Without genetic variation, the mechanisms of evolutionary change will not occur. There are several sources of genetic variation within a breeding population: sexual reproduction, mutation, and gene flow. Specifically, sexual reproduction contributes to
genetic variation and as a result, evolution, through recombination. Describe recombination and analyze how it contributes to
genetic variability. Choose ALL that apply.

A, B, and D

Explanation: I just took the test

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.    

here is the answer

water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. weathering is the breaking down or dissolving of rocks and minerals on earths surface. once a rock has been broken down, a process called erosion transports the bits of rock and minerals away.