Mastering Biology - 23.3-23.4 Review

How do these molecular and cellular events lead to emergent properties at the individual and population levels of biological organization? Match the terms in the left column to the appropriate blanks in the sentences on the right. Terms can be used once, more than once, or not at all.

HETEROZYGOTES ERYTHROCYTES DOMINANT RECESSIVE HIGH HETEROZYGOTES HOMOZYGOTES

Part E: Which discovery supports the hypothesis that evolution of the lactase-persistence trait was driven by the use of milk in pastoralist cultures?

Ancient pots used to hold milk are about the same age as the lactase-persistence mutations.

Part G: As you have determined from the simulation, beak size in ground finches is directly related to annual precipitation. Which of the following graphs best represents the relationship between annual precipitation and most frequent beak size in the Galapagos ground finch?

D : decreasing graph

Part B: Why is the enzyme lactase necessary to digest dairy products?

Lactase breaks down lactose into smaller molecules that can be absorbed by the cells that line the small intestine.

Part F: How could milk-drinking have provided strong favorable selection for lactase persistence? Select all that apply.

Milk was safer to drink than water and reduced exposure to pathogens. Milk is protein and fat-rich and therefore could have been an important, high-quality food source. Milk may have been a critical food source during times of famine.

Part G: Predict what will happen to the frequency of the sickle cell allele in areas where malaria has been eradicated.

The sickle cell allele will decrease in frequency.

Part G: Lactose intolerance in infants is more common in the population today than it was a hundred years ago. Why?

Today there are alternatives to breast milk, such as lactose-free formula and soy milk, so lactose intolerant infants can survive.

Part D: When should a lactase supplement be taken in order to be most effective, and why?

at the same time the dairy product is consumed, so that the lactase will be in contact with the lactose

How is the process of evolution revealed by the imperfections of living organisms? Select all that apply.

- Imperfections in organisms result from a variety of other constraints, such as a lack of genetic variation for the trait. - Organisms inherit a basic form from their ancestors, and that form is modified by natural selection over time. This form is usually not perfect.

Part A: In the beetles described in the animation, there were two alleles for color, brown and green. Suppose that you discover a very small population of these beetles, consisting of the individuals shown below. How can you calculate the frequency of each allele in this population? Drag the terms or numbers on the left to the appropriate blanks on the right to complete the sentences. Not all terms will be used.

1. brown alleles 2. 8 3. 20 4. 0.4 5. 0.6

Part C: Now use the simulation to see what happens in dry years. - Set the amount of precipitation to 10 mm. -Run the simulation 5 times and take note of the distribution of beak sizes in the bar graph for each run. The bar graph represents the distribution of beak sizes after 12 years at the set precipitation level. Which range of beak depths was most frequent after 12 years?

11 - 12mm

Part B: To determine how precipitation affects beak size, you will manipulate the annual amount of precipitation on the island where the ground finches live. - Reset the simulation to its default setting. This will set the precipitation to 50 mm per year. - Run the simulation 5 times and take note of the distribution of beak sizes in the bar graph for each run. The bar graph represents the distribution of beak sizes after 12 years at the set precipitation level. Which range of beak depths was most frequent after 12 years?

9 - 10mm

Part B: How does the term "lactase persistent" relate to the term "lactose tolerant"?

A lactase-persistent person is lactose tolerant.

You read about soapberry bugs and select the correct statement describing relative fitness in these individuals.

A soapberry bug with high relative fitness has a relatively high number of offspring that survive to reproductive age. Submit

Part A: Why should we not view lactose intolerance as a disease in adult humans?

Adult humans did not consume dairy products until fairly recently in our evolutionary history.

Part B: How did the drought lead to an increase in beak size in the medium ground finch population? The Grants reasoned that - prior to the drought, the finch population fed primarily on small seeds that they could open easily. Although larger, tougher seeds were available, they were not typically eaten, not even by finches with larger beaks. - during the drought, only a limited number of small seeds were produced, leaving mostly larger, tougher seeds available for food. Finches that were unable to eat the larger seeds died of starvation. Based on their observations and the data they collected, the Grants concluded that evolution by natural selection had occurred in the medium ground finch population. The increase in the average beak size of the offspring was a direct result of the change in the food supply during the drought. In order to have reached this conclusion, the Grants must have either assumed or proven that several other facts about the finch population were true. Which statements represent information that must be true in order for the Grants conclusion to be correct? Select the three statements that must be true.

Beak size varies among the birds in the finch population under study. Birds that could eat larger, tougher seeds survived and reproduced during the drought. Beak size is an inherited trait in the finch population under study. Submit

Part D: Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today?

Directional selection

Part A: Which type of selection tends to increase genetic variation?

Disruptive selection

Part F: Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers?

Disruptive selection

Part C: How did Dr. Allison test his hypothesis that sickle cell disease was connected to malaria? Select all that apply.

He expanded his study area beyond Kenya to the rest of East Africa to see if malaria and sickle disease were connected. He evaluated blood samples for malaria parasites and the presence of sickle cells.

Part B: In 1949, Dr. Tony Allison observed a high frequency of Kenyans carrying the sickle cell allele in coastal areas and near Lake Victoria, but a lower frequency in the highlands. What did he hypothesize?

He hypothesized that there was a connection between malaria and sickle cell disease.

Part F: How does Dr. Allison's work provide an example of natural selection in humans? Select all that apply.

In areas with malaria, individuals with one sickle cell allele reproduced at higher rates than those with no sickle cell alleles. In areas without malaria, individuals with two sickle cell alleles reproduced at lower rates than those without sickle cell disease.

Part E: In some populations, 1 in 500 people have sickle cell disease. What reason does the film give for why a potentially deadly, inherited disease is found at such high frequencies?

Individuals with one sickle cell allele are protected from malaria and do not have sickle cell disease, thus keeping the allele in the population.

How does diploidy help to preserve genetic variation?

It allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes.

Part D: What did researchers discover about the genetic mutation causing lactase persistence?

It is found in a regulatory region (a "switch") upstream of the lactase gene.

Part F: Most people are lactose intolerant as adults, but nearly everyone produces sufficient lactase as an infant. However, in some cases, genetic mutations can occur that make an infant lactose intolerant. From an evolutionary perspective -- over thousands of years -- why would lactose intolerance in infants be very rare in the population?

Lactose intolerant infants could not digest breast milk and therefore usually died, never having the chance to pass the mutation on to their children.

Part B: The three major mechanisms of evolution differ in how they work, and as a result often have different effects on a population. Review your understanding of natural selection, genetic drift, and gene flow by sorting the statements below into the correct bins. Drag each statement into the appropriate bin depending on whether it applies to natural selection, genetic drift, or gene flow.

Natural Selection: -consistently causes a population to become better adapted to its environment -a result of differential success in reproduction -cannot cause a harmful allele to become more common Genetic Drift: -can result from the founder effect -causes allele frequencies to fluctuate randomly -can result from the bottleneck effect Gene Flow: -a result of the movement of fertile individuals or their gametes -can introduce new alleles into a population's gene pool

Part C: Four individuals measured their baseline blood glucose, then drank a litre of milk. They then measured their blood glucose levels at regular 15 minute intervals for 60 minutes. The results are shown in the graph below. Which individuals are lactase-persistent? Selects all that apply.

Sarah Peter

Part A: Compare sickle cell disease and malaria.

Sickle cell disease and malaria are both potentially lethal diseases.

Part E: Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies?

Stabilizing selection

Part G: Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards?

Stabilizing selection

The fruit fly Drosophila melanogaster has an allele that confers resistance to DDT and similar insecticides. Laboratory strains of D. melanogaster have been established from flies collected in the wild in the 1930s (before the widespread use of insecticides) and the 1960s (after 20 years of DDT use). Lab strains established in the 1930s have no alleles for DDT resistance. In lab strains established in the 1960s, the frequency of the DDT-resistance allele is 37%. Which statement is correct?

The evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread.

Part E: You can see from the stacked area graph that in the first two years of low precipitation, the percentages of birds with the smallest beaks went down and the percentages of birds with the largest beaks went up. What happened to the percentages of ALL the beak sizes after two years?

The percentages of all beak sizes leveled off.

Part D: So far, you may have focused on the bar graph. Now let's shift your attention to the stacked area graph, which shows how beak depth frequencies changed in the ground finch population over 12 years. - Run the simulation again at 10 mm of annual precipitation. The stacked area graph shows how the population changes over 12 years at 10 mm of annual precipitation. - Focus on the first two years of the graph. - Use the slider on the graph to see the percentages of finches with different beak depths at a specific year. What happened to the percentages of 6 mm and 7 mm beaks in the first two years?

The percentages of the smallest beak sizes went down.

Part D: If a person has two normal copies of the hemoglobin allele, which statements are true? Select all that apply.

The person is homozygous at the hemoglobin locus. The person is susceptible to malaria.

Part C: How do lactase supplements help people who are lactose intolerant?

The supplements provide the enzyme that breaks down the lactose in dairy products. Submit

Which statement correctly describes the role of chance in evolution?

The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism's DNA.

Part B: In a bell-shaped curve, the x-axis (horizontal direction) of the graph represents which of the following?

The value of a particular characteristic; characteristics of an organism can include such traits as size and color.

Part G: Suppose that a mutation for lactase-persistence occurred in each of the populations described below. In which populations would the mutation be more likely to increase in frequency over time because of natural selection?

a population that raises wheat and sheep

Part C: Populations evolve for many reasons. Suppose there is a population of plants that have either purple flowers or white flowers, and the allele for purple flowers is dominant. This means that plants with two purple alleles have purple flowers. Plants with one purple allele and one white allele also have purple flowers. Only plants with two white alleles have white flowers. For each event or condition described below, answer the following questions. - Which mechanism of evolution is at work? - How does this event affect the population's gene pool? Do the frequencies of the two alleles change, and if so, how? Drag the labels to their appropriate locations in the table below. - Drag the labels of Group 1 to indicate which mechanism of evolution is at work. - Then drag the labels of Group 2 to indicate the effect on allele frequencies. Labels can be used once, more than once, or not at all.

a.) natural selection b.) frequency of white allele increases c.) genetic drift d.) frequency of purple allele increases e.) genetic drift f.) allele frequencies change but not predictably g.) natural selection h.) frequency of purple allele increases i.) gene flow j.) frequency of white allele increases

In evolutionary terms, an organism's relative fitness is measured by its __________

contribution to the gene pool of the next generation

Part C: Although the Grants did not begin their study of the finch population until the early 1970s, there is enough information to assume that prior to the 1977 drought, rainfall was sufficient and the finch population thrived by eating abundant, smaller seeds. It is also assumed that during that period of time, no other environmental changes affected the finch population. After 1977, rainfall amounts returned to their normal pre-drought levels for the next 25 years. Smaller seeds were once again abundant on the island. Which graph shows your prediction of how the finch population's average beak size changed in the 25 years after the drought (shown in red)?

decrease, increase, decrease

Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to __________.

directional selection

Part C: True or false? Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population.

false

What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population?

founder effect

Allele frequencies in a gene pool may shift randomly and by chance. What is this random shift called?

genetic drift

One population of a species has 25 individuals, all with genotype AA; a second population of this species has 40 individuals, all with genotype aa. Assume that these populations live far apart but in similar environmental conditions. Based on this information, the observed genetic variation most likely resulted from

genetic drift

Part A: The enzyme lactase breaks the sugar lactose into which compound(s)? Select all that apply.

glucose galactose

Part A: Use the data to make a graph showing the changes in beak size that the Grants observed. To create the graph, first click on "Add Element" and select the label "Average Beak Size By Year."

graph the table

Part E: In which country would you most likely find a higher incidence of lactase persistence?

in a Scandinavian country where people historically raised dairy cattle and made cheese

What is the only evolutionary mechanism that consistently leads to adaptive evolution?

natural selection

Part A: Natural selection, the process by which certain characteristics in a population change in response to environmental changes, is one of the main principles of Darwin's theory of evolution. In order to understand how evolution works in populations, it is important to understand the main concepts. Place the terms in the appropriate blanks to complete the sentences.

population variation adaptations natural selection allele frequencies

Part F: Now run the simulation to see what happens in wet years. - Set the amount of precipitation to 100 mm. - Run the simulation 5 times. - Use the graphs to fill in the following sentences. Place the terms in the appropriate blanks to complete the sentences.

small beaks large beaks equilibrium most abundant lest abundant evolution