Evolution & Speciation Quiz

The correct answer is habitat isolation. Habitat isolation occurs when species live in different habitats and therefore do not come into contact with each other to reproduce. In this case, one species lives in tree holes and another species lives in streams, preventing them from interbreeding and maintaining their species boundaries.

The male satin bowerbirds' behavior of adorning their bowers with ornaments to attract females is a clear example of sexual selection. Sexual selection refers to the process by which certain traits or behaviors that increase an individual's reproductive success are favored and passed on to future generations. In this case, the male bowerbirds' elaborate displays and decorations are directly linked to their ability to attract mates and successfully reproduce. This behavior has evolved over time as a result of females choosing mates based on these elaborate displays, thus leading to the evolution of this male behavior.

Allopatric speciation refers to the formation of new species due to geographic isolation. When a population becomes physically separated by a geographic barrier such as a mountain range or a body of water, it can lead to the accumulation of genetic differences over time, eventually resulting in the formation of new species. In this process, reproductive isolation occurs, preventing gene flow between the separated populations. Therefore, geographic isolation is a defining characteristic of allopatric speciation.

Temporal isolation is the correct answer because the reproductive barriers in this scenario are based on differences in the timing of mating seasons. Each species mates during a specific window of time when the daylight is increasing by a specific duration. This temporal difference prevents the species from interbreeding and maintains their species boundaries.

This scenario represents behavioral isolation as a reproductive barrier. The singing behavior of the males is specific to their respective species and is influenced by the presence or absence of predators. This behavioral difference prevents interbreeding between the species, maintaining their species boundaries.

The elaborate courtship rituals and behaviors exhibited by males of different species of fruit flies in the same parts of the Hawaiian islands suggest that this represents behavioral isolation. This type of reproductive isolation occurs when individuals of different species have different courtship behaviors or rituals that prevent them from successfully mating with each other. In this case, the specific behaviors and movements performed by the males are unique to their own species and serve to attract females of the same species while deterring males from other species. This behavioral barrier prevents interbreeding between different species of fruit flies.

Directional selection is the best term to describe the gradual increase in size of horses over geologic time. Directional selection occurs when individuals with a particular trait that is advantageous in a specific environment have higher fitness and survival rates, leading to a shift in the population towards that trait. In this case, larger size may have provided horses with advantages such as increased speed or ability to defend against predators, resulting in the gradual increase in size over time.

The correct answer is mechanical isolation. This is because the reproductive barrier in this scenario is based on physical incompatibility between the males and females of different species. The males of one species are too small to physically engage in amplexus (mating position) with females of other species, preventing successful reproduction. This physical incompatibility acts as a barrier to gene flow between the species, maintaining their distinct identities.

A taxon, all of whose members have the same common ancestor, is monophyletic. This means that all the organisms in this taxon share a common ancestor and are descended from it. The monophyletic group includes all the descendants of the common ancestor, and it represents a single branch on the phylogenetic tree. This is in contrast to paraphyletic and polyphyletic groups, which do not include all the descendants of a common ancestor.

Stabilizing selection occurs when individuals with average traits have higher fitness compared to those with extreme traits. In this case, sparrows with average-sized wings are more likely to survive severe storms, suggesting that extreme wing lengths (either longer or shorter) are less advantageous. This selection process helps maintain the population's average wing size, leading to stabilizing selection.

If long-term climatic change resulted in all seeds becoming hard, the finch population would experience directional selection. This is because the selection pressure would favor the large-billed birds, which are specialized in cracking hard seeds. As a result, the population would gradually shift towards having a higher proportion of large-billed birds, as they would have a higher fitness advantage in the new environment. This would lead to a directional change in the trait distribution within the population.

In a Hardy-Weinberg population, the frequency of individuals with a certain genotype can be calculated using the equation p^2 + 2pq + q^2 = 1, where p and q represent the frequencies of the two alleles. In this case, the frequency of allele a is given as 0.2, so the frequency of allele A would be 0.8 (1 - 0.2). Using the equation, we can calculate the frequency of individuals with the Aa genotype as 2pq = 2(0.8)(0.2) = 0.32.

When we say that an individual organism has a greater fitness than another individual, it means that the organism is able to produce more viable offspring compared to others of its species. Fitness is a measure of an organism's ability to survive and reproduce in its environment, and leaving more viable offspring indicates a higher level of reproductive success. This means that the organism's genetic traits are being passed on to the next generation at a higher rate, leading to an increase in the overall fitness of the species.

The frequency of the B allele can be calculated by adding up the number of individuals with the BB genotype (360) and half the number of individuals with the AB genotype (480/2 = 240), which gives a total of 600 individuals with the B allele. To find the frequency, divide this number by the total number of individuals in the population (1,000), resulting in a frequency of 0.60.

The scenario described in the question is an example of sympatric speciation. Sympatric speciation occurs when two populations of a species diverge and become reproductively isolated from each other within the same geographic area. In this case, the original population of beetles preferred the orange flowers, while a variant of the beetles emerged that preferred the red flowers. Over time, these two beetle variants diverged to the point where they could no longer interbreed, leading to the formation of two separate species.

In a Hardy-Weinberg equilibrium, the frequency of heterozygotes can be calculated using the equation 2pq, where p is the frequency of allele A and q is the frequency of allele a. Since the frequency of allele a is given as 0.1, q = 0.1. The frequency of allele A can be calculated as 1 - q, which is 0.9. Plugging these values into the equation, we get 2 * 0.9 * 0.1 = 0.18. Multiplying by 100 gives us 18%, which represents the percentage of the population that is heterozygous for this allele.

In a Hardy-Weinberg population, the frequency of a specific allele can be calculated by squaring the frequency of the homozygous dominant genotype and adding it to twice the frequency of the heterozygous genotype. Since the population is in equilibrium, the frequency of the heterozygous genotype is 2pq, where p is the frequency of allele A and q is the frequency of allele a. Given that the frequency of allele a is 0.4, the frequency of allele A is 0.6 (1 - 0.4). Therefore, the frequency of the heterozygous genotype is 2(0.6)(0.4) = 0.48. Since the question asks for the percentage of the population that is homozygous for allele a, we subtract the frequency of the heterozygous genotype from 1, resulting in 1 - 0.48 = 0.52. Multiplying this by 100 gives us 52%, so the correct answer is 16%.

The mechanism for keeping the two frog species separate is hybrid inviability. This means that when the two species mate, the resulting offspring fail to develop and hatch, preventing the formation of viable hybrids.

The wings of a bird and those of an insect are least likely to be homologous because they have different evolutionary origins. Birds have wings made of feathers, while insects have wings made of chitin. Feathers and chitin are structurally and compositionally different, indicating that the wings of birds and insects have evolved independently and are not derived from a common ancestor. In contrast, the other options involve structures that are more likely to be homologous, as they are found in closely related species or have similar functions in different species.

A polyphyletic grouping is a taxonomic group that includes species from different ancestral lineages. In this case, species R, S, Y, and Z do not share a common ancestor with each other, as they have different ancestors (U and V). Therefore, grouping them together is considered polyphyletic.

The correct answer is B and C only. This is because the dorsal fins and tails of ichthyosaurs and fish are examples of convergent evolution, where similar traits evolve independently in unrelated species due to similar selective pressures in their environment. Additionally, these traits can also be considered adaptations to a common environment, as both ichthyosaurs and fish lived in aquatic environments and needed these structures for efficient swimming.

Natural selection is the process by which individuals with traits that are better suited to their environment have a higher chance of survival and reproduction, passing on their advantageous traits to future generations. This process is driven by several factors, including genetic variation within populations, the differential reproductive success of individuals, the high mortality rate of offspring, and the overproduction of individuals compared to available resources. However, the statement that individuals adapt to their environments and, thereby, evolve is incorrect because natural selection acts on individuals with preexisting traits, rather than individuals actively adapting and evolving in response to their environment.

When there is an imbalance in the sex ratio of a species, the members of the minority sex receive a greater proportion of care and resources from parents. This suggests that the fitness of the offspring is dependent on the frequency of their sex in the population. If the minority sex is favored and receives more resources, it will have a higher chance of survival and reproduction, leading to an increase in its frequency. This is an example of frequency-dependent selection, where the fitness of a phenotype depends on its frequency in the population.

In Hardy-Weinberg equilibrium, the frequency of the dominant allele (p) plus the frequency of the recessive allele (q) equals 1. We are given that there are 36 purple-flowering plants (genotype RR) and 64 white-flowering plants (genotype rr) in the population. Since the purple-flowering plants (RR) represent the frequency of the dominant allele (p^2), we can calculate p as the square root of 36/100, which is 0.6. Therefore, q would be 1 - p, which is 1 - 0.6, equal to 0.4. However, since the question asks for the value of q, we need to take the square root of q, which is 0.4, resulting in 0.8. Hence, the correct answer is 0.80.

A trend toward the decrease in the size of plants on the slopes of mountains as altitudes increase is an example of a cline. A cline refers to a gradual change in a trait or characteristic of a population along a geographic gradient. In this case, as the altitude increases, the size of plants decreases, indicating a gradual change in plant size along the mountain slope. This pattern suggests that the environmental conditions and selective pressures vary with altitude, leading to the observed variation in plant size.

Diploidy refers to the presence of two copies of each gene in an individual. In the case of the recessive allele that causes phenylketonuria (PKU), individuals who are heterozygous (having one copy of the harmful allele and one copy of the normal allele) do not exhibit the harmful effects of PKU. This is because the normal allele can mask the effects of the harmful allele. Therefore, individuals carrying one copy of the harmful allele can still survive and reproduce, maintaining the presence of the harmful allele in the population's gene pool.