Pre-Exam 2 Practice Activity

Huffaker’s mite experiment: What change best explains why spatial refuges allowed populations to persist?

Refuges decrease predation rate (p) by reducing encounters between predator and prey.

In a system where increased nutrients lead to rapid prey growth, why does total predation increase?

The increase in prey density (Nh) leads to more predator–prey encounters.

What is the difference between a species’ fundamental and realized niche?

A realized niche is where a species actually lives

A fundamental niche is where it could theoretically live.

Under what conditions were oscillations maintained in experimental studies of Lotka-Volterra predator-prey dynamics?

When refuges were provided and immigration was allowed.

What did the classic study of lynx and hare predator-prey dynamics demonstrate?

Hare population size is a result of its own growth minus the rate of predation by lynx.

Why do some species swarm (insects) or school (fish) in large numbers?

It is an adaptation to avoiding predation.

What happens to a population with an intrinsic growth rate (r) of less than 0?

The population will decline towards extinction.

List examples of density-dependent factors.

Predation, Competition, and Disease

(effects increase with population density).

Why do density-dependent factors become stronger when populations are crowded?

Because of more encounters, easier spread of disease, and more resource pressure.

List examples of density-independent factors.

Climate change, Natural disasters (hurricanes, fires), and Drought.

Definition: Density-independent factors

Factors that impact populations regardless of how many individuals are present.

Definition: Metapopulations

Multiple subpopulations connected by immigration and emigration.

What factors increase a species' vulnerability to extinction?

Small local population, narrow geographic range, and narrow habitat tolerance.

What factors decrease a species' vulnerability to extinction?

Large local population, extensive geographic range, and broad habitat tolerance.

What generally happens to the body size of individuals as population density increases?

The body size of individuals decreases.

In Connell's barnacle study, why were Balanus excluded from the upper intertidal zone?

High adult mortality due to desiccation (drying out).

What is the distribution pattern of desert creosote bushes when young vs. when mature?

Clumped when young; Regular when mature.

Survivorship Curve: Type I

Elephants/Humans; low juvenile mortality and mortality increases with age.

Survivorship Curve: Type II

Birds/Lizards; mortality is constant over time/across age.

Survivorship Curve: Type III

Fish/Plants/Insects; very high juvenile mortality rates; few reach adulthood.

What traits are expected for r-selected species vs. k-selected species?

r-selected: early age at maturation

k-selected: large body size.

Under what two conditions does a population grow?

Births > deaths (natural increase)

Immigration > emigration (net gain from movement).

What is the evolutionary trade-off found in crickets regarding wings and fecundity?

Long-winged crickets have lower fecundity

Short-winged crickets have higher fecundity.

Distribution Pattern: Regular

Individuals are evenly spaced due to competition.

Distribution Pattern: Random

Individuals are scattered unpredictably.

Distribution Pattern: Clumped

Individuals occur in groups due to resource availability.