<span>Amino acids are the basic structural unit of all proteins. A 'free' amino acid (a single amino acid) always has:
an amino group -NH2,
a carboxyl group -COOH
a hydrogen -H
a chemical group or side chain -"R".
Since the amino acids (except glycine) have 4 different groups attached to the a-carbon, they are optically active stereoisomers (recall 23.101 Organic Chemistry) although only L-isomers are found in proteins.
At a neutral pH, both the amino and the carboxyl groups are ionised, giving what is termed the zwitterionic</span>
Answer:
Explanation:
Clastic sediments or sedimentary rocks are classified based on grain size, clast and cementing material (matrix) composition, and texture. ... An example of clastic environment would be a river system in which the full range of grains being transported by the moving water consist of pieces eroded from solid rock upstream.
Answer:
a. a portion of the population becomes isolated from the remainder of the population and experiences different selective pressures
Explanation:
This is an example of allopatric speciation Allopatric speciation is a form of speciation (formation of new species) that occurs as a result of geographic isolation. This means that a part of population becomes physically separated from the initial main population. There is no gene flow between these two populations and as a result the two populations reach a high level of genetic divergence. They can no longer interbreed which means they become two different species (speciation).
New populations evolve as result of mutation, genetic drift and natural selection.
For example, Galapagos finches are isolated from others by the ocean (geographic isolation). Because of the isolation, the finches don’t breed with one another. So, they developed unique characteristics and became endemic.