APES Unit 3: Populations

k-Selected Species

Animals that breed for ‘quality’

Lower offspring, higher parental care

Many reproductive events.

Long lifespan and slower sexual maturity.

Slow population growth rate. Low biotic potential (maximum reproductive rate)

• Most mammals (humans, elephants)

• Birds

Density dependent. Near, pop. near carrying capacity.

r-Selected Species

Animals that breed for ‘quantity’

More offspring, lower parental care.

May only have one reproductive event,

Short lifespan, quick sexual maturity.

High population growth rate. High biotic potential (maximum reproductive rate).

• Insects

• ish

• Plants

• Turtles

Density independent. Highly variable population dynamics.

Survivorship Curves

A line that displays the relative survival rates of a cohort in a population from birth to the maximum age reaches by any one cohort member.

• Faster drop in line - Quicker individual die-off

• Slower drop in line - Bigger average lifespan

Type I (mostly k-Selected Species)

1st line counting up, most mammals

• Early Life, Mid Life: high survivorship (high parental care, defensive w/ big size)

• Late Life: low survivorship (old age)

Type II (mix of k-Selected and r-Selected)

2nd line, linear- birds, rodents

• Throughout Life: steady decline (some parental care)

Type III (mostly r-Selected Species)

3rd line - insects, fish, plants

• Early Life, Mid Life: low survivorship (little/no parental care, steady decline)

• Late Life: low survivorship (old age)

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