exam 4

What percentage of DNA sequences do all humans share?

>99%

Why is gene transfer among bacteria significant to human health?

A gene carrying antibiotic resistance can be transferred among bacteria, decreasing the likelihood that the antibiotic is effective in treating certain diseases.

Select the scenario in which a mutation may become fixed in a population.

A mutation occurs in a population of brown toads, causing green stripes that allow for better camouflaging in its habitat

Why do African populations have more genetic diversity than populations elsewhere in the world?

African populations are older than other populations and have had more time to accumulate mutations.

Select the statement that describes how fitness and natural selection interact to lead to adaptation.

Alleles well-suited to the environment increase the fitness of organisms, allowing for higher survival and reproduction so that the beneficial alleles are passed on to future generations and increase in incidence in the population over time.

Antibiotic-resistant strains of bacteria tend to first be found in hospitals. Which factor explains why this is the case?

Antibiotics are more likely to be present in hospitals, thus selecting for resistant strains.

What evidence exists that humans evolved in Africa? Select the TWO answers that are correct.

As shown by mtDNA studies, one branch of the human family tree consists of modern Africans, and the other branch consists of all other populations in the world. The oldest known fossils of modern humans, approximately 160,000 and 195,000 years old, were found in Ethiopia.

How is mtDNA used to trace lineages?

Differences in mtDNA can be used to group people into lineages and determine how long ago they shared a common ancestor.

Why are X-linked traits more commonly expressed in males than in females? Select the TWO answers that are correct.

Females have two X chromosomes, so one can mask the effects of the other. Males have only one X chromosome, whereas females have two.

What is meant by incomplete dominance?

Heterozygotes have a phenotype that is a mixture of the two alleles.

Select the scenarios that describe negative selection. Select the TWO answers that are correct.

In a population of a beetle species is an allele resulting in mouthparts that are not effective for chewing food. An allele leading to the development of a life-shortening condition is present in the human population.

Select the statement that correctly describes why human populations that moved north out of Africa developed lighter skin.

In the low-level UV light of the north, vitamin D production is insufficient with darker skin, and folate is not destroyed by the low levels of UV light, even with lighter skin.

What happens to the parent cell during binary fission?

It elongates, replicates its DNA, and divides in two.

How is mitochondrial DNA different than the DNA found in the nucleus of cells?

It is a circular piece of DNA that is inherited from the mother only.

Which statement is true about Y chromosome analysis?

It is commonly used to determine paternity and ancestry.

A bacterial cell that is resistant to a particular antibiotic may spend a large amount of energy producing the modified proteins that are needed for resistance. In such a case, what would be the effect on this cell's fitness if no antibiotic was present?

Its fitness would be lower than other strains that lack resistance because it is spending energy that the resistant strains can use for other purposes, such as reproduction.

What changes can humans make that can reduce their impact on the amount of carbon dioxide in the atmosphere? Select the TWO answers that are correct.

Limit the use of gasoline for transportation by using more fuel-efficient vehicles, carpools, and public transportation. Conserve electricity and rely more on power sources with less carbon impact, such as solar and wind energy

Why are more males than females affected by X-linked recessive genetic diseases?

Males have a Y chromosome that cannot mask the X-linked recessive allele.

Researchers often use mice to evaluate potential medications for treating human disease. If a medication is successful in the mouse model, it then must be further tested in human clinical trials. Which of the following best explains why clinical trials are necessary?

Mice and humans have only 80% genetic similarity.

Which ancestor of the modern-day horse is also the closest common ancestor to Parahippus?

Miohippus

What does it mean for a trait to be both polygenic and multifactorial?

Multiple genes each produce aspects of a trait, and environmental factors influence the expression of those genes.

If a man has an X-linked recessive disease, can his sons inherit that disease from him?

No, all his sons inherit their X chromosomes maternally

Can males be carriers of an X-linked trait?

No, because males have only one copy of the X chromosome

The fossil record indicates that the earliest known ancestor of horses has four toes. Modern horses have only one. Which of the following best explains why this occurred?

Offspring with genetic mutations resulting in fewer toes were more likely to survive and reproduce.

Which description is an example of the effects of rising temperatures?

Plants are blooming earlier in the year.

How are polygenic and multifactorial traits different?

Polygenic traits are genetically based, whereas multifactorial traits have both genetic and environmental influences.

Select the true statements about Mitochondrial Eve. Select the TWO answers that are correct.

She is the common female ancestor of all humans living today. No other mitochondrial DNA but hers has survived thousands of generations.

Why is mitochondrial DNA inherited only from mothers and not fathers?

Sperm do not contribute their mitochondria to the zygote during fertilization.

Scientists have studied patterns of mitochondrial DNA to determine where humans first evolved and how they spread. Humans inherit their mitochondrial genes only from their mothers. Why aren't a father's mitochondrial genes passed to his offspring?

Sperm do not contribute their mitochondria to the zygote.

Chimpanzees exhibit 99% genetic similarity to humans. Cows share approximately 80% of their DNA sequence with humans. Scientists can predict the relative age of a common ancestor using DNA sequences. Which of the following statements regarding molecular clocks is true?

The common ancestor of chimpanzees and humans lived more recently than the common ancestor of cows, chimpanzees, and humans.

Select the explanation for why a phenotype is selected for in the first environment but selected against in the second environment.

The phenotype leads to higher rates of survival and reproduction in the first environment but lower rates of both in the second environment.

What is meant by codominance?

The two alleles in a heterozygote each produce their own distinct phenotype equally.

What is different about red blood cells from a person with type AB blood, compared to those from other blood types?

They carry A and B type surface markers, so they are universal acceptors of blood.

Human activities such as deforestation increase the rate of climate change. Given the basic principles of the carbon cycle, which of the following is one explanation for why deforestation impacts global warming?

Through photosynthesis, land plants remove carbon dioxide from the atmosphere, thus large-scale removal of trees from the environment increases the greenhouse effect.

Select the statements that describe relationships between UV light, melanin, folate, and vitamin D. Select the TWO answers that are correct.

UV light is necessary for the production of vitamin D. Melanin in the skin shields folate from destruction by sunlight.

Of the following traits that are associated with being human, which evolved most recently?

a big brain

An organism's fitness depends on its _____.

ability to survive and reproduce

Why is the evolution of antibiotic resistance in bacteria happening so quickly?

because bacteria can reproduce so quickly because any use of antibiotics will select for resistant bacteria because of overuse of antibiotics in humans because of overuse of antibiotics in livestock

If two women have identical alleles of the suspected 20 height-associated genes, why might one of those women be 5 feet 5 inches tall and the other 5 feet 8 inches tall?

because environmental factors also play a role in the phenotype of this trait

Which of the following organisms contributes to reducing atmospheric CO2 levels?

both maple trees and most algae

Which greenhouse gas is emitted every time you breathe out?

carbon dioxide

What kind of inheritance occurs if red flowers crossed with white flowers produce offspring with red patches and white patches on their flower petals?

codominance

Fossils are generally going to be more useful for studying animals that lived in or near water (e.g., streams, lakes, oceans, etc.) because _____.

dead animals that fall into water are more likely to be in conditions that allow fossilization

The carbon cycle is the movement of carbon atoms via natural processes such as _____.

decomposition, photosynthesis, and respiration

An individual's genotype predicts an adult height of 6.5 feet, but that individual grows to only 5.5 feet in adulthood. What accounts for the difference in height

environmental factors

What are the two major mechanisms by which bacterial populations generate genetic diversity?

gene transfer and mutation

If bacteria reproduce through asexual reproduction, how does genetic variation occur?

gene transfer, mutations

What can we learn about vertebrate evolution from Tiktaalik that we did not know before?

how vertebrates evolved tetrapod limbs

A television show about conspiracy theories is discussing global warming, claiming it is a myth that CO₂ levels have risen over the last 1,000 years. Which evidence would be most useful to use in educating the producers to convince them that global warming is not a myth?

ice cores

What kind of trait produces pink flowers when red flowers are crossed with white flowers?

incompletely dominant

In the course of human evolution, which of the following environmental factors likely influenced whether a population had mostly light-skinned individuals or mostly dark-skinned individuals?

levels of uv lights

What meiotic event produces four gametes with abnormal numbers of chromosomes?

meiosis I nondisjunction

The relationship between global warming and greenhouse gases is the _____.

more greenhouse gases, the greater the amount of heat trapped from Earth's surface

In the late Devonian era, the seas began to recede and the land became more fertile. These environmental changes resulted in the emergence of land-dwelling vertebrates. Some animals are better able to survive and reproduce under changing environmental conditions. This is an example of:

natural selection

Which of the following biomes covers the greatest amount of Earth's surface?

oceans

Although all organisms share the same four nucleotides, it is the _____ of these nucleotides that makes each species unique.

sequence

What causes nondisjunction during meiosis II?

sister chromatids fail to separate

A bacterial cell with which modification might be resistant to antibiotics such as methicillin?

the ability to produce an enzyme that breaks down the antibiotic

The fossil remains of <i>Ardipithecus ramidus</i> showed that _____.

the ability to walk upright preceded the evolution of a larger brain

Which of these is a part of the ecosystem of Vermont's maple sugar-providing region?

the air the temperature maple trees the soil

In strains of bacteria that are not resistant to beta-lactams, which part(s) of the bacterial cells are disrupted by the antibiotic?

the cell walls

What is the environmental pressure in the case of antibiotic resistance?

the presence or absence of antibiotics in the environment

What is the result of binary fission?

two daughter cells with genetic material identical to that of the parent cell

The taiga biome is characterized by evergreen trees, whereas the temperate forest biome is characterized by evergreens and trees that drop their leaves during the winter. Which of the following features accounts for these differences in plant life? Select the TWO answers that are correct.

variation in temperature ranges differences in amount of annual precipitation