Answer:
Question 8. The correct answer is D: "<em>A butterfly population includes both green and yellow butterflies, and a predator sees yellow more easily than it does green"</em>.
Question 9. The correct answer is graph C.
Question 10. The correct answer is C: "<em>The fact that the bone structures are similar supports the theory that the animals shared a common ancestor</em>".
Explanation:
- <em><u>Question 8</u></em>:
Natural selection is the result of the phenotype-environment interaction which determines gene destiny in space and time, selecting beneficial alleles and increasing their frequency in the population. Natural selection can lead to speciation, driving to evolution. There are different types of natural selection: sexual selection, stabilizing selection, directional selection, frequency-dependent selection, and disruptive selection.
The exposed example: "<em>A butterfly population includes both green and yellow butterflies, and a predator sees yellow more easily than it does green</em>", is an example of directional selection.
Directional selection increases the proportion of individuals with an extreme phenotypic trait. In the example, natural selection will favor the green trait in butterflies over yellow, because as predators see better the yellow ones, these butterflies have more chances to be eaten. So the population must evolve to green traits to avoid predation.
Disruptive selection occurs when selective pressure favor homozygous. In equilibrium, the two alleles might be present or one of them might be lost. If an environment has extremes, then in these environments, both alleles are presented in homozygous.
The disruptive selection causes an increase in the two types of extreme phenotypes over the intermediate forms. Limits between one extreme and the other are frequently very sharped. Individuals belonging to one phenotype can not live in the same area as individuals belonging to the other phenotype, due to the traits differences between them, competition, predation, etcetera.
Both extreme phenotypes have been favored over intermediated forms. In this way, populations show two extreme phenotypes and a few individuals in the middle. Individuals who survive best are the ones who have traits on the extremes forms. Individuals in the middle are not successful at survival or reproduction.
Disruptive selection can lead to speciation, driving to evolution. This is why it is also called "diversifying selection".
The graph representing this selection must show two pics, spacially separated from each other, reflecting the two extreme phenotypes in the population.
- <u><em>Question 10</em></u>:
Classification of the biologic diversity intends to reflect the evolutive process that made a place to different organisms. This is estimating phylogeny, and it refers to the reconstruction of the evolutive ways that resulted in different groups. Estimating phylogeny can be based on characters, and these last ones might be morphological, physiological, cytological, among others.
Apomorphies and plesiomorphies are homologous characters shared by an ancestor and its derivated groups. Two characters are homologous if they share the same fundamental structure, if they share the same embryologic development, or if they share relation with adjacent structures. This is the case of the bone structures.
A bat wing, an alligator leg, a horse leg, a dolphin flipper, and a human arm are homologous structures. This is an ancestral homology, a character inherited from a common ancestor.
A common ancestor that is exposed to different pressures in different environments suffers changes in time as a result adaptation to the new environmental conditions. These changes lead to diversification and speciation.
The fact that the bone structures are similar supports the theory that the animals shared a common ancestor.
