AP Environmental — Unit 3: Populations

Survivorship Curves

A line that shows the survival rate of a cohort: group of same/aged individuals from birth to death

Type I Survivorship Curve

• Early life

  • High survivorship due to high parental care

• Mid life

  • High survivorship due to large size and defensiveness

• Old age

  • Rapid decrease

Type II Survivorship Curve

• Steadily decreasing survivorship throughout life

• Whether young or old, equal survival rate

• Constant mortality rate

• Small rodents are a good example

Type III Survivorship Curve

• Early life

• High mortality due to little parental care

• Mid life

  • Few make it

  • Steady decline in survivorship

• Old age

  • Slow decline in survivorship

Carrying Capacity (k)

The max number of individuals in a population that an ecosystem can support based on limiting resources/factors

Overshoot

When a population temporarily exceeds the carrying capacity of its environment, meaning it is using resources faster than the environment can regenerate them

Die-Off

A sudden and drastic decrease in the population size of a species

Dieback

A gradual decline, where a population shrinks from its peak, but the individuals may not be entirely killed and could potentially recover if conditions improve

Density-Dependent Factors

Factors that influence population growth based on size

• Food

• Competition for habitat

• Water

• Light

• Diseases

• Large populations are more likely to be more largely impacted, especially when clumped

Density-Dependent Factors

Factors that influence population growth ithat’s not based on size

• Natural disasters, no matter how big or small a population is

Biotic Potential

• Exponential growth

• No limiting resources

• Limiting resources slow growth, eventually limiting

Environmental Resistance

• Logistic growth

• Initial rapid growth, then limiting factors limit the population to k