Bio Midterm #1

The ability to taste phenylthiocarbamide (PTC) is a trait controlled by 2 alleles (PTC taster and PTC non-taster). Suppose 36% of a remote mountain village cannot taste PTC and must, therefore, be homozygous recessive (aa) for the PTC non-taster allele. If this population conforms to Hardy-Weinberg expectations for this gene, what percentage of the population must be heterozygous (Aa) for the PTC taster allele?

16% 48% ✅ 40% 32% 60%

Given a population that contains genetic variation, what is the correct sequence of the following events under the influence of natural selection? 1. Well-adapted individuals leave more offspring than do poorly adapted individuals. 2. A change occurs in the environment. 3. Genetic frequencies within the population change. 4. Poorly adapted individuals have decreased survivorship.

2 → 4 → 1 → 3 ✅ 4 → 2 → 1 → 3 4 → 1 → 2 → 3 4 → 2 → 3 → 1 2 → 4 → 3 → 1

If goats are crossed with sheep, embryos will form but cease development and spontaneously abort. This is an example of

A prezygotic mechanism Hybrid sterility Hybrid breakdown Spermatic behavior Hybrid inviability ✅

As a researcher you discover a genetic disorder in homozygous recessives that causes death during the teenage years. If 9 in 10,000 newborn babies have the disease, what are the expected frequencies of the dominant (A1) and recessive (A2) alleles according to the Hardy-Weinberg model?

A1 = 0.9997, A2 = 0.0003 A1 = 0.03, A2 = 0.9700 A1 = 0.0003, A2 = 0.9997 A1 = 0.9600, A2 = 0.0400 A1 = 0.9700, A2 = 0.0300 ✅

Dandelions, Taraxacum officinale, are plants that asexually produce fruitlike propagules. Sexual reproduction is very rare in this organism. Which species concept would be least useful in defining dandelions as a species?

Biological species concept ✅ Phylogenetic species concept Evolutionary species concept Ecological species concept Both the evolutionary and ecological species concepts

There is a population of beetles that typically have black wings. A scientist studying these beetles knows that their eggs hatch in early spring, the young insects grow through the late spring and summer, they lay eggs in the early fall, and they die in the early winter. Recently some beetles have been born with white wings. Early in life, the black- and white-winged beetles seem to be very similar in number of mating events, eggs laid, and survival rates, but shortly after laying their eggs the white beetles die and there are only black-winged beetles during the late fall. Which of the following is a true statement about the beetles?

Black-winged beetles have a higher fitness than white-winged beetles. The number of baby white-winged beetles will decrease in frequency over time. White- and black-winged beetles have equal fitness. ✅ White wings are an adaptation.

Which of the following is a fitness trade-off?

In some hornbill species, the male helps seal the female in a tree with her nest until the young are ready to leave the nest. Hummingbirds are the best pollinators of certain flowers, but bees are the best pollinators for orchids. The strong, thick beak of a woodpecker helps it find insects in trees. Turtle shells provide protection but are heavy and burdensome when moving. ✅

Why doesn't inbreeding depression, by itself, cause evolution?

It does not change the population's allele frequencies. ✅ It decreases the population's average fitness. It limits gene flow. It increases homozygosity. It violates the Hardy-Weinberg assumptions.

A confused frog deposits its sperm onto a toad's eggs as they are being laid. No offspring develop because the frog's sperm are unable to penetrate the toad's egg. This is an example of

Mechanical isolation Gametic isolation ✅ Temporal isolation Habitat isolation Behavioral isolation

How is a species defined according to the phylogenetic species concept?

Members of the same species share analogous traits. It is the smallest monophyletic group on the tree of life. ✅ It depends on the occurrence of reproductive isolation. All individuals that are the same size and shape would be considered the same species.

Evolution in a population of island iguanas can be caused by the following agent(s):

Natural selection Genetic drift Gene flow Both natural selection and genetic drift ✅ All of the above ✅

Over long periods of time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?

Natural selection accounts for these losses by the principle of use and disuse. Natural selection cannot account for losses, but accounts only for new structures and functions. Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits. ✅ The ancestors of these organisms experienced harmful mutations that forced them to lose these structures.

Which of the following statements best describes the rationale for applying the principle of parsimony in constructing phylogenetic trees?

Parsimony allows the researcher to "root" the tree. Similarity due to common ancestry should be more common than similarity due to convergent evolution. ✅ The molecular clock validates the principle of parsimony. The outgroup roots the tree, allowing the principle of parsimony to be applied.

Which of the following situations would be MOST likely to produce a new species?

Several individuals join an existing population and introduce several new, beneficial alleles. Several individuals colonize a new area and establish a population. Migration between the two populations is common. An existing species becomes subdivided by a glacier and the resulting groups remain physically isolated from each other for thousands of years. When the glacier melts, the two groups are able to interbreed. A group of polyploid individuals arises by an abnormal mitosis. The polyploids can only produce viable offspring by mating with each other. ✅ A volcano erupts and kills all of the frogs on an island, along with many other species. New frogs colonize the island and begin reproducing rapidly because there are no longer any frog predators.

Two researchers experimentally formed tetraploid frogs by fertilizing diploid eggs from Rana porosa with diploid sperm from Rana maculata. When they mated these tetraploid frogs with each other, most of the offspring that survived to maturity were tetraploid, with chromosome sets of both diploid parent species. Based on these results, if this type of tetraploid formed in the wild, what would be the result?

The two parent species would interbreed and fuse into one species. The two parent species would recognize each other as mates. The tetraploids would be selected against. The tetraploids would be reproductively isolated from both parent species. ✅

About thirteen different species of finches inhabit the Galápagos Islands today, all descendants of a common ancestor from the South American mainland that arrived a few million years ago. Genetically, there are four distinct lineages, but the thirteen species are currently classified among three genera. The first lineage to diverge from the ancestral lineage was the warbler finch (genus Certhidea). Next to diverge was the vegetarian finch (genus Camarhynchus), followed by five tree finch species (also in genus Camarhynchus) and six ground finch species (genus Geospiza). If the six ground finch species have evolved most recently, then which of these is the most logical prediction?

They should be limited to the six islands that most recently emerged from the sea. They should share fewer anatomical homologies with each other than they share with the tree finches. The chances of hybridization between two ground finch species should be less than the chances of hybridization between two tree finch species. Their genomes should be more similar to each other than are the genomes of the five tree finch species. ✅

There is an island in the middle of a large river that houses a large population of ants. Damming of the river causes the island to flood and only the highest points of the island are now above water. The ants cannot swim, so are now in multiple isolated populations. Which of the following best describes this event?

This situation represents isolation by dispersal. This situation represents a form of sympatric speciation. Only a rare development of polyploidy could lead to speciation in this case. Speciation will not occur in this case because of gene flow. This situation represents isolation by vicariance. ✅

The question(s) below refer to the following table, which compares the % sequence homology of four different parts (two introns and two exons) of a gene that is found in five different eukaryotic species. Each part is numbered to indicate its distance from the promoter (for example, Intron I is the one closest to the promoter). The data reported for species A were obtained by comparing DNA from one member of species A to another member of species A. Species Intron I Exon I Intron VI Exon V A 100% 100% 100% 100% B 98% 99% 82% 96% C 98% 99% 89% 96% D 99% 99% 92% 97% E 98% 99% 80% 94% Based on the data table above, and assuming that time advances vertically, which phylogenetic tree is the most likely depiction of the evolutionary relationships among these five species? answerable question reference

Tree A Tree B Tree C Tree D ✅

which of the following trees, if any, depicts the same relationship among species as the tree below? answerable question reference

Tree A Tree B ✅ Tree C none of the above

Aristotle believed all organisms could be arranged in order of increasing complexity in a sequential ladder of life.

True ✅ False

Evolution can be detected by noting deviation from the Hardy-Weinberg equilibrium of allele frequencies in the gene pool of a population.

True ✅ False

All living things evolve during their lifetime?

True ✅ False

Three populations of crickets look very similar, but the males have courtship songs that sound different. What function would this difference in song likely serve if the populations came in contact?

a temporal reproductive isolating mechanism a behavioral reproductive isolating mechanism ✅ a postzygotic isolating mechanism a gametic reproductive isolating mechanism

Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer or more than this have reduced fitness. Which of the following terms best describes this situation?

artificial selection directional selection stabilizing selection ✅ disruptive selection sexual selection

Which of the following is the best modern definition of evolution?

descent with modification ✅ change in the number of genes in a population over time survival of the fittest inheritance of acquired characters

The same basic internal organs (kidneys, stomach, heart, lungs) are found in frogs, birds, snakes, and rodents. This is primarily an example of _.

developmental homology genetic correlation inheritance of acquired characteristics structural homology ✅

What does the biological species concept use as the primary criterion for determining a species?

geographic isolation gene flow ✅ niche differences morphological similarity

After the drought of 1977, researchers hypothesized that on the Galápagos island Daphne Major, medium ground finches with large, deep beaks survived better than those with smaller beaks because they could more easily crack and eat the tough Tribulus cistoides fruits. A tourist company sets up reliable feeding stations with a variety of bird seeds (different types and sizes) so that tourists can get a better look at the finches. Which of these events is now most likely to occur to finch beaks on this island?

increased variation in beak size and shape over time ✅ evolution of yet larger, deeper beaks over time, until all birds have relatively large, deep beaks evolution of smaller, pointier beaks over time, until all birds have relatively small, pointy beaks no change in beak size and shape over time

Lamarck's theory of inheritance of acquired characteristics _.

is no longer a valid and accepted theory presumes that changes to your somatic cells are inheritable - ie. you could inherit sunburn is not supported by modern day knowledge of genetic inheritance all of the above ✅

Which of the following is the most predictable outcome of increased gene flow between two populations?

lower average fitness in both populations higher average fitness in both populations increased genetic difference between the two populations increased genetic drift decreased genetic difference between the two populations ✅

Each of the following has a good chance of influencing gene frequencies in small populations, but which one most consistently requires a small population as a precondition for its occurrence?

mutation nonrandom mating genetic drift ✅ natural selection gene flow

The two key factors responsible for speciation among populations are:

mutation and heterozygote disadvantage reproductive isolation and genetic divergence ✅ postzygotic isolation and morphological change mutation and genetic drift

Why did we examine the salamander diversity geographically (1-sentence max)? Why is this a great model for examining speciation (1-sentence max)?

no answer ‍♀️

For biologists studying a large flatworm population in the lab, which Hardy-Weinberg condition is most difficult to meet?

no selection no genetic drift no gene flow no mutation ✅ random mating

Vestigial traits and neutral changes in DNA sequences are good examples of _.

nonadaptive traits ✅ adaptation acclimation convergent traits developmental homology

Most causes of speciation are relatively slow, in that they may take many generations to see changes, with the exception of _.

reinforcement colonization natural selection polyploidy ✅

Cystic fibrosis is a genetic disorder in homozygous recessive (ff) humans that typically causes death in late childhood. Over time, we would expect the f allele frequency to _ for this trait.

remain the same increase decrease ✅ fluctuate this can't be predicted

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in gene frequencies, at many loci, from all other populations including their original homeland. Which of the following likely explains the genetic uniqueness of this population?

sexual selection and bottleneck effect population bottleneck and Hardy-Weinberg equilibrium heterozygote advantage and stabilizing selection mutation and natural selection founder effect and genetic drift ✅

When using a cladistic approach to systematics, which of the following is considered most important for classification?

shared ancestral characters homoplasic ancestral characters the number of homoplasies overall phenotypic similarity shared derived characters ✅

Similar gill pouches in embryos of a chick, human, and cat are an example of _.

structural homology genetic homology the inheritance of acquired characters developmental homology ✅

In a hypothetical situation, a certain species of flea feeds only on pronghorn antelopes. In the western United States, pronghorns antelopes and cattle often associate with one another in the same open rangeland. Some of these fleas develop a strong preference for cattle blood and mate only with other fleas that prefer cattle blood. The host mammal can be considered as the fleas' habitat. If this situation persists, and new species evolve, this would be an example of _.

sympatric speciation and habitat isolation ✅ sympatric speciation and temporal isolation allopatric speciation and habitat isolation allopatric speciation and gametic isolation

One study of Hawaiian fruit flies (Drosophila) shows that each island harbors several different species, all appearing to be related to a single Drosophila species found on the continent. Which model of speciation would be most likely expected in this case?

sympatric speciation by polyploidy sympatric speciation by disruptive selection allopatric speciation by vicariance allopatric speciation by dispersal ✅

Reinforcement is most likely to occur when _.

the environment is changing hybrids have lower fitness than either parent population ✅ prezygotic isolating mechanisms are in place gene flow is low

Some molecular data place the giant panda in the bear family (Ursidae) but place the lesser panda in the raccoon family (Procyonidae). If the molecular data best reflect the evolutionary history of these two groups, then the morphological similarities of these two species is most likely due to .

the inheritance of acquired characteristics sexual selection possession of homoplasic (convergent) traits ✅ inheritance of shared derived characters possession of shared ancestral characters

Darwin and Wallace's theory of evolution by natural selection was revolutionary because it _.

was the first theory to propose a mathematical model which can be used to predict evolutionary change. dismissed the idea that species are constant and emphasized the importance of variation and change in populations. ✅ proved that individuals acclimated to their environment over time. was the first time a biologist had proposed that genes can be inherited from generation to generation.

The biological concept of species applies only to breeding populations

which are sufficiently large to constitute a viable reproductive group which are sufficiently uniform to be recognized by observation in experimental conditions in nature ✅