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.
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 four patients compare?
Each patient’s viral population would be unique, specifically adapted to deal with—and overcome—his or her unique immune system responses.
As proposed by Darwin, what sorts of traits are favored by natural selection?
Heritable traits that help individuals survive and reproduce more successfully than others in the same population.
Natural selection is best described as _____.
a filtering process that fine-tunes the traits of populations by sorting among existing, randomly produced variations
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
The evolution of populations due to chance is
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.
In a population with brown and green alleles for color, genetic drift
has more effect on the evolution of a small population.
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.
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.
A process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are individuals with other characteristics is called _____.
Which of the following is the study of the geographic distribution of species on Earth?
Which one of the following was an assumption of Charles Darwin’s theory of natural selection?
Populations produce more offspring than their environment can support
The population of American bison used to number in the millions of animals. Hunting and other problems greatly decreased the number of bison to about 1,000 animals. But today, the numbers are recovering to estimates of more than 200,000 animals. This crash in the population of bison and recent recovery is a good example of _____.
the bottleneck effect
Imagine that a new population of humans is established on a new planet from ten randomly selected people in your biology class. Over thousands of years, the descendants of those ten people reproduce and prosper, but do not reflect well the diversity of humans on Earth. This change in the diversity of people on the new planet is an example of _____.
the founder effect
The title of Darwin’s book in which he presented evidence that each living species descended from a succession of ancestral species is __________.
The Origin of Species by Means of Natural Selection.
What do we call scientists who study fossils?
There is a group of small fish living in a lake with a sandy bottom. Most of the fish are light brown, but about 10% are mottled. These fish are normally prey for large birds that live on the shore. A construction company dumps a load of gravel in the bottom of the lake, giving it a mottled appearance. Which of these statements presents the most accurate prediction?
The proportion of mottled fish will increase over time.
Which of the following is an example of natural selection that has been seen in our lifetime?
the evolution of antibiotic-resistant bacteria
Evolutionary biologists studying the evolution of lizard horn length found __________.
that lizard horn length evolved as a defense mechanism against predators
According to current evolutionary theory, which of the following is true?
Populations are the units of evolution
Which of the following events could NOT be caused by a population bottleneck?
Increased population size
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.
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.
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?
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?
In evolutionary terms, an organism’s Darwinian fitness is measured by its __________.
contribution to the gene pool of the next generation
The wing of a bat is homologous to the _____ of a whale.
Which of these individuals is a homozygous genotype?
All the genes in a population are that population’s _____.
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
Every few years a giant axe chops off the head of every person who is over 6 feet tall. How will this affect the human population?
Alleles that promote “tallness” will decrease in frequency.
Modern travel along with migration reduces the probability of _____ having an effect on the evolution of humans.
Homologous pairs of chromosomes are lined up independently of other such pairs during _____.
Crossing over, resulting in an increase in genetic variation, occurs between _____.
nonsister chromatids of homologous chromosomes
In human gamete production there is an average of _____ crossover events per chromosome pair
Click on the diagram to start the animation. Which of these gametes contain one or more recombinant chromosomes?
B, C, F, and G
Click on the diagram to start the animation. This animation illustrates _____ as it occurs during _____.
crossing over … prophase I
What process is illustrated by this animation?
Generation-to-generation change in the allele frequencies in a population is _____.
Where are the Solomon Islands located?
in the South Pacific
Scientists studying evolution on the Solomon Islands described which animal as the ‘poster child’ for the biological species concept?
Based on the video, what can you infer about speciation–the process by which one species splits into two or more species?
Physical separation of populations is often part of the speciation process
Why did the biologists consider a frog that they found to be a new species?