Population Growth & Regulation

What happens under ideal demographic conditions?

Individuals experience a maximum intrinsic growth rate

What does the growth rate mean on a net basis?

How the population is changing

Why do populations grow slowly initially?

There is a small number of reproductive individuals

What does the growth rate increase with?

The number of reproductive individuals

What do most species have?

Discrete breeding seasons

How is the geometric growth model expressed?

Ratio of a population’s size in one year to its size in the preceding year

What is the population size when the geometric growth ratio is greater than 1?

The population size increased

What is the population size when the geometric growth ratio is less than 1?

The population size decreased

What happens when lambda < 1 and r < 0?

Population is decreasing

What happens when lambda = 1 and r = 0?

Population is constant

What happens when lambda > 1 and r > 0?

Population is increasing

How can the doubling time be estimated?

By rearranging the exponential growth model, and the rearranged equation then equals 2.

What is a factor that limits population size regardless of the population’s density?

Climactic events

What is the most common factor that causes negative density dependence?

Limiting resources

Why do limiting resources influence population density?

As a population’s size increases, resources are divided among more individuals, and per capita resources decline to a level at which individuals find it difficult to grow and reproduce

What can crowded populations lead to?

Generated stress

Transmitting diseases

Attraction to predators

What happens when plants are grown at high densities?

Each plant has access to fewer resources

What is often the slope of a self-thinning curve?

-3/2

What are the different characteristics of the logistic growth model?

Carry Capacity

S-Shaped Curve

Inflection Point

According to the logistic growth model, what happens as the population increases from a small size?

The rate of increase grows until reaching half of the carrying capacity, which corresponds to the inflection point

What happens once the inflection point is reached?

Individuals in the population continually decline in their ability to contribute to population growth

What do age structure pyramids with broad bases indicate?

A growing population

What do pyramids with narrow bases indicate?

A declining population

What do pyramids with straight sides indicate?

A stable population

What are the 3 types of survivorship curves?

Type 1
Type 2

Type 3

What does a type 1 survivorship curve depict?

A population that experiences low mortality early in life and high mortality later in life

What does a type 2 survivorship curve depict?

A population that experiences constant mortality throughout its life span

What does a type 3 survivorship curve depict?

A population with high mortality early in life and high survival later in life

What do most survivorship curves exhibit?

Combinations of features from type 1 and 3 curves

What are life tables typically based on?

The number of female offspring per female

When do stable age distributions occur?

When survival and fecundity of each age class stays constant over time

What is the survivorship in the fist age class always set to?

1

What assumption is being made when lambda or r is being estimated from a life table?

The life table has a stable age distribution

Why do age distributions fluctuate?

Due to environmental conditions

What are cohort life tables readily applied to?

Sessile organisms that can be traced over the course of their life

What can static life tables be applied to?

High motility organisms

Species with long life spans