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parasitism mutualism predation herbivory
live their entire life within one host live their life within several hosts spend part of their life free-living spend their entire life free-living
As the frequency of resistant host individuals increases in the population, natural selection favors parasitic individuals with novel traits that allow them to escape host defenses. As the frequency of resistant host individuals remains unchanged in the population, natural selection favors parasitic individuals with novel traits that allow them to escape host defenses. As the frequency of resistant host individuals increases in the population, natural selection works against parasitic individuals with novel traits that allow them to escape host defenses. As the frequency of resistant host individuals decreases in the population, natural selection favors parasitic individuals with novel traits that allow them to escape host defenses.
This figure shows the life cycle of Plasmodium (the malaria parasite). What is being shown to occur at step 4? [Hint]
After meiosis, resulting cells develop into sporozoites and migrate to salivary glands. Sporozoites reproduce asexually to form merozoites in the human liver. Merozoites reproduce asexually until they cause red blood cells to rupture. Merozoites surviving the human immune system become male or female gametocytes.
In liver cells that are infected by Plasmodium, HLA-B53 proteins bind to a particular protein found in sporozoites. Snails infected with flukes become attracted to light, even though uninfected snails avoid sunlit areas and prefer shady environments. Flukes are known to use both snails and birds as host for different phases in their life cycle. When certain strains of Plasmodium are found together, the HLA-B53 proteins may not be able bind to a particular protein found in sporozoites.
Predators that selectively remove old and sick individuals will have a lower impact on the prey population. Researchers found that 66 percent of moose killed by wolves were of reproductive age. Predators that prey on the young and those of reproductive age are shown to have less of an impact on the prey population. A wolf control program in Alaska decreased the predator abundance to 55–80 percent below pre-control density. During this time period, the moose population tripled.
Prey availability determines the predator population size. Predation’s primary effect may be to lower the size of low-density populations. Predators regulate moose populations. Predation has little effect on moose populations.
that a caterpillar mimics the Mexican vine snake. that a species of fish hides in a hole until another fish swims past that it can attack and eat. that a species of fish takes the appearance of its surroundings. that moose are capable of killing or maiming wolves by kicking them.
Which of the following conclusions can be inferred by looking at the diagram of the experiment conducted by Leonard? [Hint]
Shell thickness remained the same in the presence of crabs and in the presence of broken shells. Shell thickness increased in the presence of crabs, but remained the same in the presence of broken shells. Shell thickness increased in the presence of crabs and in the presence of broken shells. Shell thickness remained the same in the presence of crabs and increased in the presence of broken shells.
that plant tissues could offer poor or incomplete nutrition. that plants could defend themselves effectively against attack. that herbivores could be kept in check by predation and disease. that herbivores prefer a variety of plants and thus do not overstress a species.
Observations of introduced populations of European rabbits showed little population growth and thus disprove the hypothesis. When observations regarding introduced species are combined with those from the control of moose and other herbivore predators, it shows that in some situations herbivory is limited in a top-down fashion. Observations of some escaped animals have shown that they can strip vast areas of land in the absence of natural predators or disease. That known examples used to support the hypothesis are unnatural situations and difficult to support.
The plant cell wall serves to prevent the herbivore digestive system from utilizing the available nutrients in the plant. Plants contain a low quantity of nitrogen. Since plants harvest sunlight, they are a poor source of energy. Plants remove toxic materials from the soil that bioaccumulate in their systems and adversely affect the health of herbivores that eat them.
Beetle larvae survive longer on cottonwood trees that have a higher concentration of defensive compounds. Beetle larvae survive less well on cottonwood trees that have a higher concentration of defensive compounds. Cottonwoods that have been browsed by beavers contain a higher concentration of defensive compounds. Cottonwoods that have been browsed by beavers contain a lower concentration of defensive compounds.
What observation can you make from the figure? [Hint]
In competition for seeds of the same size, species 1 will outcompete species 2 and drive it to extinction. Competition for the same size seeds will lead to the extinction of both species. Competition for the intermediate-size seeds will lead to the extinction of species 2. The competition between the two species for the intermediate-size seeds will drive one of them to extinction.
niche differentiation. fundamental niche. niche overlap. realized niche.
When the two competitors have slightly different fundamental niches, the poorer competitor can take refuge in areas that are beyond the better competitor’s tolerance. The principle of competitive exclusion allows species with the same niche to coexist. Competitors can coexist if some other factor reduces the population of the better competitor. In extreme cases, competition can lead to the complete exclusion of one species.
transportation of gametes to a new environment housing removal of the less-fit individuals of the species medical attention
Each participant receives an equal reward. Benefits change with time. Costs change with time. The net benefit of a mutualism can be measured for the individual by subtracting the costs of the interaction from the benefits, in terms of offspring production.
plants that produce a showy flower but no nectar plants that reduce their nectar production during adverse conditions bees pollinating flowers ants that create a garden where a species of fungi grows and serves as the food source for the colony
Why should the prey species be protected to begin with? Can predator control effectively reduce predation and allow populations to rebound? Do populations involved in predator control programs rebound as a direct result of the program or as a coincidence? Are predators responsible for the decline of some prey species?
