lecture #9: Population growth 1 & 2

Define population size.

The # of individuals of the same species living in a defined geographical area.

What is the equation for calculating population size change?

(Births — Deaths) + (Immigrants — Emigrants)

Geometric and exponential models describe population growth in what conditions?

In an idealized environment with unlimited resources and good conditions.

Logistic growth occurs in what conditions?

If there are limiting factors or limiting resources.

What is population growth rate?

The # of new individuals that are produced per unit of time minus the number of individuals that die.

What is intrinsic growth rate (r)?

The highest possible per capital growth rate for a population. Maximum reproductive rates und minimum death rates.

For a closed population (with no migration) what equation do we use?

r = b - d

r = birth rate (total # of births/ population #) - death rate (total # of deaths/ population #)

If we have a population of 100 bats and in a year 80 are born but 60 die, what is the intrinsic growth rate?

(80/100) - (60/100)

= (0.8) - (0.6)

= 0.2

0.2 individuals increase the population per year.

What is the equation to calculate exponential population growth?

G = r * N

# of individuals added (G)

= intrinsic growth rate (r) * pop. Size (N)

What 4 things happen due to density dependent control?

1. Intraspecific competition

2. Predation

3. Parasitism

4. Infectious disease

A higher population size means what?

Food supply diminishes and competition increases.

A higher density means what?

Infections disease spreads more easily and predictors are attracted.

What is density independent controls?

Limits population size regardless of the population’s density.

What are 6 examples of climatic events that are an example of density independent control?

1. Tornadoes

2. Floods

3. Extreme temperatures

4. Droughts

5. Fires

What does and does not change as density rises?

Birth and death rates do not change as density rises but suddenly mortality rate increases and reproductive rate decreases.

What type of correlation is there between population density and individual fitness?

Positive correlation

What is the logistic growth model?

The per capita rate of population growth approaches zero as the population size nears carrying capacity (K).

What is the equation for logistic growth?

G = (r*N) * ((K-N)/K)

G (the # of individuals added per unit of time)

= Growth rate (r) population # (N) * Carrying capacity (K) - population # (N) / Carrying capacity (K)

Define carrying capacity.

The maximum population size that can be supported by the environment.

What 3 things happen as the population size increases?

1. Resource shortages

2. Environmental limitations

3. Within-species competition

What is the inflection point on a graph?

The point on a sigmoidal growth curve at which the population has its highest growth rate.

What does a age structure pyramid with a broad base indicate?

A growing population

What does a age structure pyramid with a narrow base indicate?

A declining population

What does an age structure pyramid with straight sides indicate?

A stable population

What is a life table?

A take that contains class-specific survival and fecundity data. They are typically based on the # of female offspring per female.

What is a type I survivorship curve?

Low mortality early in life and high mortality later in life
(large mammals).

What is a type II survivorship curve?

Constant mortality throughout life span (different birds, squirrels, corals). Steady decline in survival throughout life.

What is a type III survivorship curve?

High mortality early in life and high survival later in life (weeds).

What is the net reproductive rate (R0)?

The total number of female offspring that we expect an average female to produce over the course of her life.

What is the equation for the net reproductive rate?

R0 = Σ(Lx * Bx)

Lx = survivorship

Bx = fecundity

Define survivorship.

The probability of surviving to any later age class (Lx).