1-10 Survivorship

APES 2024

Generalist

Generalist

large range of tolerance, broader niche (role) and food requirements

Generalists are less

prone to extinction

Generalists are more

likely to be invasive

When do generalists have an advantage

in changing conditions

Specialist

smaller range of tolerance, specific food requirements

Specialists are more

prone to extinction

Specialists have less

of an ability to adapt

Specialists have a

narrow ecological niche

Specialists have an advantage when

conditions are constant

Population growth rate (r) (intrinsic growth rate)

number of offspring an individual can produce in a given time period minus the deaths of individual or offspring during that same time period

Biotic potential

Every population has a maximum potential for growth when there is unlimited resources

K-selected species

low intrinsic growth rate that causes the population to increase slowly until it reaches carrying capacity

K-selected species tend to be

large, have few offspring per reproduction event, live in stable environments, expend significant energy for each offspring, mature after many years of extended youth and parental care, have long life spans/life expectancy, reproduce more than once in their lifetime

Competition for k-selected species is usually

high

R-selected species

high intrinsic growth rate, which often leads to population overshoots and die-offs

R-selected species tend to

Have many offspring and go over carrying capacity then dieback, be small, have many offspring, expend or invest minimal energy for each offspring, mature early, have short life spans, and may reproduce only once in their lifetime

Competition among r-selected species is

relatively low

K-selected species are typically more adversely affected by invasive species than

r-selected species which are minimally affected by invasive species

Most invasive species are

r-selected

Survivorship curve

A graph that represents the distinct patterns of species survival by cohort

Cohort

a group of individuals of the same age – in a population from birth to the maximum age reached by any one cohort member

How many survivorship curves are there

3

Type I survivorship curve

high survival throughout most of the life span, but then individuals start to die in large numbers as they approach old age

Type II survivorship curve

a relatively constant decline in survivorship throughout most of the life span

Type III survivorship curve

low survivorship early in life with few individuals reaching adulthood

K-selected species tend to exhibit

type I curves

r-selected species tend to exhibit

type III curves

Type I examples

elephants, whales, humans (usually K selected)

Type II examples

chipmunks, squirrels (r selected) raptors and birds of prey (K selected)

Type III examples

mosquitos, dandelions, many fish and frog species (r selected)