Populations

PopulationsPopulation- A group of organisms of

the same species that live in a particular area.

Three important characteristics of a population are its geographic distribution, density, and growth rate.

POPULATIONSPOPULATIONS

Population Growth- the change in the size of a population with time.

Population Density- is the number of individuals per unit area.

Geographic Density is how the population is distributed.

POPULATION SIZEPOPULATION SIZE

Three factors can affect population size.

Number of births Number of deaths Number of

organisms that enter or exit the population

POPULATION SIZEPOPULATION SIZE

Immigration- The movement of organisms into a population.

Emigration- The movement of organisms out of a population.

POPULATION GROWTHPOPULATION GROWTH

Exponential growth- occurs when the individuals in a population reproduce at an ever increasing rate.

POPULATION GROWTHPOPULATION GROWTH

Linear Growth-

increase of a population at a constant rate.

Maintaining a BalanceMaintaining a Balance

For a population to survive, a balance must exist between producers/consumers, predator/prey, growth and decay, water use and rainfall…etc.

Limiting FactorsLimiting Factors

Limiting Factors- Any condition of the environment that limits the size of a population.

Some can happen naturally and some are caused by humans.

Ex: Food, water, shelter and space availability, Predation, Climate, Disease, Pollution, Competition,….

HUMAN IMPACTHUMAN IMPACT

Humans have disrupted this balance through….

Building of roads, industry, homes

PollutionHunting/poachingGlobal Warming,

Excess CO2

Carrying CapacityCarrying Capacity

The number of organisms a given ecosystem can support.

S-shaped curve

Predicting Carrying CapacityPredicting Carrying Capacity

Because ecosystems change, carrying capacity is difficult to predict and calculate

However, islands are the ideal place to study (clear boundaries)

Rabbits in AustraliaRabbits in Australia

no rabbits in native ecosystems of Australia introduced in 1859 number increased rapidly plenty of vegetation;

no predators; no competition disease and starvation caused the rabbit pop. to

crash over time, vegetation recovered and rabbit pop.

increased again continues to increase and decrease, but less

dramatically

Rabbits reduced Phillip Island to a wasteland. Photos: Department of the Environment and Heritage

Recovery was spectacular after the rabbits were eradicatedPhotos: Department of the Environment and Heritage

Reindeer near Alaska 25 reindeer introduced to one of

Pribilof Islands near Alaska in 1911by 1938, herd had grown to 2,000reindeer ate mostly lichens, which

grow back very slowlyby 1950, only 8 reindeer alive on the

island

Predator/PreyPredator/Prey

This is an example of a predator/prey relationship.

As one increases the other will as a result decrease.….which in turns causes the other to decrease.

A normal cycle

Two Types of Population Two Types of Population

RegulationRegulation

Cause of death may be density dependent or density independent

Density Dependent Density Dependent FactorsFactors

Density Dependent Factors have an increasing effect as populations increases

deaths are caused due to density (population too many)

Density Dependent FactorsDensity Dependent Factors

Competition,PredationParasitismDiseaseCrowding

Population is growing rapidly and there are limited resources, predation,

or disease

Density Independent FactorsDensity Independent Factors

Density Independent Factors are factors that affect a population or cause death regardless of density.

Severe weather, natural disasters, etc. cause death that did not result due to density.

DEMOGRAPHYDEMOGRAPHY

DEMOGRAPHY- The study of population.

You can study charts of the age structure of a population and determine if it is growing or not.

Human PopulationHuman Population

HUMAN POPULATIONHUMAN POPULATION

Currently at 6.5 Billion PeopleGrowing ExponentiallyIndustrial Revolution and Agriculture

advancements are the reason for the drastic increase since the 1800’s

The population trends differ depending on Developing and Developed Countries.

Developed CountriesDeveloped Countries

Higher Average IncomesSlower Population GrowthDiverse Industrial EconomiesStronger social supportUses a large % of available resourcesEx: US, Canada, Japan, and countries of

Western Europe

Developing CountriesDeveloping Countries

Lower Average IncomesSimpler and agriculture-based economiesRapid Population GrowthUses small % of available resourcesEx: Indonesia and

countries in Africa.