Chapter 5 Characteristics of Populations 5-1

1. Geographic Distribution: “range”, area inhabited by a population

2. Density: # of individuals per unit of area

3. Growth Rate: Increase, Decrease, or Stay the Same

Chapter 5 Characteristics of Populations 5-1

Patterns of organism distribution within a range:

1.Random: individuals are spaced in no apparent pattern

2.Uniform: individuals are spaced evenly

3.Clumped: individuals are distributed in small clumps or clusters

Population Growth• 3 Factors that affect population growth

– # of births (birth rate)– # of deaths (death rate)– # entering and # leaving

• Immigration: movement of individuals into an area (growth)

• Emigration: movement of individuals out of an area (decrease)

Exponential Growth• Exponential Growth: individuals

reproduce at a constant rate– Ideal conditions with unlimited

resources are necessary for exponential growth.

Logistic Growth

• Logistic Growth: when population growth slows or then stops - “S” curve (due to decreased availability of resources)

• Carrying Capacity: The largest number of individuals that an environment can support

5-2 Limits to Growth• Limiting Factor: Causes population growth to

decrease

1. Competition

2. Predation

3. Parasitism/Disease

4. Unusual Weather

5. Natural disasters

6. Human Disturbances

Density Dependent Factors• Density Dependent Limiting Factors – depends on

population size and density (number of organisms per unit area)

• Density dependent factors act most strongly when population is large and dense– Ex: Competition

– Ex: Predation

– Ex: Parasitism

Density-Independent Factors• Density –Independent Limiting Factors:

affect all populations, regardless of size– EX: weather, natural disaster, seasons, and

humans

5-3 Human Population Growth• Exponential human growth: for most human existence the

population grew slowly. Nat'l Geographic Pop Growth

• What limiting factors caused this? Death rate was high.

– ____________________

– ____________________

– ____________________

– ____________________

• Exponential growth: from the late 1700’s to the mid 1800’s the industrial revolution occurred.

• Human population growth exploded. Death rate was low.

– ____________________

– ____________________

– ____________________

– ____________________

• Demography: examines characteristics of human population and attempts to explain how populations will change over time.

• Tools used in demography:– Birth rate– Death rate– Age structure diagrams

• Demographic transition– 3 stages ( birth and death rate high, death rate begins to fall but birth rates stay high,

stage II birth rate falls to meet the death rate. (Unites States, Japan, and Europe)

Patterns of Human Population Growth

• Age structure diagrams: depicts the male and female members of each population by age range.

• Interpreting diagrams:– Pyramid – growing population

– Straight up and down (except older ages) – slow growth or stagnant

– Top heavy - declining population

Age Structure and Population Growth

6-3: Biodiversity• Biodiversity: sum total of genetically based

variety of all organisms

• Human threats to biodiversity:– Altering habitats– Hunting to extinction– Pollution– Introducing foreign species to new environments

Conserving Biodiversity• Conservation: wise management of natural

resources (preservation of habitats and wildlife)

• Ecological Hotspot: where habitats/species are in immediate danger of extinction

Why is biodiversity important?

• The greater the VARIATION in an ecosystem, the more likely it is to RECOVER if there is a disruption.– Increased diversity = healthier environment.

• Biodiversity is a resource– Most pharmaceutical drugs from plants.– Future food sources, building materials, etc…– “Beauty, fascination, & wonder”– Recreation (ecotourism).

• Threatened– Abundant in range, but decreasing in numbers.– At risk

• EndangeredBlack footed ferret

– Very few remaining in natural range– At risk for going extinct

• Extinct– Local extinction – gone from local range– Ecological extinction – gone from natural range (in

zoos only)– Biological extinction – gone from Earth forever.Endangered Species - Nature

1. Habitat Loss– “Hot spots” with greatest impact: tropical areas, coral reefs, wetlands,

grasslands, water (fresh & salt)

2. Invasive Species– Organisms not normally in habitat

3. Pollution– Air, water, soil impacts

4. Population– Arrival of humans and exponential population growth

5. Climate Change

6. Overexploitation– Ocean Fisheries

HIPPCO – Factors Leading to Species Extinction