Populations Population- A group of organisms of the same species that live in a particular area. Three important characteristics of a population are

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 a constant rate.

Under ideal conditions with unlimited resources a population will grow exponentially.

Often call J shaped curve.


We do know that populations cannot grow exponentially for very long.

What cause a population to slow down or even stop? RESOURCES! As resources become less available,

the growth of a population slows or stops.

Logistic Growth occurs when a population growth slows or stops following a period of exponential growth.


Populations that illustrate logistic growth have reached their Carrying Capacity.

CC- The number of organisms a given ecosystem can support.

S-shaped curve

Carrying CapacityCarrying Capacity

Carrying CapacityCarrying Capacity

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

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

These factors operate most strongly when a population is large and dense.

Density Dependent FactorsDensity Dependent Factors

CompetitionPredationParasitismDiseaseCrowding

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 and certain human activities like damming of rivers and deforestation.

Human PopulationHuman Population




The human population has increased with time.

For most of human existence life was hard and limiting factors kept the population in check!

In fact only until recently….ONLY ½ of all children reached adulthood!

About 500 years ago the human population began to increase.

Growing Exponentially Industrial Revolution and Agriculture

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

Currently at 7 Billion People The population trends differ depending on

Developing and Developed Countries.


DEMOGRAPHYDEMOGRAPHY

Will our population continue to rise indefinitely? What is earth carrying capacity for humans?

Some scientist once believed that war, famine, and disease would be our limiting factors.

Do you agree?


DEMOGRAPHY- The study of population.Demography examines the characteristics of

human populations and attempts to explain how those populations will change over time!

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


Over the last centruy population growth in the US, Japan and much of Europe has slowed dramatically.

This hypothesis is referred to as DEMOGRAPHIC TRANSISITON- which is defined as a dramatic shift change between birth and death rates.


Throughout history, human societies have had both high birth rates and death rates.

With advances in medicine, nutrition, and sanitation, etc more children survive and reach old age. These changes lower the death rate and demographic transition begins.

For a brief time you have high birth rate but low death rates which causes your population to grow exponentially. (1770-1920 for the US)

As societies modernize, (raise their standard of living, better education) the birth rate will begin to fall, the population growth will slow.

The Demographic Transition is complete when birthrate falls to meet death rate and population growth stops.

Demographic TransitionDemographic Transition

Very few countries have actually completed DT; most places are still growing exponentially.

Much of the population growth today is contributed by only 10 countries .

Guess the top 10 Countries!!!!

http://www.mapsofworld.com/world-top-ten/world-top-ten-most-populated-countries-map.html This is NOT very accurate but still kind of neat!

http://www.internetworldstats.com/stats8.htm



The five stages of the demographic transition model1. Total population is low but it is balanced due to high birth rates and high death

rates.

2. Total population rises as death rates fall due to improvements in health care and sanitation. Birth rates remain high.

3. Total population is still rising rapidly. The gap between birth and death rates narrows due to the availability of contraception and fewer children being needed to work - due to the mechanisation of farming. The natural increase is high.

4. Total population is high, but it is balanced by a low birth rate and a low death rate. Birth control is widely available and there is a desire for smaller families.

5. Total population is high but going into decline due to an ageing population. There is a continued desire for smaller families, with people opting to have children later in life



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.

Total Population of the World by Decade, 1950–2050(historical and projected)

YearTotal world population

(mid-year figures)Ten-year growth

rate (%)

1950 2,556,000,053 18.9%

1960 3,039,451,023 22.0

1970 3,706,618,163 20.2

1980 4,453,831,714 18.5

1990 5,278,639,789 15.2

2000 6,082,966,429 12.6

20101 6,848,932,929 10.7

20201 7,584,821,144 8.7

20301 8,246,619,341 7.3

20401 8,850,045,889 5.6

20501 9,346,399,468 —

Total Population of the World by Decade, 1950–2050

(historical and projected)

http://www.youtube.com/watch?v=E8dkWQVFAoA

http://www.youtube.com/watch?v=s-57ui-r6Qw

http://www.youtube.com/watch?v=VcSX4ytEfcE

http://www.youtube.com/watch?v=iodJ0OOdgRg

Documents

Populations Population- A group of organisms of the same species that live in a particular area. Three important characteristics of a population are