Unit 7 Concept 3 - Population Energy

Population

• A group of organisms of the same species living in the same place.

population density

• measures the number of individual organisms living in a defined space.  

population density is affected by…

• Birth (natality)

• Immigration

• Death (mortality)

• Emigration

survivorship curve

• a graphic representation of mortality (death) patterns.

  • Shows the number of individuals in a population that can be expected to survive to any specific age.

Survivorship curve type 1

• Late loss; heavy parental care; Ex. Humans

survival curve type 2

• Constant loss; mortality unaffected by age; Ex. Some birds, rodents

survival curve type 3

• Early loss; produce lots of offspring at once and many die right away; Ex. fish, mosquitoes

dispersion

• the spatial distribution of organisms in a population.  

dispersion could be…

• random

• uniform/even

• clumped

exponential population growth

• Population grows without limit

• Ex. Human population

logistic population growth

• Population grows quickly at first and then levels off

• Ex. Most natural populations (fish, rabbits, trees, etc.)

carrying capacity

the theoretical maximum population that a given environment could support. 

random dispersion

• not affected by external factors

even dispersion

• competition for resources

clumper dispersion is influenced by…

• environment

• geography

• resources

• interaction between organisms

limiting factors (environmental resistance)

•  Aspects of the environment that limit the size a population can reach.

• can be biotic (living) or abiotic (nonliving)

• can also be classified as density-dependent or density-independent.

density dependent factors

• bigger impact on more dense populations.

• can be triggered by an increase in population size, and thus crowding.

• ex: predation, disease, competition

density independent factors

• regulate population growth regardless of its size or density.

• Nearly all species in an ecosystem are affected equally

• Ex. Weather changes, pollution, natural disasters

density

measure of # of individual organisms living in a defined space

population density formula

population/space