Drake University Bio 13 Exam 2

03/12/2025

Selection

The process by which certain traits become more or less common in a population due to the effects of environmental factors.

Non-random mating

Mating patterns in which individuals select partners based on specific characteristics, influencing genetic diversity.

Mutation

A change in the genetic sequence that can lead to new traits within a population.

Genetic drift

Random changes in allele frequencies within a population that can lead to divergence over time.

Migration

The movement of individuals into or out of a population, which typically does not cause divergence.

Biological species concept (BSC)

Defines species based on reproductive isolation and the ability to produce viable offspring.

Reproductive isolation

A condition that prevents different species from interbreeding and producing fertile offspring.

Phylogenetic species concept (PSC)

Identifies the smallest diagnosable monophyletic group and focuses on evolutionary relationships.

Speciation

The evolutionary process by which populations evolve to become distinct species.

Allopatric model

A model of speciation where populations are physically isolated from one another.

Vicariance

The physical splitting of a habitat leading to the separation of populations.

Sympatric model

A model of speciation that occurs within a shared habitat, often through strong selection.

Behavioral isolation

A form of reproductive isolation where differences in mating behaviors prevent interbreeding.

Competitive exclusion hypothesis

The principle that two species competing for the same resources cannot coexist.

Trophic cascade

A process in which a change in one trophic level can cause a cascading effect on other levels.

Keystone species

A species that has a disproportionately large effect on its environment relative to its abundance.

Population ecology

The study of how and why populations change in size and structure over time.

Exponential growth curve

A model of population growth where the growth rate becomes faster as the population grows.

Mass extinction

A significant decrease in biodiversity, typically defined by the loss of a large percentage of species within a relatively short period.

What is the criterion for defining species using the Biological Species Concept?

C. ability to interbreed and produce fertile offspring.

How many species of squirrels are represented by populations A, B, and C, if A can interbreed with C but not with B?

C. 3 species.

Which factors generally cause two populations to diverge genetically?

E. A, B, and C (genetic drift, mutation, sexual selection).

What is the most likely order of events in speciation scenarios?

B. barrier to gene flow, selection for different traits, distinct evolutionary lineages, two species.

What must occur for dispersal to a newly formed island to trigger speciation?

C. There is no movement back to the original island.

Which mechanism does not reinforce the divergence of two populations that have come into contact after diverging?

B. hybrid offspring have equal fitness, on average, to individuals from the parent populations.

How would you correctly modify the statement, 'One species evolves into another species'?

B. Divergence from a common ancestor results in two species.

What is the most important abiotic factor limiting the number of plants and animals in a given ecosystem globally?

C. year round availability of sunlight.

What defines a species’ niche?

E. All of the above (interactions with other species, sunlight, precipitation, temperature range, food requirements).

What does the competitive exclusion hypothesis predict?

A. Species with similar niches will partition resources.

Which of the following is not a reasonable explanation for why species do not occupy all available niche areas?

D. The abiotic factors of the unoccupied areas are different.

What type of reproductive isolation is represented by different courtship rituals among males of fruit flies?

C. Behavioral isolation.

Which of the following factors would not contribute to allopatric speciation?

E. Gene flow between the two populations is extensive.

Which biomes consistently have the greatest species diversity?

D. tropical forests and high mountains.

Would you expect a small island to have a high diversity of animals compared to a larger island?

C. No, because small islands are not as likely to be colonized.

What is the result of a new species of moth matching the bark coloration of a tree species?

E. Predation (due to co-evolution).

What type of interaction is represented by a bird eating in the mouth of a resting crocodile without being eaten?

C. Mutualism.

If a keystone species of small fish is removed from a pond, what would likely happen?

D. result in less algal growth, because of more zooplankton in the pond.

In a different pond close to the pond in #1, there are the same small fish, zooplankton, and algae. However, in this pond there are also many large predatory fish, resulting in very few of the small fish species. This pond also has very heavy algal growth. Which statement is supported by this information, and what you know from #1.

B. The small fish species is not a keystone species.

What does an increase in hawk numbers in a prairie represent?

C. Bottom-up control.

What would likely happen to the mouse population size if hawks are removed?

B. Exponential growth.

What does the per capita rate of increase for a population represent?

A. The difference between average number of births and average number of deaths in a year.

Which assumption is not true for a population under a logistic growth model?

E. All are true (per capita rate of increase changes, limited resources, individuals are added when the population is intermediate, modification of exponential growth model)

What is true if a population has a low density relative to its carrying capacity?

B. Birth rates and death rates will most likely not change with the addition of more individuals.

Which survivorship curve is typical of organisms with very high reproductive outputs?

C. III.

Why is the growing human population a concern for the global community of species?

E. All are true (substantial loss of major ecosystems, mass extinction event, loss of biodiversity, lose future medicines)

What is the number one threat to biodiversity?

C. Habitat loss.

What is the main goal of sustainable development?

B. Long-term prosperity of human societies without significant degradation of ecosystems.

Why do population ecologists follow the fate of same-age cohorts?

B. determine the birth and death rate of each group in a population.

What is true about a population’s carrying capacity?

A. may change as environmental conditions change.

According to the logistic growth equation, what is true when N equals K?

C. population growth is zero when N equals K.

During exponential growth, a population always:

B. grows at its maximum per capita rate.