BIOL 206 Exam 3 Study Guide

A set of practice flashcards covering population ecology concepts including dispersion patterns, metapopulations, demographic transitions, and survivorship curves based on the BIOL 206 Exam 3 study guide.

What is the definition of a population?

Groups of individuals, same species, same area, same time, that can reproduce with another.

What are the $3$ main types of dispersion patterns?

Clumped, uniform, and random.

What is the most common pattern and why

clumped cause it is the most common because resources are unevenly distributed.

Why is random dispersion the least common pattern?

It is the least common because nature rarely has perfectly even resources.

Provide an example of how dispersion patterns can change depending on the scale of observation.

Deer may appear clumped in one forest because they gather near water, but if you zoom into one meadow, they may appear more randomly distributed.

What is a metapopulation?

A group of separate populations of the same species connected by migration.

Why is migration a critical aspect of metapopulations?

Migration adds new individuals, increases genetic diversity, and can prevent populations from going extinct.

How is a source population defined?

A population that produces more individuals than it loses and sends individuals to other populations.

How is a sink population defined?

A population that loses more individuals than it produces and depends on immigrants to survive.

What information can be obtained from looking at the age structure of a population?

It shows the number of individuals in each age group and whether the population is likely to grow, stay stable, or decline.

What is the demographic transition?

The shift from high birth and death rates to low birth and death rates as a country develops.

What does a wide base on a graph of age structure predict for a population?

It means there are many young people, which predicts rapid future growth.

What is predicted for a population when its age structure graph is rectangular in shape?

The population is predicted to stay stable.

What does a narrow base on an age structure graph indicate about a population?

It means there are fewer young people and the population may shrink.

What characterizes a Type $I$ survivorship curve and what are some examples?

High survival when young and middle aged, with most dying when old; examples include humans and elephants.

What characterizes a Type $II$ survivorship curve and what are some examples?

There is an equal chance of dying at any age; examples include birds and squirrels.

What characterizes a Type $III$ survivorship curve and what are some examples?

A very high death rate when young, but survivors live much longer; examples include fish, oysters, and many plants.

What is occurring in the flat parts of a survivorship curve?

The flat part means that few individuals are dying.

What is occurring in the steep parts of a survivorship curve?

The steep part means that many individuals are dying quickly.

What factors would cause a survivorship curve to shift from Type $II$ to Type $I$?

Fewer predators, more food, more parental care, and better living conditions.

if survivorship is 0.776 at the age of three how much of the population survived?

77.6%

what four pieces of info are needed to predict how population should change from one time period to the next.

births deaths, immigration, and emigration n=births and immigrants minus deaths and emigration

if the per capita birth rate is 0.05 how many people should be born in a population of 100 people

5

how is per capita birth rate different from fecundity

• Per-capita birth rate: Average number of births per individual in the population per unit of time. (what actually happens)

• Fecundity: The maximum biological ability of an individual to produce offspring.(what could happen)

What is the intrinsic rate of increase (r or rmax)?

The intrinsic rate of increase (r or rmax) is the maximum possible population growth rate under ideal conditions, with unlimited resources and no limiting factors.

Why can the per-capita growth rate stay the same while actual population growth changes?

because population size changes. The rate stays the same, but more individuals are added because the population is larger.

Why aren’t there millions of elephants? Define carrying capacity.

resources are limited.

Carrying capacity (K): The maximum number of individuals an environment can support indefinitely.

What factor is missing from exponential growth models? Is it important?

Limited resources (competition/carrying capacity).

Yes. In real populations resources are limited, so exponential growth usually doesn’t last forever.

Define logistic growth.

Logistic growth is population growth that starts rapidly but slows as the population approaches carrying capacity (K).

It forms an S-shaped (sigmoid) curve.

If competition is included in logistic growth, why does the equation still contain r or rmax?

Because r (or rmax) is the population’s maximum growth rate.

In logistic growth, when is the population growth rate highest?

intermediate population sizes, about half of carrying capacity

Explain the parts of the logistic growth curve

Beginning Population is small Growth starts slowly.

Middle Growth is very fast. Plenty of resources remain.

Near carrying capacity Competition increases. Growth slows.

At carrying capacity (K) Births ≈ deaths. Population size stays about the same.

Why can carrying capacity differ between populations or over time?

Because environmental conditions change.

What does density dependent mean? What if birth and death rates were density independent?

Density dependent is Birth or death rates change as population density changes.

Example: More individuals → more competition → higher death rate.

Density independent: Birth and death rates do not depend on population size. They stay about the same regardless of density.

Examples of density dependent vs. density independent factors.

Dependent: Competition Predation Disease Parasites Limited food Limited space

Independent: Hurricanes Floods Fires Droughts Tornadoes Extreme temperatures

When would population growth increase as population size increases? What is this called?

When individuals benefit from having more members in the population. This is called the Allee effect.

What is the principle of allocation?

The principle of allocation states that organisms have limited energy, so energy used for one function cannot be used for another.

Compare r-selected vs. K-selected species.

• r = Rapid reproduction

• K = Kids get lots of care

Which are found in disturbed vs. stable environments? Why?

Disturbed environments: r-selected species. They reproduce quickly and colonize new habitats fast.

Stable environments: K-selected species. They compete well where resources are limited

Great tits: Why are clutches of 8–9 eggs most common if 11–13 survive best?

Because parents must balance current reproduction with future reproduction. 8–9 eggs maximize lifetime reproductive success

How do deer and conifer studies show the principle of allocation?

Deer that invest more in reproduction have less energy for survival. Conifers that produce many seeds often grow less.

More energy spent on one thing means less for another.

Why is parental care a trade-off between current and future reproduction?

Giving more parental care helps current offspring survive. However, it uses energy that could have been used to produce future offspring.

Define a community and an ecological niche.

Community: All populations of different species living in the same area.

Ecological niche: A species’ role in the ecosystem, including:

• Where it lives

• What it eats

• How it survives

• How it interacts with other species

Realized niche vs. fundamental niche.

Fundamental niche: Everything a species could use without competition.

Realized niche: What it actually uses after competition.

Superior vs. inferior competitors.

Superior competitor: Realized niche is close to its fundamental niche.

Inferior competitor: Realized niche is much smaller because competitors exclude it.

What is involved in one species outcompeting another?

A superior competitor is better at obtaining and using limited resources (food, water, space, light, nutrients).

How did Gause’s paramecium experiments show competitive exclusion and stable coexistence? Why is coexistence “lose-lose”?

Competitive exclusion: Two species using the exact same niche cannot coexist. One species eventually eliminates the other.

Stable coexistence: Species can coexist if they use different resources.

Why is coexistence “lose-lose”?

• Both species still compete.

• Each population is smaller than it would be if it lived alone.

interference and exploitative competition.

Interference competition: Direct interaction. Fighting, defending territory, blocking access.

Exploitative competition: Indirect. Individuals never meet. One species simply uses resources first.

How does resource partitioning lead to stable coexistence?

Species use different resources or use the same resource differently.

This reduces competition.

Their realized niches become different, allowing both species to survive together.

What causes niche shift (character displacement)? Is it sympatric or allopatric?

• Competition causes species to evolve different traits or use different resources.

It usually occurs in sympatric populations because the species live in the same area and interact.