CHAPTER 5

Populations

What is a population?

A population is a group of ONE kind of organism.

Examples: Herd of cattle Pack of geese

Population Density

Population Density describes how many individuals live in a given area.

Formula Pop. Den. = # Individuals

Area

Population Density Word Problems

• Example 1:– There are 60 flowers in a garden that is 3 feet by 4

feet. What is the population density per square foot?

• Example 2:– Given that the population density of a neighborhood is

10 people per square mile, how many people would live in a city with an area of 10 square miles?

Population Growth

Populations can change in size for any of the following reasons: Reproduction Death Immigration = moves TO location Emigration = moves AWAY from location Other Circumstances

Exponential Growth Curve

• When organisms reproduce very quickly, and there seems to be NO limits on population growth, the graph is said to be exponential.

• Sometimes this is called a J-curve because it looks like a J.

Logistic Growth Curve

• When organisms reproduce very quickly, and there seems to be limits on population growth, the graph is said to be logistic.

• Sometimes this is called an S-curve because it looks like a sideways S.

Logistic Growth (cont)

• The level that the graph plateaus at is called the carrying capacity.

• Carrying capacity describes the maximum number of individuals the environment can sustain given limited resources / factors.

Density-Independent Factors

Density-Independent Factors are factors that affect all populations in similar ways.

Examples: Weather / Seasonal Cycles Natural Disasters Human Activities

Density-Dependent Factors

Density-Dependent Factors usually affect populations with high population densities.

Examples: Competition Predation Disease Parasitism

Are these density-independent or density-dependent?

• Example 1:– A flu outbreak is spreading through a

large high school. Over 200 students become ill.

• Example 2:– A tornado funnel touches down in a

small farming community. The tornado destroys a third of the homes and businesses.

• Example 3:– Several lions and hyenas gather near a

small watering hole. There is limited water, so the lions and hyenas fight each other.

Human Population Growth

• Human population growth increased very slowly until the Industrial Revolution in the 1800s.

• It has since skyrocketed to over 7 billion people on Earth.

Patterns of Human Population Growth

Demography is the study of human populations.

Birth rate is the number of births per 1000 people.

Death rate is the number of deaths per 1000 people.

Demographic Transition

Stage 1 = High birth and death rates

Stage 2 = High birth rate, slowing death rate

Demographic Transition

Stage 3 = Slowing birth rate, low death rate

Stage 4 = Low birth and death rates

Age-Structure Diagrams

Age-structure diagrams (aka p0pulation pyramids) are modified histograms (bar graphs) that display the subgroups of a country based off of gender and age group.

The youngest individuals are on the bottom, and the oldest individuals are on the top.

Males are on the left, and females are on the right.

Age-Structure Diagrams

Depending on how well-developed a country is, the age-structure pyramid may have a different shape. Rapidly growing countries (developing) have a

very triangularly shaped pyramid with a very side base and narrow top.

Slowly growing countries (moderately developing) have a triangular shape, but the bottom is not as wide and the top is wider.

Negatively growing countries (well developed) have a small base and may seem almost uniform throughout the pyramid

Age-Structure Diagrams

CHAPTER 6

Human Impact on the Environment

Human Activities throughout History

Hunter-Gatherers

Agriculture

Industrial Growth & Urban Development

Biodiversity

Biodiversity describes the range of differences in living things in terms of ecosystems, species, and genetics.

Renewable resources are materials that can be reused and replenished whereas nonrenewable resources cannot.

Extinction & EndangermentExtinction & Endangerment Habitat FragmentationHabitat Fragmentation

Threats to Biodiversity & Natural Resources

Invasive SpeciesInvasive Species Soil ErosionSoil Erosion

Threats to Biodiversity & Natural Resources

DesertificationDesertification Pollution & Biological MagnificationPollution & Biological Magnification

Threats to Biodiversity & Natural Resources

DeforestationDeforestation OverfishingOverfishing

Threats to Biodiversity & Natural Resources

Controlled AquacultureControlled Aquaculture Air Pollution (smog, acid rain, etc)Air Pollution (smog, acid rain, etc)

Threats to Biodiversity & Natural Resources

Ozone DepletionOzone Depletion Global WarmingGlobal Warming

Threats to Biodiversity & Natural Resources

Current Solutions

Conservation efforts are underway to preserve ecosystems as they currently are.

Many businesses and governments are seeking ecological sustainability, meaning they will function in a way that will be able to help the environment while they run efficiently.