Today, many types of organisms live in a marine environment. when did most of the phyla of marine animals alive today first appear?

a. proterozoic
b. cretaceous
c. cambrian
d. permian

Option C, Cambriam

Explanation:

During the Cambrian period explosion of life has taken place. This period started about 543 million years ago and most of invertebrate form of life evolved during this phase among which the trilobites were the abundant ones. More than 100 types of trilobites were found during those times.  

Some of the common aquatic species that evolved during those times and are existing till today include mollusks, worms, echinoderms , sponges, chordates, algae etc.  

Hence, option C is correct

from my research i have to the conclusion that decomposers, such as fungi, bacteria and invertebrates, play a critical role in nutrient cycling and without them the earth's ecosystem may not support life as we know it. elements such as carbon, nitrogen and phosphorus exist in limited amounts on earth, although huge amounts of carbon are being released into the atmosphere from underground sources now by humans. it is still extremely important that other nutrients be retained by the process of re-use. decomposers are organisms that are able to chemically break down dead material and make these elements available for use by other organisms. without this breakdown of dead material, dead bodies would pile up. so decomposers also play a role in clean up also. without them, life might not continue as we know it and dead material would overwhelm the earth.    

what in the weirdo : o