Population Growth

What does the y-axis represent on a population size vs. time graph?

Population size (N).

What does the x-axis represent on a population size vs. time graph?

Time.

What type of curve represents exponential growth?

J-shaped curve.

What does a J-shaped curve indicate about resource availability?

Resources are unlimited.

What happens to growth rate as population increases in an exponential growth graph?

It increases continuously.

What equation corresponds to an exponential growth curve?

Nt = N0e^(rt).

How is time represented on a geometric growth graph?

Discrete intervals (e.g., years or generations).

What symbol is commonly used to represent geometric growth rate on a graph?

λ (lambda).

If λ > 1 on a graph, what happens to population size?

Population increases.

If λ = 1 on a graph, what happens to population size?

Population remains constant.

If λ < 1 on a graph, what happens to population size?

Population decreases.

What shape represents logistic growth?

S-shaped (sigmoidal) curve.

What does the upper horizontal asymptote represent in logistic growth?

Carrying capacity (K).

What happens to population growth rate as N approaches K?

Growth rate slows.

Where is population growth fastest on a logistic curve?

At intermediate population sizes.

What causes the curve to level off near carrying capacity?

Intraspecific competition and limited resources.

What does K stand for on a logistic growth graph?

Carrying capacity.

What does negative density dependence look like on a graph?

Growth rate decreases as population density increases.

How does competition appear graphically in density-dependent growth?

Reduced slope at higher densities.

What is shown by a self-thinning curve?

Inverse relationship between density and individual biomass.

What happens to plant size as density increases in a self-thinning diagram?

Individual size decreases.

What type of density dependence is shown when plants are smaller at high densities?

Negative density dependence.

What does positive density dependence look like on a graph?

Growth increases as density increases at low population sizes.

What ecological problem does positive density dependence illustrate?

Difficulty finding mates or pollinators.

What is an Allee effect?

Positive density dependence at low population sizes.

How is an Allee effect represented graphically?

Low growth at low density, increasing with population size.

What does the y-axis represent on survivorship curves?

Proportion surviving.

What does the x-axis represent on survivorship curves?

Age or life stage.

What does a Type I survivorship curve look like?

High survival early, steep drop late in life.

What organisms often show Type I survivorship?

Large mammals.

What does a Type II survivorship curve look like?

Constant slope across lifespan.

What organisms often show Type II survivorship?

Birds and some reptiles.

What does a Type III survivorship curve look like?

Steep early drop, then leveling off.

What organisms often show Type III survivorship?

Fish, plants, insects.

What does fecundity represent on a life table diagram?

Number of offspring produced.

Which life stage usually contributes most to population growth on a life table?

Adults with high survival and reproduction.

Why are life table diagrams more realistic than simple growth curves?

They include age structure and survival differences.

What is the key concept illustrated by all population growth diagrams?

Growth is constrained by limits and life history.