CH 22

What is biological fitness? Hint: Biological fitness is not physical fitness. What is it?

Biological fitness measures the reproductive success of an individual relative to others in the population. Biological fitness is a measure of reproductive success. The term relative refers to the fact that natural selection favors the heritable traits of individuals who have greater reproductive success than other individuals in the population.

In the projected video showing the growth of bacteria, why did the bacteria grow up to the edge of the area with antibiotics, pause, then continue to grow across the area with antibiotics?

A few bacteria experienced random mutations in their DNA, which allowed some of them to grow even though antibiotics were present.

Which of the following correctly describes what the video referred to as a "microbial cure"?

Antibiotics are used to kill all of the infectious bacteria in a person.

Does the ability of a Mycobacterium tuberculosis cell to infect a new host depend on its drug-resistant phenotype? Hint: Think about how tuberculosis is spread.

No, drug-susceptible cells and drug-resistant cells are equally likely to infect a new host. A cell's drug susceptibility or resistance does not affect its ability to infect another host, although a cell's drug resistance would increase that cell's chances to spread in an environment containing antibiotics due to increased survival.

If the bacterium Staphylococcus aureus experiences a cost for maintaining one or more antibiotic-resistance genes, what would happen in environments that lack antibiotics?

These bacteria would be outcompeted and replaced by bacteria that have lost these genes.

In the video, what does the UK's Chief Medical Officer suggest for promoting the development of new antibiotics?

encouraging big pharmaceutical companies to start investing again in new drug research and development

Traits that are derived from a common ancestor, like the bones of human arms and bird wings, are said to be _____.

homologous

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

Which of the following contributes the LEAST to the problem of antibiotic resistance?

taking the entire course of antibiotics as prescribed by the doctor

How did thorns originate in roses?

A spontaneous mutation resulted in thorns and increased this rose's resistance to herbivory, so it was selected by natural selection to become dominant in the population. Natural selection can only select upon variation that is already present.

According to data presented in this chapter, which of the following statements is correct?

Evolution is not progressive.

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.

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.

After his journey on the HMS Beagle, Darwin made this now-famous sketch in his notebook. Which ideas does it represent?

Species descend from other species just as naturally as children come from parents. All species are connected to one another in a "family tree." All species are linked to one another by common ancestry. Darwin's simple drawing shows his thinking: any species can give rise to new species with different features. This is what Darwin described as "descent with modification."

Which statement about adaptation is correct? Hint: What is the difference between adaptation and other forms of evolutionary change?

The adaptive value of a trait varies as the environment changes. Adaptive value is tied to a particular set of environmental conditions. If environmental conditions change, the value of a particular trait may also change.

How do lactase supplements help people who are lactose intolerant?

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

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.

A relative acquired the infection from this patient prior to his death but after the patient relapsed. Would the relative's infection be resistant to rifampicin therapy? Hint: What causes drug resistance?

Yes. The bacteria acquired from the patient would likely be drug resistant and would pass this trait onto their offspring. This mutation is heritable.

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.

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true?

Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted.

Which of the following statements describes the evolution by natural selection of Mycobacterium tuberculosis bacteria in their new environment? Hint: The bacteria have evolved by natural selection to better "fit" their environment.

The drug-resistance trait is an adaptation to the environment in which human hosts are medicated with the antibiotic rifampin. Bacterial cells have higher fitness when they are drug resistant in the new environment in which people have been medicated with antibiotics.

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

Biological fitness is best defined as

the ability of an individual to produce offspring that survive and reproduce, relative to other individuals in the population.

Coral reefs are biodiverse ecosystems that provide food, income, coastal protection, and many other services to millions of people. Yet coral reefs are under threat from human impacts such as climate change−many corals cannot tolerate the warming ocean water and have suffered massive "bleaching" events, which can be fatal. Researchers have discovered that some corals have the capacity to acclimatize to warmer water, while other corals do not. The researchers fear that because corals are long-lived colonial animals and thus evolve slowly, they may not be able to adapt to global warming fast enough to avoid extinction. How does the difference between acclimatize and adapt is important to the fate of corals?

Acclimatization does not change genotype, so traits that arise via acclimatization cannot be passed on to offspring. On the other hand, an adaptation CAN be passed on to offspring, which means that adaptations can drive evolution. If an individual coral colony can acclimatize to the warming water, this means it might survive as the ocean continues to warm. Individuals that cannot do it will die. It is important for these changes to become inherited. Natural selection will favor corals that have these characteristics that enable them to tolerate warm water. So, over time, coral populations will adapt to warm water.

Over time, bacteria have become increasingly resistant to antibiotics. Which of the following best explains this in terms of natural selection?

Bacteria that happen to have natural resistance to antibiotics survived and reproduced.

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? Hint: What did Darwin postulate was required for natural selection to occur?

Birds that could eat larger, tougher seeds survived and reproduced during the drought. Beak size varies among the birds in the finch population under study. Beak size is an inherited trait in the finch population under study. - Darwin suggested that evolution by natural selection requires that a trait must be heritable, so that alleles that encode a favorable trait can be passed on to offspring; a trait must exhibit variation within the population; for any given environmental condition, certain heritable traits make it more likely that some individuals will survive and reproduce than others. Evolution by natural selection does not occur because existing individuals acquire new characteristics in response to an environmental change. During the drought, for example, the beaks of individual finches did not become larger. Also, with a few rare exceptions, environmental changes do not induce mutations (either favorable or unfavorable) in a population. Rather, the population already exhibits a range of variations for any given trait (a range of beak sizes, for example) that natural selection can act on.

Darwin and Wallace made independent observations in different parts of the world. Which statements are true?

Both collected huge numbers of specimens and realized that individuals vary within species. Both observed slightly different species on nearby islands and concluded that species could change over time. Both witnessed nature up close and realized it was a battlefield with massive casualties. Darwin and Wallace observed similar fact patterns in nature and came to the same explanation about the origin of species.

Predict how prickles ("thorns") originated in roses.

By chance, a mutation occurred in some roses that resulted in sharp bumps on the stems. Individuals with these early prickles survived herbivore attacks and produced more offspring than roses without the mutation, increasing the frequency of the prickled roses in the population over time. Note that roses cannot cause a mutation to occur because they want or need it.

Why does natural selection not produce populations that are perfectly adapted to their environment? Hint: Consider the circumstances that limit the effectiveness of natural selection.

Changing environments may change the nature of adaptive traits in a population. No single trait is optimal in all environments, and natural selection may favor different traits as the environment changes.

Which of the following statements is an accurate combination of postulates 1 and 2 of natural selection? Hint: Both of these postulates are required for natural selection to occur. Pick the statement that would enable evolution by natural selection.

Heritable variation exists for traits among individuals in a population.

These phylogenetic trees represent two interpretations of the origin of hair in humans and dogs in which hair is or is not homologous in humans and dogs. For each interpretation, did the most recent common ancestor of humans and dogs have hair? Which tree is correct?

If hair is homologous in humans and dogs (left tree), their most recent common ancestor did have hair. If hair is not homologous in humans and dogs (right tree), their most recent common ancestor did not have hair. The left tree is correct. The bar on a branch of a phylogenetic tree symbolizes the origin (or loss) of a homologous trait like hair. All the organisms to the right of that bar are assumed to possess that trait. The nodes (branching points) on the tree represent the most recent common ancestors. The node for humans and dogs is to the right of the bar in the correct left tree; therefore, the common ancestor had hair.

Which of the following statements is an accurate combination of postulates 3 and 4 of natural selection? Hint: Both of these postulates are required for natural selection to occur. Pick the statement that is a prerequisite for evolution by natural selection.

Individuals experience differential success in their ability to survive or reproduce due to differences in certain traits. Variation in fitness is required for selection to change the characteristics of a population over time. Remember that selection also requires that the variation in fitness be related to a heritable trait.

Identify the four postulates of natural selection. Hint: Consider the four steps in the process of natural selection.

Individuals in a population vary in the traits they possess. Survival and reproductive success are variable among individuals in a population. Individuals with certain traits are more likely to survive and reproduce. Some trait differences are heritable. Darwin's four postulates can be summarized as follows: -Individuals in a population vary in the traits they possess. -Some trait differences are heritable. -Survival and reproductive success are variable among individuals in a population. -Individuals with certain traits are more likely to survive and reproduce.

The fossil record resembles the living species in the same geographic area. How does this pattern, also known as the law of succession, support the theory of evolution by natural selection?

It is evidence that species can change over time. It shows that the fossil species group is not a random assemblage but is the precursor to the modern assemblage.

What did Wallace conclude from observing that the bones in manatee flippers look similar to the bones in a human arm and hand?

Manatees' arm and finger bones are evidence that manatees share a common ancestor with land mammals. For Wallace, the unnecessary arm and finger bones in manatee flippers show that they descended from an ancestor with arms. These vestigial structures are evidence that every species is a modified form of an older species.

When Charles Darwin set sail on the HMS Beagle, what did he and most of his contemporary scientists think about the origin of species?

Most scientists, including Darwin, thought each species was specially created by God in its present form and did not change over time. Special creation was the prevailing idea of the time. Darwin, like most other scientists, began his journey believing species were unchanging and specially created by God.

A particular antibiotic kills 99% of a bacterial population. What will be the result of the continued application of this antibiotic?

Over time, the antibiotic will become less effective at killing the bacteria.

Which observations led Darwin to establish a relationship between extinct and living animals?

The bony shells of armadillos resembled the shells of ancient Glyptodon fossils. The fossilized remains of giant sloths were found in places where smaller sloths now live. Darwin puzzled over why he found fossils of extinct animals in places where he found similar, living animals. Eventually, these observations supported his idea that today's species descend from older, extinct species.

In the United States today, about half of the corn crop is genetically engineered with a protein that is toxic to corn borers, an insect pest of corn. Which of the following conditions would be necessary for evolution of resistance to the toxic protein to occur in the corn borer? Hint: Consider the four postulates of natural selection.

The corn borer must have or generate (by mutation) heritable variation in resistance to the toxic protein. The resistant corn borers must survive better or reproduce more than nonresistant corn borers. If all these conditions are true, then the corn borer might evolve resistance to the toxic protein.

The Grants routinely tagged every ground finch on the island and took detailed measurements of the birds' weight, body size, and beak size.

The gray bar highlights the 1977 drought year. The thin "I-beams" surrounding each data point on this graph indicate the standard error of each data point--a statistical analysis of the uncertainty in the calculation of an average. Notice that the standard error bars for the years 1974-1977 overlap; this suggests that the variations in average beak size for those years can be attributed to random processes, and is not statistically significant. In contrast, the lack of any overlap between the standard error bars in the years before and after the drought indicates that the increase in the average beak size was not a random process. (Compare the standard error bars from 1974-1976 with those from 1978-1981.) The Grants hypothesized that this increase in beak size resulted from the change in environmental conditions.

What is the concern about using antibacterial and antimicrobial soaps?

The use of any chemical that kills bacteria can eventually lead to resistance to that chemical in the population of bacteria.

As Wallace traveled the Malay Archipelago, he noticed that western islands had placental mammals, like monkeys. Eastern islands had marsupial mammals, like kangaroos. How did Wallace explain this distribution?

The western islands were once connected to Asia and the eastern islands had been connected to Australia. The islands had never been connected to each other. Different kinds of animals were restricted to different regions because species come from pre-existing, nearby species. Because the western islands were once all connected, they would have the same species, which are also found in the mainland in Asia. The eastern islands were once also all connects and had the same species, which are also found in Australia.

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?

Their genomes should be more similar to each other than are the genomes of the five tree finch species.

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)? Hint: What selective pressure was working on beak size in the years after the drought? Natural selection in similar environments

This graph shows the actual data the Grants collected in the 25 years after the drought. The horizontal bar highlights the range of beak sizes that were present in the population prior to the 1977 drought. Notice that from about 1987 on, average beak sizes fall within that range once again. Because the environment returned to its stable, pre-drought conditions, you should expect that the average beak size would also return to its pre-drought level, which the Grants observed to be the case. This implies that larger beaks are not as well adapted to eating smaller seeds--a fact that explains why larger beaks were not as common as smaller beaks before the 1977 drought.

Darwin and Wallace independently arrived at the same conclusion that species change over time. Which observations supported their conclusions?

Tortoises from different Galapagos islands have distinct shells. The fossilized remains of giant sloths were similar to the smaller, living sloths Darwin encountered. Bird families clustered geographically: cockatoos in the Malay Archipelago and Australia, macaws and hummingbirds in the Americas. Birdwing butterflies were found throughout the Malay archipelago, but species differed slightly from island to island. Mockingbirds from different Galapagos islands had subtle, consistent differences. The bony shells of armadillos resembled fossilized shells from the extinct Glyptodon. The resemblance between species and the variations among distant species led both Darwin and Wallace to conclude that species change over time.

A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the triazine works well and almost all the pigweed dies; but after several years, the farmer sees more and more pigweed. Which of these explanations best explains what happened?

Triazine-resistant weeds were more likely to survive and reproduce.

True or false? It would be difficult to assess whether the drug-susceptible or drug-resistant phenotype in a population of Mycobacterium tuberculosis was more fit in an environment without antibiotics. Hint: Consider the Darwinian fitness of these bacterial cells.

True In an environment without antibiotics, individual cells probably would not differ in their reproductive rates or their survival. Without the application of the drug (antibiotic), it would be very difficult to analyze any differences—one wouldn't even be able to sort the cells!

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?

Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.

Which statement shows population thinking? Hint: What is the difference between a population and a species?

Variation among individuals in a species is real and important. It was once thought that variation within a species represented flaws or imperfections. In Darwinian thought, variations are real and are important because natural selection can act to favor some variations over others.

Which of the following is a correct application of one of Darwin's postulates to the Galapagos finch data from Case Study #2? Hint: Two of Darwin's postulates are linked to heritable variation and two are linked to reproductive success.

Variation in beak size was present in the population of finches prior to the start of the study. Beak depth varied from 6cm to 14cm in 1975.

Explain why the overprescription of antibiotics by doctors, or the overuse of everyday soaps containing antibiotics, can be a health risk.

When antibiotics are overused, susceptible bacteria are constantly being killed off, even when an infection is not present. However, any individual bacteria that are resistant to these antibiotics will survive and multiply, reducing the likelihood that antibiotic treatment will be effective in the future.

Explain why the overprescription of antibiotics by doctors, or the overuse of everyday soaps containing antibiotics, can be a health risk.

When antibiotics are overused, susceptible bacteria are constantly being killed off, even when an infection is not present. However, any individual bacteria that are resistant to these antibiotics will survive and multiply, reducing the likelihood that antibiotic treatment will be effective in the future. Antibiotic resistance increases over time because resistant bacteria become more and more common. Overuse of antibiotics has accelerated this process and resulted in the need for newer and often stronger antibiotics.

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?

White- and black-winged beetles have equal fitness.

In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20 percent of the β hemoglobin alleles in the human gene pool. The sickle-cell allele is pleiotropic (i.e., it affects more than one phenotypic trait). Specifically, this allele affects oxygen delivery to tissues and affects one's susceptibility to malaria. Heterozygous individuals who have one normal and one sickle-cell allele have a phenotype that has both costs and benefits. The cost: Under conditions of low atmospheric oxygen availability, individuals heterozygous for this allele can experience life-threatening sickle-cell "crises." The benefit: Such individuals are less susceptible to malaria. Thus, pleiotropic genes/alleles reveal that ________.

adaptations are often compromises

Cotton-topped tamarins are small primates with tufts of long white hair on their heads. While studying these creatures, you notice that males with longer hair get more opportunities to mate and father more offspring. To test the hypothesis that having longer hair is adaptive in these males, you should _____.

determine if hair length is heritable