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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.
– ____________________
– ____________________
– ____________________
– ____________________
Patterns of Human Population Growth
•
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)
Age Structure and 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
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
• Endangered
Black 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
HIPPCO – Factors Leading to
Species Extinction
1. Habitat Loss
–
“Hot spots” with greatest impact: tropical areas, coral reefs, wetlands,
grasslands, water (fresh & salt)
2. Invasive Species
–
3.
Organisms not normally in habitat
Pollution
–
Air, water, soil impacts
4. Population
–
Arrival of humans and exponential population growth
5. Climate Change
6. Overexploitation
–
Ocean Fisheries