Unit 3: Populations

Population

A group of organisms of the same species that inhabit a defined geographic area at the same time

Population Density

Number of individuals of a population that inhabits a certain unit of land or water area

Population / Area

Population Dispersion

How individuals of a population are spaced within a region

Uniform Dispersion

Dependent on the position of other members of the population

Random Dispersion

Independent of the position of other members of the population

Clumped Dispersion

Migration / dispersion in groups; most common

Biotic Potential

The amount that the population would grow if there were unlimted resources

Carrying Capacity

Variable K; maximum population size for the species that can be sustained by the environment

Exponential Population Growth

Unrestricted growth

dN/dt = rmax(N)

Logistic Population Growth

Restricted growth dictated by the carrying capacity

dN/dt = rmax(N)(K-N/K)

Overshoot

When a population exceeds its carrying capacity

Rule of 70

The time it takes in years for a population to double

70 / Growth rate in percent = Amount of years

Doubling Time

Amount of years for any variable to double

r-selected Organisms

Populations below the carrying capacity of their environment with high fecundity

Competition: Low

K-selected Organisms

Populations with growth limited by the carrying capacity and low fecundity

Competition: High

Survivorship Curves

The number of individuals in a population born at a given time that remain alive as time goes on

Cohort

Number of individuals in a population born at a given time

Type 1 Curve

K-selected; sharp increase of mortality at the end

Type 2 Curve

Mortality and survival rates are constant throughout time

Type 3 Curve

r-selected organisms; sharp increase of mortality near the start

Crude Birth Rate

Live births per 1,000 members of the population

Crude Death Rate

Deaths per 1,000 members of the population in a year

Actual Growth Rate

(birth rate - death rate) / 10

Population Change Over Time

(birth rate + immigration rate) - (death rate + emigration rate) / 10

Emigration

Movement of people out of a population

Immigration

Movement of people into a population

Total Fertility Rate (TFR)

The number of children a woman will bear during her lifetime

Replacement Birth Rate

The number of children a couple must have in order to replace themselves in a population

Infant Mortality Rate

The number of deaths of children under the age of 1 per 1,000 live births

Rapid Growth Age-Structure Pyramid / Diagram

Pre-reproductive >> Reproductive, Post-reproductive

Slow Growth Age-Structure Pyramid / Diagram

Pre-reproductive > Reproductive, Post-reproductive

Zero Growth Age-Structure Pyramid / Diagram

Pre-reproductive = Reproductive

Negative Growth Age-Structure Pyramid / Diagram

Pre-reproductive < Reproductive, Post-reproductive

Population Growth Rate (As Percent)

((B - D)/Number of people) * 100

Malthusian Catastrophe

The theory of overshooting the carrying capacity of the Earth resulting in a catastrophe

Macronutrients

Nutrients needed in large amounts

Micronutrients

Nutrients needed in smaller amounts

Hunger

Occurs when insufficient calories are taken in to replace those being expended

Malnutrition

Poor nutrition that results from an insufficient or poorly balanced diet

Undernourished

Those who do not receive sufficient resources

Food Deserts

Lack of access to fresh, healthy food

Niche

Total sum of a species’ use of the biotic and abiotic resources in its environment

Habitat

The area of environment where an organism or ecological community normally lives or occurs

Specialist

A species that has a narrow niche and can only live in a certain habitat

Generalist

A species that has a broad niche, is highly adaptable, and can live in varied habitats

Intraspecific Competition

Competition within a species

Interspecific Competition

Competition between species

Competitive Exclusion

When two different species in a region compete and one species wins due to better adaptation

Gause’s Principle

No two species can occupy the same niche at the same time and that the species that is less fit to live in the environment will relocate, die out, or occupy a smaller niche

Realized Niche

Occupation of a niche due to competition

Fundamental Niche

Occupation of a niche without competition

Resource Partitioning

When different species use slightly different parts of the habitat but rely on the same resources