Mastering Biology Chapter 13
The Grants witnessed strong selection during droughts in 1977 and 1985. Compare the two droughts
-Both droughts resulted in changes to food sources that favored the survival of some medium ground finches over others -Both droughts events provided strong natural selection on medium ground finch populations
In 1977, medium ground finches on Daphne Major experienced a severe drought. The figure shows the beak depth of the initial population before the drought (red bars) and of the drought survivors (black bars). What do the data show?
-Finches with larger beaks had a survival advantage in the 1977 drought -More than one-half of the initial population died during the drought -The most common beak size of the initial population was 8.8mm. A very small proportion (~5%) of the initial population with this beak size survived
The film defines species as populations whose members don't interbreed. What keeps different Galapagos finch species from mating?
-Geographic isolation and different environments led to changes in traits that affected mating -Males only court females that have similar beak and similar size -Individuals recognize and only respond to songs of their own species
How did Dr. Allison test his hypothesis that sickle cell disease was connected to malaria?
-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
How does Dr. Allison's work provide an example of natural selection in humans?
-In areas without malaria, individuals with two sickle cell alleles reproduced at lower rates than those without sickle cell disease -In areas with malaria, individuals with one sickle cell allele reproduced at higher rates than those with no sickle cell alleles
Which of these gametes contain one or more recombinant chromosomes
B, C, F, and G
Change in Population
Brown beetles survive to reproduce more than green beetles do. The brown allele increases in frequency
Which of the following is(are) homologous to the bones in this image?
Dark brown cat digits are homologous to the whale bone
Different finch species have beaks of different shapes and sizes. What do these beak differences tell us?
Different finch beak shapes are evidence that finch species adapted to different environments over many generation
A large population of mice is isolated on an island. There are two varieties of the mice, brown and gray. Their fur colors closely match the gray rock outcrops and brown soils of the island. Hawks are their main predators. This situation most likely reflects the outcome of
Disruptive Natural Selection
Imagine that four people are infected with HIV from a common source (an infected blood sample). Initially, the patients' HIV populations are genetically identical. By the time they develop full-blown AIDS, how would the viral populations of the fourpatients compare?
Each patient's viral population would be unique, specifically adapted to deal with - and overcome - his or her unique immune system responses
True or False. In the example described in the tutorial, the red amoebas survived the catastrophic event, and all future generations of amoebas were red because the red amoebas had a higher reproductive rate than the blue ones
False
New individuals move into a population
Gene flow
Color is an inherited trait in beetles. If brown beetles move into a population from a nearby island, which of the following statements is correct?
Gene flow causes the frequency of the brown allele to increase
Which of the following are causes of evolutionary change?
Genetic drift, natural selection, gene flow, mutation
Selective Pressure
Green beetles are more visible to birds than brown beetles, so birds eat more green beetles
Remember that color is an inherited trait in beetles. Which of the following is an example of natural selection?
Green beetles leave more offspring than brown beetles because they are better at finding food
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
Which of the following is a true statement about Charles Darwin?
He proposed natural selection as the mechanism of evolution
As proposed by Darwin, what sorts of traits are favored by natural selection?
Heritable traits that help individuals survive and reproduce more successfully than other in the same population
When dark-colored fur gives mice a 1% competitive advantage and 1% of the population begins with dark fur, in about 1000 years, 95% of the population will have dark fur. Which of the following statements is true?
If dark-colored rock pocket mice had a competitive advantage of 0.1%, it would take longer for 95% of the population to have dark fur
Which example below presents a misconception about how antibiotic resistance develops?
Individual bacteria and viruses become immune to antibiotics after they are exposed to them. Eventually the antibiotics are useless.
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
Which of the following statements about the amoeba population described at the end of the tutorial is true?
It is more vulnerable to extinction due to lack of genetic variation
Genetic evidence supports which of the following explanations for the presence of 13 different finch species on the Galapagos islands?
Many years ago, a small population of a single finch species migrated to the islands and evolved into the current 13 species
Camouflage enables this insect to evade predators
Natural selection
Natural selection and evolution are two terms that are sometimes confused, even by first year biology students. What is the relation between natural selection and evolution?
Natural selection is one of several mechanisms of evolution
Which of the following is a misconception regarding natural selection?
Natural selection progressively refines organisms' adaptations, eventually leading to perfection
Environmental Change
Pesticide is applied to a population of insects
A geneticist studied a large grass population growing in an area of erratic rainfall and found that plants with alleles for curled leaves reproduced better in dry years and plants with alleles for flat leaves reproduced better in wet years. This situation would __________.
Preserve the variability in the grass population
Compare sickle cell disease and malaria
Sickle cell disease and malaria are both potentially lethal diseases.
Selective Pressure
Some insects have a gene that makes them resistant to the pesticide. These insects survive. Insects without the gene die
Small lizards have difficulty defending their territory, but large lizards are more likely to be preyed upon by owls. Which type of selection would act on body size in these lizards under these conditions?
Stabilizing selection
The human immune system cannot effectively suppress the HIV virus on its own. What key feature of HIV makes it so hard to beat?
The HIV virus has an extremely high rate of mutation
In the normal course of evolution and adaptation, what is the most likely way for wings to develop in a tetrapod (four-limbed organism)?
The forelimbs (or possibly hind limbs) will be used for the new purpose of flight. This new function will arise through many gradual steps, and there will be aspects of the wing that reflect its history and are not perfectly suited for flight
Which best describes the fossil record?
The fossil record is the highly ordered sequence in which fossils are found in layers of sedimentary rock.
The top figure shows beak sizes of the 1976 finch population before the drought of 1977 (red bars) and after the drought (black bars). The lower figure shows the beak sizes of the offspring of the drought survivors in 1978. What do these figure
The overall beak depths of the 1978 offspring population are larger the original 1976 population
Consider a hypothetical insect population of 100 individuals. Two equally represented alleles (A and a) exist for a particular gene. Which scenario is an example of microevolution in this population?
The population is exposed to a toxin that kills individuals with the A allele. After exposure to the toxin the population has 25 surviving individuals, and 95% of them have the aa genotype.
A population of small fish lives in a lake with a sandy bottom. Large shore birds prey on these fish. Although most of the fish are the same light brown color as the sandy lake bottom, about 10% are mottled. A construction company dumps a load of gravel in the bottom of the lake, giving it a mottled appearance. Which outcome would you predict?
The proportion of mottled fish will increase over time
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
Change in Population
The surviving insects reproduce. The frequency of resistant insects in the population increases
Why do dark-colored rock pocket mice on dark lava flows have white bellies?
There is no selection for dark bellies by visual predators
Why did dark-colored rock pocket mice first appear in a population of light-colored rock pocket mice?
They have a genetic mutation that affects their fur color
How did the Grants test their hypothesis that differences in birds' songs can keep different species of finches from breeding with one another?
They played the songs of medium ground finches and cactus finches through a loudspeaker to see which species responded to each song
Has microevolution occurred? Why or why not?
Yes, because the allele frequencies have changed
Mutations are always ______
a change in an individual's DNA
Natural selection is best described as ________
a filtering process that fine-tunes the traits of populations by sorting among existing, randomly produced variations
This unequal reproduction in a population leads to the gradual accumulation of ________ to the environment.
adaptations
A(n) ________ is an alternative version of a gene
allele
In natural selection, _______ determine which phenotypes are successful
current conditions in the local environment
________ favors phenotypes at one end of a range and is common in periods of environmental change
directional selection
In a species of snail, dark-shelled individuals are better hidden from bird predators in the shady forest, while light-shelled individuals are better hidden in well-lit brushy edge areas. If there were no areas of intermediate brightness in this habitat,which type of selection would act on shell color in these snails?
disruptive selection
_______ favors phenotypes at both ends of a range over intermediate phenotypes. This type of selection may occur when the habitat is varied
disruptive selection
The ______ of life arises from the adaptation of species to different habitats over long spans of times
diversity
The wing of a bat is homologous to the _________ of a whale
flipper
The ease with which humans travel across the globe is likely to increase
gene flow
All the genes in a population are that population's
gene pool
The total collection of alleles in a population at a given time is the population's ______
gene pool
Modern travel along with migration reduces the probability of _____ having an effect on the evolution of humans.
genetic drift
The evolution of populations due to chance is
genetic drift
by chance, some wildflowers in this population reproduce, while others do not
genetic drift
In a population with brown and green alleles for color, genetic drift
has more effect on the evolution of a small population
Which of the following events could NOT be caused by a population bottleneck?
increased population size
Two key observations underlying natural selection are that members of population vary in their ________ and that all species can produce more offspring than the environment can support
inherited traits
___________ is a type of sexual selection in which individuals of one sex (usually males) compete directly for mates. This may involve ritualized displays or physical combat
intrasexual selection
In a type of sexual selection often called _________, individuals of one sex (usually females) are choosy in selecting their mates. This choice is often based on the showy appearance or behavior of the male
mate choice
Homologous pairs of chromosomes are lined up independently of other such pairs during
metaphase I
Changes in allele frequencies in a population over time is ______
microevolution
Generation-to-generation change in the allele frequencies in a population is ________
microevolution
The phrase Darwin used to describe his broad theory of evolution is "descent with _______"
modification
A(n) _________ is change in the nucleotide sequence of DNA
mutation
Of the choices listed below, which contributes the most to genetic variation among individuals in most prokaryote species?
mutation
A prominent tail helps the peacock attract a mate
natural selection
Darwin proposed a mechanism for how evolution occurs, which he called ________
natural selection
the bird's beak is well-suited for cracking seeds
natural selection
Crossing over, resulting in an increase in genetic variation, occurs between
nonsister chromatids of homologous chromosomes
Darwin inferred that those organisms with traits best suited to environment tend to leave more _______ than other members of a population
offspring
A(n) ________ is a group of individuals of the same species living in the same area that interact with each other
population
in sexual selection, individuals with certain inherited characteristics are more likely to obtain mates than other individuals. This often results in ____________, differences between the sexes in size, appearance, and behavior
sexual dimorphism
Genetic variation in a population of animals or plants depends mainly on which of the following?
sexual reproduction
Organisms that possess homologous structures probably ___________
share a common ancestor that also had this structure
________ favors intermediate phenotypes, selecting against phenotypes at both ends of a range and reducing variation
stabilizing selection
If color is an inherited trait in beetles, and birds are more likely to eat brown beetles than green beetles,
the frequency of the green allele will increase
Genetic drift is a process based on
the role of chance
A mutation occurs when
there is a change in the DNA sequence of a gene
The first tetrapods (four-legged animals) were amphibians, which evolved from a specialized group of lobed-fin fish. An unusual fossilized animal (named Tiktaalik) was recently found; this animal possessed a mixture of fish and amphibian characteristics. What is the term used to describe such an intermediate organism?
transitional form
All of life is related through common ancestry, accounting for the ______ of life.
unity
How many different genotypes are in this rabbit population?
3
In a certain group of African people, 4% are born with sickle-cell disease, an autosomal recessive disorder. Heterozygous individuals not only don't have sickle-cell disease but also are resistant to malaria. If this group is in Hardy-Weinberg equilibrium, what percentage of the population is heterozygous and resistant to malaria?
32%
Environmental Change
A drought causes a habitat to turn dry and brown
Which of these individuals is a homozygous genotype?
AA
Suppose that every few years, all people over 6ft tall do not have any children. How will this affect the human population?
Alleles that promote "tallness: will decrease in frequency
What does Dr. Carroll mean when he says, "while mutation is random, natural selection is not"?
-Natural selection acts on traits -Natural selection favors some mutations -Mutations for advantageous traits are more likely to be passed on to the next generation
If a person has two normal copies of the hemoglobin allele, which statements are true?
-The person is homozygous at the hemoglobin locus -The person is susceptible to malaria
In the lab, Nachman examined dark mice from two different populations living hundreds of miles apart. The mice looked nearly identical. Their dark color was caused by two different genes. What does this tell you?
-Under very similar conditions, natural selection can favor very similar adaptations -Two completely different mutations in two separate genes can generate the same phenotype -There are at least two genes involved in creating dark mouse fur -Dark fur color evolved independently on each lava flow
Suppose that, with regards to a particular gene with two alleles, A and a, we know that 60% of the alleles in the gene pool of a particular large population are A. We observe this population for five generations, during which we know that no mutation, selection, or migration has occurred. After this period, the frequency of the a allele is expected to be _____
0.4
What is the allele frequency for the F allele in this population's gene pool?
0.7
Approximately one out of every 2,500 Caucasians in the United States is born with the recessive genetic disorder cystic fibrosis. According to the Hardy-Weinberg equilibrium equation, approximately how many people are carriers?
1 in 25
How many different fur color alleles are in this rabbit population?
2
How many different phenotypes are in this rabbit population?
2
In human gamete production there is an average of ________ crossover events per chromosome pair
2-3
HIV has become an important source of mortality for humans. If AIDS persists as a major factor for humans for many generations in the future, natural selection theory predicts that _____.
any heritable traits that help humans survive and reproduce in the presence of AIDS should become more frequent over time
