Population density is the number of individuals of a species per unit of area or volume.
Correct Answer
True
True. Population size is the total count, while population density expresses that count relative to space, such as plants per square meter. Density matters because it affects competition for food and how easily individuals find mates.
Category: Population Measurement
Question 2
Smaller organisms generally live at lower population densities than larger organisms.
Correct Answer
False
False. Smaller organisms tend to be packed more densely than larger ones, because each individual needs less space and fewer resources. A meadow can hold thousands of insects per square meter but only a few large grazers.
Category: Population Measurement
Question 3
Schools of fish and herds of elephants are examples of a clumped dispersion pattern.
Correct Answer
True
True. In a clumped pattern, individuals gather in groups, often for protection, social behavior or because resources are patchy. Schools of fish and elephant herds are classic examples.
Category: Population Measurement
Question 4
A Type II survivorship curve shows mortality concentrated in old age.
Correct Answer
False
False. Mortality concentrated in old age is the Type I pattern seen in humans and most mammals. A Type II curve shows a roughly constant chance of dying at every age, which many bird populations approximate.
Category: Demography
Question 5
A population with a per capita growth rate, r, of zero is growing at its maximum possible rate.
Correct Answer
False
False. Because r equals the birth rate minus the death rate, an r of zero means births and deaths balance and the population shows zero growth. A positive r means the population is increasing, and a negative r means it is shrinking.
Category: Growth Models
Question 6
Natural populations often overshoot their carrying capacity and then fluctuate around it.
Correct Answer
True
True. Real populations rarely settle exactly at carrying capacity. When they overshoot, deaths exceed births and numbers fall back, so the population tends to rise and fall around that level, as harbor seals and wild sheep do.
Category: Growth Models
Question 7
Carrying capacity is the minimum population size that an environment can sustain.
Correct Answer
False
False. Carrying capacity, K, is the maximum population size a particular environment can sustain with its available resources. It can shift with seasons, weather, disturbances such as fire, and the buildup of wastes.
Category: Growth Models
Question 8
A forest fire that kills deer whether the herd is crowded or sparse acts as a density-independent factor.
Correct Answer
True
True. Density-independent factors such as fire, weather, natural disasters and pollution kill individuals regardless of how dense the population is. Each deer has about the same chance of surviving the fire in a large herd as in a small one.
Category: Population Regulation
Question 9
Competition among members of the same species weakens as population density increases.
Correct Answer
False
False. Intraspecific competition intensifies as density rises, because more individuals share the same limited food, space and mates. This growing competition is what slows growth in the logistic model as a population approaches carrying capacity.
Category: Population Regulation
Question 10
Life history traits such as age at first reproduction and number of offspring are shaped by natural selection.
Correct Answer
True
True. Like anatomy and behavior, life history traits are heritable characteristics that evolve under natural selection. They help determine how fast a population can grow and how it responds to its environment.
Category: Population Regulation
Question 11
Humans have raised the carrying capacity of Earth for their own species through agriculture, sanitation and medicines such as antibiotics.
Correct Answer
True
True. Farming and domesticated animals increased food supplies, while sanitation, antibiotics and vaccines reduced deaths from infectious disease. These advances removed limits that once held human numbers down.
Category: Human Population
Question 12
Aposematic coloration is bright warning coloration that signals to predators that an animal is toxic or distasteful.
Correct Answer
True
True. Aposematic coloration advertises a defense, as in the fire-bellied toad and the monarch caterpillar, which stores plant toxins. Predators learn to associate the bright pattern with a bad experience and avoid it.
Category: Species Interactions
Question 13
In Batesian mimicry, a harmful species evolves to resemble a harmless one.
Correct Answer
False
False. In Batesian mimicry, a harmless species resembles a harmful or distasteful one and gains protection from predators that avoid the model, as when a hoverfly resembles a stinging wasp.
Category: Species Interactions
Question 14
The long, sharp thorns of a honey locust tree are an example of a chemical defense against herbivores.
Correct Answer
False
False. Thorns are a mechanical defense, a physical structure that discourages animals from touching or eating the plant. Chemical defenses are toxins or distasteful compounds the organism produces.
Category: Species Interactions
Question 15
Digitalis, a compound made by foxglove plants, is an example of a chemical defense against herbivores.
Correct Answer
True
True. Foxglove produces toxic compounds, including digitalis, that can poison animals that eat the plant. In carefully controlled doses, digitalis is also used as a heart medication.
Category: Species Interactions
Question 16
In mutualism, one species benefits while the other is neither helped nor harmed.
Correct Answer
False
False. In mutualism, both species benefit, as termites and their wood-digesting gut protists do. A relationship in which one species benefits and the other is unaffected is commensalism.
Category: Species Interactions
Question 17
Species richness is generally highest near the equator and lowest near the poles.
Correct Answer
True
True. Species richness, the number of different species in an area, shows a strong latitude pattern, peaking in tropical regions and declining toward the poles.
Category: Community Structure
Question 18
Relative abundance is the total number of different species living in a community.
Correct Answer
False
False. The number of different species is species richness. Relative abundance describes how common each species is compared with the total number of individuals in the community.
Category: Community Structure
Question 19
Secondary succession occurs where a disturbance removed most of a community but left the soil in place.
Correct Answer
True
True. After events such as a wildfire, the soil and some organisms remain, so recovery begins from that base. Primary succession, by contrast, starts on new land with no soil, such as fresh lava.
Category: Community Structure
Question 20
Snowshoe hare and lynx populations rise and fall in cycles that last roughly 50 years.
Correct Answer
False
False. Long-term trapping records show that snowshoe hare and lynx populations cycle with a period of about 10 years, with lynx numbers trailing hare numbers by one to two years.
Category: Species Interactions