PopulationPopulation

Understanding populationsUnderstanding populations

The Human PopulationThe Human Population

BiodiversityBiodiversity

What is a population?What is a population?

Population – All the members of a species living in the Population – All the members of a species living in the same place at the same time. same place at the same time. EX: All of the bass in an Iowa lake make up one EX: All of the bass in an Iowa lake make up one

population. population.

Properties of PopulationsProperties of Populations

Density – the number of individuals in a Density – the number of individuals in a certain space certain space

Dispersion – is the relative distribution or Dispersion – is the relative distribution or arrangement of its individuals within a arrangement of its individuals within a given amount of spacegiven amount of space

Size- number of individualsSize- number of individuals Age distribution- proportions of Age distribution- proportions of

individuals of each ageindividuals of each age

What Limits Population What Limits Population Growth?Growth?

There are 4 variable that limit population There are 4 variable that limit population growth.growth. BirthsBirths DeathsDeaths ImmigrationImmigration EmigrationEmigration

A population gains individuals through births A population gains individuals through births and immigration and loses them by death and and immigration and loses them by death and emigration.emigration.

Population GrowthPopulation Growth

Growth Rate = The birth rate minus the Growth Rate = The birth rate minus the death rate.death rate.

Growth rate Births Deaths

A population will remain the same size if A population will remain the same size if the number of deaths are replaced by the the number of deaths are replaced by the same number of births.same number of births.

How Fast Can a Population How Fast Can a Population Grow?Grow?

Reproductive PotentialReproductive Potential: the maximum : the maximum number of offspring that each member of the number of offspring that each member of the population can produce.population can produce. Darwin calculated it would take elephants 750 years Darwin calculated it would take elephants 750 years

to produce 19 million descendants. Bacteria can do to produce 19 million descendants. Bacteria can do that in a few days.that in a few days.

Reproductive Potential cont.Reproductive Potential cont.

Increases when individuals produce more Increases when individuals produce more offspring at a time, reproducing more often and offspring at a time, reproducing more often and earlier in life. earlier in life.

Reproducing earlier shortens the generation Reproducing earlier shortens the generation time – the average time it takes a member of the time – the average time it takes a member of the population to reach the age when it reproduces. population to reach the age when it reproduces.

Typically smaller organisms have a smaller Typically smaller organisms have a smaller generation time than larger organisms.generation time than larger organisms.

How Fast Can a Population How Fast Can a Population Grow?Grow?

Exponential GrowthExponential Growth – – growth occurs faster growth occurs faster and faster. and faster. Occurs in populations Occurs in populations

when there is plenty when there is plenty of food, water and of food, water and space available and space available and little or no competition little or no competition or predatorsor predators

Environmental Limits on a Environmental Limits on a Exponential GrowthExponential Growth

Natural conditions are neither ideal or Natural conditions are neither ideal or constant, so populations don’t normally constant, so populations don’t normally continue to grow exponentially. continue to grow exponentially.

Only some members of a population will Only some members of a population will grow and reproduce, the properties of a grow and reproduce, the properties of a population may change over time.population may change over time.

Carrying Capacity (K)Carrying Capacity (K)

The carrying capacity (K) of an ecosystem for a The carrying capacity (K) of an ecosystem for a particular species is the maximum population that particular species is the maximum population that the ecosystem can support. the ecosystem can support. An ecosystem may go above this number but it An ecosystem may go above this number but it

will never stay there will never stay there

Resource LimitsResource Limits

When a population consumes a particular When a population consumes a particular resource at the same amount that the resource at the same amount that the ecosystem can produce the resource it ecosystem can produce the resource it limits the population. limits the population.

EX: plant growth is limited by water, sun EX: plant growth is limited by water, sun and mineralsand minerals

CompetitionCompetition

The members of a population use the The members of a population use the same resources in the same way so they same resources in the same way so they will eventually compete.will eventually compete. FoodFood TerritoryTerritory Social DominanceSocial Dominance LightLight Shelter Shelter WaterWater

Two types of population Two types of population regulationregulation

Density Dependent – Deaths occur more Density Dependent – Deaths occur more quickly when the population is more quickly when the population is more dense or greater in size.dense or greater in size.

Ex. Disease or pest infestationEx. Disease or pest infestation Density Independent – When a certain Density Independent – When a certain

portion of the population dies regardless portion of the population dies regardless of its size. of its size. Ex. Severe Weather or natural disastersEx. Severe Weather or natural disasters

How species Interact With How species Interact With Each OtherEach Other

What is the difference between lions at What is the difference between lions at the zoo versus lions in the wild?the zoo versus lions in the wild? Wild:Wild:

Lions are a part of a food webLions are a part of a food web Hunt zebrasHunt zebras Fight with hyenasFight with hyenas Fed upon by fleas and ticksFed upon by fleas and ticks

NicheNiche Niche – the unique Niche – the unique

role of a species role of a species within an ecosystem.within an ecosystem.

A Niche includes:A Niche includes: Physical homePhysical home The environmental The environmental

factors needed for factors needed for survivalsurvival

All of the interactions All of the interactions with other organisms.with other organisms.

Habitat vs. NicheHabitat vs. Niche

Habitat is where the organism livesHabitat is where the organism lives Niche is the patterns of use of its habitat. Niche is the patterns of use of its habitat.

Interactions between speciesInteractions between species

There are five major types of species There are five major types of species interaction. interaction. CompetitionCompetition PredationPredation ParasitismParasitism MutualismMutualism commensalismcommensalism

CompetitionCompetition

When different individuals attempt to use When different individuals attempt to use the same limited resources.the same limited resources.

Competition can occur within and between Competition can occur within and between speciesspecies

Competition occurs within the same Competition occurs within the same species because those organisms all have species because those organisms all have the same niche. the same niche.

When competition occurs between species When competition occurs between species we say that those species niches overlap. we say that those species niches overlap.

Adaptations to CompetitionAdaptations to Competition

When two species with niches that When two species with niches that overlap compete sometimes the better overlap compete sometimes the better adapted species survives and the other adapted species survives and the other does not. does not.

Competition can be reduced by niche Competition can be reduced by niche restrictionsrestrictions Using less of the areaUsing less of the area Using resources at different timesUsing resources at different times

PredationPredation

An organism that feeds on another An organism that feeds on another organism is a predatororganism is a predator

An organism that is fed on is preyAn organism that is fed on is prey

SymbiosisSymbiosis

Any relationship where two species live Any relationship where two species live in a close associationin a close association

Examples of Symbiosis: Examples of Symbiosis: ParasitismParasitism

An organism that lives in or on a host is a An organism that lives in or on a host is a parasiteparasite

Ex: ticks and dog heart wormEx: ticks and dog heart worm

Examples of Symbiosis: Examples of Symbiosis: MutualismMutualism

A close relationship where both species A close relationship where both species benefit each other.benefit each other.

Examples of Symbiosis: Examples of Symbiosis: CommensalismCommensalism

A relationship where one species A relationship where one species benefits and the other is neither harmed benefits and the other is neither harmed nor helpednor helped

CommensalismCommensalism

CoevolutionCoevolution

Over time, species in close association Over time, species in close association may (think symbiosis) coevolve.may (think symbiosis) coevolve.

These species may evolve together.These species may evolve together.