AP Biology : Understanding Biological Fitness

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Understanding Biological Fitness

There are two very different reproductive strategies in nature: r-selection and k-selection. These strategies are so extreme, we typically observe organisms somewhere in between these two strategies.

Which of the following characteristics is not indicative of r-selection?

Possible Answers:

Small brood size

Very little parental care

High brood mortality rate

Very fast maturation of organisms

Correct answer:

Small brood size

Explanation:

The r-selection strategy for reproduction is typically seen in environments that are very volatile and unpredicatable. It has a variety of characteristics including high brood sizes with a high mortality rate, and fast maturation with very little parental assistance. Low brood sizes are typically seen in the k-selection strategy for reproduction.

Example Question #45 : Natural Selection

Which characteristic is least likely to affect an organism's biological fitness in the tundra?

Possible Answers:

Nocturnal versus diurnal activity

Exothermic versus endothermic regulation

Size

Color

Fur

Correct answer:

Nocturnal versus diurnal activity

Explanation:

Biological fitness is directly related to the ability of an organism to survive and produce future progeny. There are a lot of factors that will play into an organism's fitness, especially in a harsh place like the tundra. Small size can be beneficial, as smaller animals require less food and can survive better in harsh environments, but large size can be beneficial to help preserve body heat. The color of an animal will help it to hide from predators; many tundra animals are white to help them blend in to the snow. Thermoregulation is extremely important in a cold environment; endotherms are able to regulate their own internal temperature, and will survive better than exotherms, which would be affected by the cold temperature of the air. Finally, fur and feathers help to trap body heat close to the skin and would enhance the fitness of animals in a cold environment.

Size, color, mode of thermoregulation, and fur all impact an animal's ability to survive in the tundra. Nocturnal activity, however, would not necessarily be favored over diurnal activity, as there is no clear advantage of one over the other in this specific environment.

Example Question #2 : Understanding Biological Fitness

In the evolutionary sense, which organism has the highest fitness?

Possible Answers:

A prairie dog that, though smaller than the average member of her species, has twice as many healthy young in each litter

A turtle that lays hundreds of eggs each nesting season, although an unusually small number of these eggs hatch successfully

A sterile mule that can pull over 800 pounds

A dog who cannot give birth due to a hip abnormality, but is healthy in all other respects

A childless human male who lives to be over one hundred years old

Correct answer:

A prairie dog that, though smaller than the average member of her species, has twice as many healthy young in each litter

Explanation:

With regard to evolution and natural selection, fitness refers only to the ability of an organism to contribute to the next generation of its species. In other words, if an organism has a large number of viable offspring, its fitness is high, regardless of other factors like strength, size, and longevity.

Of these answer choices, the only organism with an above-average number of healthy, surviving offspring is the prairie dog. The mule and the dog have below-average fitness because they cannot give birth. The turtle also has below-average fitness because it produces an unusually low number of healthy offspring. The human male has average to below-average fitness; certain traits made him choose not to produce offspring, though he may have been able to produce numerous offspring.

Example Question #3 : Understanding Biological Fitness

Humans regulate their internal body temperature within a very narrow range. This is an example of __________.

Possible Answers:

metabolism   

constancy

homeostasis

evolution

Correct answer:

homeostasis

Explanation:

Homeostasis is the tendency of the body to maintain stable, constant states. Homeostasis is often mediated by negative feedback systems, which prevent the measure from getting too high or too low. Regulation of body temperature within a narrow range would be an example of homeostatic regulation. Other examples include blood glucose concentration and blood calcium concentration.

Metabolism refers to the chemical processes of the body. These processes can help maintain homeostasis, but are not directly responsible for body regulation.

Example Question #4 : Understanding Biological Fitness

Which of the following would be considered innate behavior?

Possible Answers:

Decisions

Inflexible behavior

Courtship

Communicating

Classical conditioning

Correct answer:

Inflexible behavior

Explanation:

Innate behavior is known as inflexible behavior, in which learning plays no role in the behavior. Communicating, courtship, and decision making all rely on learned behavior from the environment. 

Example Question #1 : Understanding Biological Fitness

Which organism would be considered the most biologically fit?

Possible Answers:

Lives 94 years and produces 5 offspring

Lives 27 years and produces 1 offspring

Lives 70 years and produces no offspring

Lives 45 years and produces 3 offspring

Lives 36 years and produces 6 offspring

Correct answer:

Lives 36 years and produces 6 offspring

Explanation:

The most biologically fit organism is one that produces the most fertile offspring. Lifespan can correlate to the number of offspring produced, but is not a direct factor in determining fitness.

Since the organism that lives 36 years produced the most offspring (6), it is the most biologically fit.

Example Question #5 : Understanding Biological Fitness

In regard to the theory of evolution, “fitness” most likely refers to which of the following?

Possible Answers:

Reproductive success

All of these

Flexibility of an individual

Physical abilities of an individual

Correct answer:

Reproductive success

Explanation:

In evolutionary terms, “fitness” refers to the reproductive success or reproductive potential of an organism—its contribution to its species' gene pool.

Example Question #2 : Understanding Biological Fitness

A harmless species of butterfly mimics the coloration of a poisonous species. This is an example of which of the following?

Possible Answers:

Mullerian mimicry

Batesian mimicry

Aposematic coloration 

Cryptic coloration 

Communal camouflage 

Correct answer:

Batesian mimicry

Explanation:

Batesian mimicry involves a harmless species mimicking an unpalatable or harmful species, such as the butterfly in the example. Mullerian mimicry involves two unpalatable or harmful species resembling each other. This also helps predators learn which types of species to avoid. Cryptic coloration is more simply known as camouflage. Aposematic coloration is warning coloration, such as bright colors on poisonous tree frogs or venomous snakes. 

Example Question #7 : Understanding Biological Fitness

Darwin's Theory of evolution by natural selection is based on all of the following postulates except __________.

Possible Answers:

the survival and reproduction of individuals is not random

individuals within a population are variable

at least in part, variations among individuals are passed on from parents to offspring

the survival and reproduction of individuals is random

some individuals are more successful in surviving and reproduction than others

Correct answer:

the survival and reproduction of individuals is random

Explanation:

According to Darwin's theory, the survival and reproduction of individuals is not random. Survival and reproduction is tied to the variations among individuals. Those with the most favorable variations are more fit; therefore, they are naturally selected.

Example Question #8 : Understanding Biological Fitness

Which of the following must be true for natural selection to take place in a population?

Possible Answers:

Adaptation to different environmental niches

There must be sexual dimorphism in the population

The population must be in competition with another population

Phenotypic variation is based on differences in genotypes

Correct answer:

Phenotypic variation is based on differences in genotypes

Explanation:

In order for natural selection to take place, members of a population must have different biological fitnesses (a measure of how likely it is that an individual will pass on its genes through reproduction). Different biological fitnesses are a result of different phenotypes. Organisms with phenotypes better suited to their environments will have a higher fitness. 

Natural selection does not require sexual dimorphism or competition between populations. Adaptation to environmental niches can result from natural selection over time.

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