In the snail cepaea nemoralis, an autosomal allele causing a banded shell, u, is recessive to the allele for an unbanded shell, u. genes at a different locus determine the background color of the shell. the allele for a yellow shell, b, is recessive to the allele for a brown shell, b. a banded, yellow snail is crossed with a homozygous brown, unbanded snail. the f1 progeny are then crossed with banded, yellow snails in a testcross. predict the percentage of progeny in each phenotype if the two genes are linked with no recombination, if the two genes assort independently, and if the genes are 20 m. u. apart. place the percentage for each phenotype for each of the scenarios in the table below. percentages can be used more than once.

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.