POPULATION and the ENVIRONMENT

Aerial census for African buffalo in the Serengeti of East Africa

What is a population?

Aerial census for African buffalo in the Serengeti of East Africa

A population is a group of organisms living in the same habitat that belong to the same species.

World Population Growth 1750-2000(in millions)

Population Growth

It should be clear that the population to the right is growing.

What are some factors that may cause a population of organisms to increase or decrease over time?

Numbers of organisms in a population can go up, down, or stay constant over time.

Factors such as:Food/water availability, predators, competition from other species,parasites, disease catastrophic events, Migration (Emigration and Immigration)Habitat depletion….No home : (

Limiting factors – any condition of the environment that limits the size of a population (food, shelter, predation, sunlight, oxygen etc)

The population below is growing in number. When a population is growing, it is said to be growing exponentially. When a population is growing exponentially, is the birth rate higher, lower, or equal to the death rate?

Exponential growth

Population Growth PatternsLogistical vs. Exponential

In a population growing exponentially, the birth rate is higher than the death rate.

Exponential growth “J curve”

Population Growth Patterns

Population Growth PatternsSome populations of organisms reach a plateau in their growth. This is called their carrying capacity. These populations are said to be growing with logistical growth.

“S curve”

carrying capacity

Carrying capacity – The number of organisms that can be supported by a particular ecosystem *within natural resource limits-without destroying it.

Population Growth Patterns1. What is the carrying capacity of the

population on the right?2. About how many days did it take for

the population to reach carrying capacity?

3. Which of the following is probably NOT a reason the population reached and maintained a plateau?a. limits in food supplyb. competition with other speciesc. competition for spaced. a major storm

Logistical vs. Exponential

Population Growth Patterns• What is the carrying capacity of the

population on the right? around 135 individuals

• About how many days did it take for the population to reach carrying capacity? about 80 days

• Which of the following is probably NOT a reason the population reached and maintained a plateau?a. limits in food supplyb. competition with other speciesc. competition for spaced. a major storm would probably not cause a population to maintain its size

Logistical vs. Exponential

Logistical vs. ExponentialBelow is a graph of human

population growth over the last 8000 years.

Logistical vs. Exponential

What are some factors that have caused the human population to skyrocket in the past 200 years?

Have humans demonstrated logistical or exponential growth?

Logistical vs. Exponential

What are some factors that have caused the human population to skyrocket in the past 200 years?

Increased technology to alter habitats (ie: skyscrapers), and medical advances (ie: antibiotics)

Humans have demonstrated exponential growth.

Living organisms have the

capability to produce

populations of unlimited size, but

the environment can support only a limited number of

individuals from each species.

NO

Overpopulation - the condition of having a population so dense as to cause environmental deterioration, an impaired quality of life, or a population crash

Populations are DynamicWhat does that mean?

What factors contribute to the changes in size and composition over time?

• Birth rate/Death rateUnited States 14.1/8.7 Australia 12.7/7.3 Iraq 34.2/6.0 Iran 17.5/5.4 Japan 10.0/8.5 Italy 8.9/10.1

Russia 9.7/13.9 • Life Expectancy

Human Overpopulation• Migration: Emigration/Immigration– The U.S. population is growing by about 2.5 million

people each year. Of that, immigration contributes over one million people to the U.S. population annually.

• Limited Resources (food, water, and living space)• Density Dependent Factors: related to the density

of the population. Examples?• Density Independent Factors: Not related to

population size. Examples?

• Density Dependent Factors: related to the density of the population. (disease, predation, competition)

• Density Independent Factors: Not related to population size (killing frost, severe blizzard, hurricane, etc)

Exponential Growth of Human Populationcauses??

Human Impact on the Environment

• Deforestation• Pollution– Water supply (fertilizers, pesticides, fungicides, acid rain),

depletion of ozone layer, global warming

Environment - US current issues: air pollution resulting in acid rain in both the US and Canada; the US is the largest single emitter of carbon dioxide from the burning of fossil fuels; water pollution from runoff of pesticides and fertilizers; limited natural fresh water resources in much of the western part of the country require careful management; desertification

~CIA.gov