Evidence unearthed by scientists supports the conclusion that about 65 million years ago a large object from space crashed into an area north of what is now the Yucatan Peninsula of Mexico. The impact threw huge amounts of dust into the atmosphere which spread across Earth's
sky, blocking the sunlight. At about the same time
dinosaurs, and many other forms of life in all regions of Earth, became extinct.
Describe how this event could have caused herbivorous and carnivorous organisms to become extinct.

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.

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human impact on the environment can be seen in the deterioration of the !

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not sure if this what   you'r looking for would be percent composition