stratosphere lacks the turbulence and updrafts of the troposphere beneath. Commercial passenger jets mostly fly in the lower stratosphere, partly because this less-turbulent layer provides a smoother ride.

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.