Apparently prior to the appearance of HIV in human populations, some humans had a characteristic that pre-adapted them to survive upon exposure to the virus.
In a population of HIV viral particles, a small proportion are of a genetic type that they are not effected by the drug.
As soon as the human population became exposed to HIV, some individuals adapted to the situation.
That is probably just a sampling error.
Upon exposure to the drug, some viral particles adapt by mutation to a form that can thrive in the face of the drug.
The 2 share a gliding/flying ancestor and as the continents drifted apart. What are now distinct species followed their separate and independent evolutionary courses.
When humans immigrated to Australia some 9000 years ago, they introduced many species of animals, including the sugar glider which is the European cousin of the flying squirrel.
The flaps of skin which permit flying and gliding are homologous.
During their separate evolutionary history, they cam to occupy similar ecological niches and converged on adaptations that permit them to move about in similar ways.
Where coral snakes are present, the brown snakes lived for a longer time then when coral snakes are absent.
Overall, the fitness of king snakes and brown snakes is equal.
King snakes are more likely to avoid predatory attacks when coral snakes are not present.
Predators innately avoid coral snakes.
The bright coloration of snakes apparently makes them conspicuous to visually-orienting predators.
The bones in the penguin's paddles are homologous with the bones in the paddles of the whales, but the paddles themselves are not.
The bones in the penguin's paddles are homologous with the bones in the paddles of the whales; the paddles are likewise homologous.
The bones in the penguin's paddles are of a distinct evolutionary origin compared with the bones in paddles of the whales; the paddles similarly have an unrelated evolutionary history.
The bones in the penguin's paddles are of a distinct evolutionary origin compared with the bones in the paddles of the whales, but the paddles are homologous.
The adjustment made to the phenotypes of the trees are not heritable.
The manner in which they have been managed has resulted in the new species or races much like what has occurred with the selection for breeds of cats has occurred with the selection for breeds of cats
The genetic changes that have occurred, while resulting in interesting and attractive phenotypes, inadvertently have also been responsible for the evolution of varieties that are highly susceptible to pathogens.
The shape and size of the plants represents the result of artificial selection
The fossil record
Morphology and anatomy
While giving such a call can be risky, the risks are not substantial, otherwise the gene(s) underlying the behavior would be removed by natural selection from the population.
Giving such a call is risky; that is there can be a substantial cost associated with giving the warning call. The cost takes the form of a reduction in future opportunities to produce offspring. Therefore, one would predict that older individuals wil be more likely to utter such calls than younger ones.
Males are more likely to give the calls than females. this is because males are polygynous. Since they may have many females and young in their territories, they stand to profit more. Each female will only preotecting a small number of young but each male will be protecting a number of females and their collective young.
The feeding apparatus of the butterfly and the hummingbird.
The wings of a dragonfly and that of a bird.
The flagella of prokaryotes and eukaryotes.
The wings of a bird and the arms of an orangutan.
One hypothsis for the plant-insect resemblance is that the mantis gains some protection from detection by potential predators.
It is likely that the distant ancestors of this mantis species had a very different appearance.
One hypthesis for the plant-insect resemblance is that the mantis is difficult for orchid pollinators to see.
The orchid may have evolved to resemble the mantis in order to give the mantis protection from predators.
A bee or wasp visiting the orchid will most likely not be a "worker".
If you notice the phenotypically the mice in the western and eastern populations are the same, natural selection must not be occurring.
Since all of the mice currently on the island share a fusion of chromosomes 13 and 17, there must have been a single introduction in the 15th century. This could be the only explanation for all populations having that common feature.
If the western populations have been separated from the eastern ones for centuries, it is unlikely that mice from eastern populations will be able to mate (in the lab) successfully with mice from the western populations because natural selection will have favored different alleles in the 2 regions.
If the chromosome rearrangements have not disrupted the genes, then it is likely the changes can be attributed to genetic drift.
One must conclude that the mice were introduced on 2 separate occasions to the island-once on the east side and once on the side.
By "serving" themselves up to their mates in such a fashion, males may be reducing the likelihood that the females will mate with a second male and thereby dilute the effect of his sperm
By "serving" themselves up to their mates in such a fashion males may be reducing the size of their own population so as to recude competition among individuals for the limited amount of food available in their desert environment.
That male Australian red-backed spiders are sometimes eaten by their mates is beneficial to the males because by so doing, they fertilize more eggs than if they did not allow their mate to eat them.
The encouragement of the socially disadvantaged citizens to develop skills that would contribute to their social and political advancement.
The social integration of various "radical" and ethnic groups by promoting non-discriminatory policies.
Discouraging the reproduction of those deemed to be genetically inferious.
The demonstration of a philosophical bias by scientists that social behaviors were the consequences of environmental influences.
None of the above is a good answer.
That these various birds are all flightless can be most easily explained by convergent evolution.
Ancestors of these 4 kinds of ratites can be traced to the large land mass known as Gondwana that included what is now South America, Antarctica, Australia, New Zealand, and Africa.
Of the 4 groups of ratites, African ostriches are the most distinct because they have been isolated from other ratites for the longest period of time.
2 of the above are true.
A, B, and C are all true.
Humans evolved from chimpanzees.
Humans and chimpanzees share a relatively recent common ancestor.
Chimpanzees evolved from humans.
Convergent evolution led to the DNA similarities.
Lineages of organisms become more complex over time.
Evolutionary progress is slow and gradual.
Organisms evolve during their lifetime as they adapt to their environment.
If it would be adaptive for an species to have a particular characteristics, that characteristic will eventually evolve because of the random nature of mutations.
Organisms with an assemblage of characteristics that are the same probably have those characteristics because they descend from a common ancestor.
The gene(s) to mutate such that crickets will sing again.
That singing might become very common if the random sample contained one or more "singers"
There is less diversity in the mitochondrial DNA of finches on San Cristobal than among their finch ancestors remaining in the Americas.
There is more diversity in the mitochondrial DNA of finches on San Cristobal than among their finch ancestors remaining in the Americas.
There is the same level of diversity in the mitochondrial DNA of finches on San Cristobal as is found among their finch ancestors remaining in the Americas.
Birds had ancestors that were capable of swimming.
Whales had ancestors that were capable of flying.
Modern birds and whales share a common ancestor.
Modern flippers evolved from wings.
Modern wings evolved from flippers.
The theory has met with general acceptance because we have otherwise been unsuccessful in explaining the evolution of such complex structures as the human eye
The theory has not met with approval by evolutionary biologists because it has been demonstrated that there is no such intelligence that could be responsible for the organization of modern biological systems.
The theory is consistent with the theory set forth by Darwin and Wallace because an intelligence can only explain why evolution progressively leads to higher levels of complexity.
None of the above is a correct statement.
Demonstrating that life has existed on Earth for a substantially longer period of time than the BIble suggests
Promoting an approach to biology such that theories may be proposed without having first compiled an exhausted background of observations.
First proposing that the characteristics that organisms have can be inherited by their dominance.
First proposing that evolution occurs.
Since no one has observed evolution occurring, there is no reason to believe that it has ever happened.
Radiometric dating is not an accurate and reliable methodology for dating dead animals and plants.
Many structures are sufficiently complex that it is not possible that they evolve over some period of time because the earlier and simpler stages would not work properly and be adaptive.
One would expect that the frequency of Dx would remain at its elevated level.
One would expect that the frequency of Dx would continue to increase, as an adaptation to protect the viral popilation from possible introduction of another reverse transcriptase drug.
One would expect that the frequency of Dx would increase and Ds would decrease.
One would expect a complete loss of the Dx variety.
Birds with larger bodies had larger beaks and the larger-bodied birds were preferred by mates (sexual selection).
Birds with the larger bodies were more successful in avoiding predators and therefore had greater opportunities to reproduce.
A hurricane had caused a large-scale dying off the species, and by chance the few individuals that survived and then went on to reproduce, had beaks at the larger extreme of the previous generations (genetic drift)
A captive breeding programs initiated by the national park the oversees wildlife on the islands had unwittingly selected the largest and seemingly most robust individuals to breed. (Unknowing to the park rangers was that these individuals, despite their size, had low fertility, and the program was a disaster).
Larger-beaked individuals were more successful at harvesting the limited food resources available during the particularly arid period.
Gregor Mendel's model of particulate inheritance.
The modification (domestication) of populations of animals and plants by selective breeding
Populations must be relatively small (or at least not infinitely large).
There must be no migration.
Individuals must adapt to their environment.
There must be variation in the genetic make-up of individuals in a population.