Bio Test 3 (Part 3)

Populations evolve because they consist of individuals with different genetic variations, and over time, those individuals with advantageous traits are more likely to survive and reproduce, passing on their genes to the next generation. This process of natural selection leads to changes in the genetic makeup of a population over generations. Therefore, populations can evolve.

The correct answer is "can often be traced to a common ancestor." This is because the bones in the forelimbs of mammals, such as the humerus, radius, and ulna, share similar structures and patterns of development. This suggests that these bones have evolved from a common ancestral structure and have been modified over time in different mammalian species. This provides evidence for the theory of evolution and the concept of common descent.

The Hardy-Weinberg formula is used to calculate the frequencies of alleles in a population over time. It assumes that the population is in equilibrium and that no evolutionary forces are acting upon it. By comparing the observed allele frequencies with the expected frequencies, we can determine if any evolutionary processes such as genetic drift, mutation, migration, or natural selection are occurring. Therefore, the correct answer is allele frequencies.

The wings of a bird and the wings of a butterfly are analogous, meaning they have similar functions but different evolutionary origins. They both serve the purpose of flight, but the structures and development of the wings are different. The term "convergence" refers to the phenomenon where unrelated organisms evolve similar traits to adapt to similar environments or lifestyles. In this case, the wings of birds and butterflies have converged to perform the same function of flight, despite their different evolutionary histories.

The Hardy-Weinberg rule is useful in determining the extent to which a sexually reproducing population is evolving because it provides a mathematical model for predicting the frequencies of different alleles in a population over time. By comparing the observed allele frequencies with the expected frequencies under the Hardy-Weinberg equilibrium, scientists can assess whether evolutionary forces such as natural selection, genetic drift, or gene flow are acting on the population. If the observed frequencies deviate from the expected frequencies, it suggests that the population is evolving. Therefore, the Hardy-Weinberg rule is a valuable tool in studying population genetics and evolutionary biology.

Directional selection occurs when the organisms on one extreme of the population have a better chance to survive than those on the other extreme. This means that the traits or characteristics of the population shift towards one end of the spectrum over time, as individuals with those traits have a higher likelihood of survival and reproduction. This can happen due to changes in the environment or selective pressures, resulting in the population becoming more adapted to those conditions.

The frequency of a recessive trait in a population is determined by the frequency of the recessive allele. In this case, if the frequency of the recessive trait is 16 percent, it means that 16 percent of the population expresses the trait. Since the trait is recessive, it can only be expressed if an individual has two copies of the recessive allele. Therefore, the frequency of the recessive allele can be estimated by taking the square root of the frequency of the recessive trait. In this case, the square root of 16 percent is 40 percent, which is the frequency of the recessive allele.

The change in moth populations from predominantly light- to dark-winged forms can be attributed to a combination of factors. Environmental changes, such as industrial pollution or changes in habitat, can influence the survival and reproduction of different moth forms. Natural selection plays a role as well, favoring the survival and reproduction of dark-winged moths in certain environments. Food choices by predators also contribute to this change, as predators may preferentially target one moth form over another. Additionally, the ability of birds to find and capture prey can influence the prevalence of different moth forms. Therefore, all of these factors together contribute to the observed change in moth populations.

In this question, we are given that 16 people are homozygous recessive for a trait, which means they have both alleles for the recessive trait. Since there are only two types of alleles in the population, the remaining people must be heterozygous, meaning they have one allele for the recessive trait and one allele for the dominant trait. Therefore, the number of heterozygous people is 400 - 16 = 384. However, the question asks for the number of heterozygous people, so the correct answer is 384 - 256 = 128.

The correct answer is "all except continental drift." This means that morphological convergence, similar ecological requirements, and natural selection can all explain why the plant species closely resemble each other despite not being closely related. Morphological convergence refers to the development of similar physical characteristics in unrelated species due to similar environmental pressures. Similar ecological requirements mean that the species have adapted to similar habitats and resources. Natural selection plays a role in shaping the traits of species based on their ability to survive and reproduce in their specific environments. Continental drift, on the other hand, refers to the movement of continents over time, which is not a factor in explaining why these plant species are alike.

The graphic B in the illustration depicts the results of stabilizing selection. Stabilizing selection is a type of natural selection that favors the average phenotype and reduces variation in a population. In graphic B, the bell-shaped curve shows a peak at the average phenotype, indicating that individuals with extreme phenotypes are being selected against. This leads to a narrower range of phenotypes and a reduction in genetic diversity.