The tricuspid valve shuts. This prevents blood from flowing backward into the right atrium while the ventricle contracts. So, your answer will be the Tricuslid Valve. Hope I helped!
Natural selection act directly upon <u>Alleles</u>
Explanation:
Genes, such as that of fur color, have many variants called alleles. Natural selection act on the alleles and chooses the best fit for an environment and eliminates the disadvantageous ones from the population over generations. Mutations are a rare occurrence that increases the number of allelic variants of a genes on which natural selection can act upon.
The answer would be -- A. Cenozoic
My guess:
I do not know the options to the blanks, but I'd say that the answer to the first one is "strongly linked". Think of a chromosome as a phylogenic chart → 2 species that are beside each other are strongly linked, if compared to 2 species 3 spots apart form each other. So, 2 genes that are close to each other are strongly linked.
I do not know the options to the blanks, but I'd say the answer to the second one is epistasis → which is the interaction between two different genes (different means they're not linked alleles).
Hope it helped,
BioTeacher101
