To what does "descent with modification" refer? a. All species come from preexisting species and are changed over time.
b. All species come from preexisting species but stay basically the same.
c. Some species come from preexisting species and are changed over time.
d. Some species come from preexisting species but stay basically the same.

Which statement best describes a keystone species? o a. it has littlelmenetic variation. it has an extremely high population. 0 b. 0 c. it remains unaffected by all environmental changes. od. it has a strong influence on the ecosystem. 0 e. it's the first species to populate a new ecosystem.

You have just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals. what is the significance of this finding? it will be important to include cysteine in the diet of the mice. cysteine residues are required for the formation of α helices and β pleated sheets. cysteine residues are involved in disulfide bridges that form tertiary structure. cysteine causes bends, or angles, to occur in the tertiary structure of proteins.

Describe the impact of deforestation of both abiotic and biotic factors within the tropical rainforest.