i think it is maybe (A) maybe..
<span>The ischemic penumbra can maintain metabolic demand with marginal blood flow from collateral circulation for a maximum of 50% before increasing in size. A penumbra is the area where the flow of blood at about 25 - 50% can maintain normal metabolic demands for 6 - 8 hours only. When it continues to increase, the human cells will die and other neurological activity will be suspended causing the person to die slowly.</span>
Answer:
<u>C) They may provide selective advantages.
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<u>D) Slight differences in the genetic code may have significant results.</u>
Explanation:
The genetic code is universal, and present in most living beings . Generally, in most living organisms, the same codons are assigned to the same amino acids.
DNA sequences make up genes that may have multiple variants, called alleles. DNA deoxyribonucleic acid, is transcribed into mRNA and then translated into amino acids that form proteins.
Natural selection mainly acts on phenotypes, which are dependent on proteins and the organisms's environment. Phenotypes conferring advantageous traits are favored by the selection process- these help groups of organisms evolve over time.
The answer is A, a cell wall
B. By using up less calories than you take