1. Population Ecology
Ecology: study of the interactions of organisms with each other & with the physical environment
Population: all organisms of same species that live in a particular area
Community: all of the different populations in a given area
Ecosystem: all of the different populations in a given area including living (biotic) & nonliving
(abiotic) parts
Biosphere: portion of Earth’s surface where life exists

2. Patterns of Population Growth
Each population has particular patterns of growth
Population size can stay the same, increase or decrease according to per capita rate of increase (growth rate)
Biotic potential: Highest possible per capita rate of increase for a population

3. Patterns of Population Growth
Factors affecting biotic potential:
Average number of offspring per reproduction
Chances of survival until age of reproduction
Age at first reproduction
How often each individual reproduces
Population growth patterns can be exponential or logistic

4. Patterns of Population Growth
Exponential patterns of population growth result in a J-shaped curve because growth rate is increasing
Logistic growth patterns result in an S-shaped curve because environmental resistance

5. Patterns of Population Growth
Environmental resistance: all those environmental conditions that prevent populations from achieving their biotic potential
Limited food supply
Accumulation of waste products
Increased competition
Predation
Carrying capacity: number of individuals of a species that a particular environment can support

6. Survivorship Curves
Type I curve: individuals survive past midpoint & death comes near end of maximum life span
Type II curve: survivorship decreases at a constant rate throughout life span
Type III curve: most individuals die young

7. Human Population Growth
Growth in less developed countries is in exponential growth phase
Ex. Latin America, Africa, Asia
Population growth is expanding rapidly
Majority of people live in poverty
Growth in more developed countries has leveled off
Ex. North America, Europe
Population growth is low
Good standard of living

8. Human Population Growth
Suggestions to reduce population growth explosion in LDC (less developed countries):
Establish or strengthen family planning practices (birth control)
Reduce desire for large families
Provide education
Raise status of women
Reduce child mortality
Improve economic stability
Delay onset of childbearing

9. Age Distributions
Age-structure diagrams divide the population into three groups:
Preproductive
Reproductive
Postreproductive
LDC population continues to grow as long as there are more young women enter reproductive years than older women leaving them (unstable age structure).

10. Regulation of Population Growth
Factors that regulate population growth consist of two types of life history patterns:
Opportunistic patterns
Small individuals
Many offspring
Mature early
Short life span
Little or no care of offspring
Ex. Insects, weeds
Equilibrium patterns
Large individuals
Large populations
Slow to mature
A lot of care of offspring
Long lifespan
Ex. Birds, mammals

11. Regulation of Population Growth Cont.
Density-independent factors
Abiotic factors (weather, natural disasters)
Effects population all the same
Opportunistic life history pattern
Density dependent factors
Biotic factors (competition, predation, parasitism)
Effects depend on size of population
The more dense a population, the faster a disease might spread
Equilibrium life history pattern

12. Competition
Occurs when members of a different species try to utilize a resource that is in limited supply
Light, space, nutrients
Ecological niche: role organism plays in the community that includes its habitat & interactions with others
Habitat: where an organism lives
Competition exclusion principle: no two organisms can occupy the same niche at the same time when resources are limited
Resource partitioning reduces competition by dividing the feeding niches.

13. Predation Predation occurs when one organism feeds on another (prey)
Predator-prey cycling can occur if:
The predator population overkills the prey & forces a decline in predators.
The prey population has huge booms of population growth beyond their carrying capacity which results in a crash. Predator population declines due to lack of food.

14. Antipredator Defenses
Prey have evolved strategies to escape predation
Coevolution: two species adapting in response to selective pressure imposed by each other
Sharp spines of cacti
Pointed leaves of holly
Leathery leaves of oak tree
All discourage predation by insects
Prey escape predation by utilizing camouflage, poisonous secretions, fright, flocking together, warning coloration, and mimicry.

15. Mimicry
Occurs when one species resembles another species or an object in environment to escape predation
There are 2 types of mimicry:
Batesian mimicry: prey that is not harmful mimics another species that is harmful.
Ex. Flower fly & beetle will look like stinging wasp
2. Mullerian mimicry: both species that look alike have good defenses
Ex. Bumble bee & wasp

16. Symbiosis
Refers to close interactions between members of two different species
Three types of symbiotic relationships are:
Parasitism: (+) (-) the parasite gets nourishment from another organism called the host.
Ex. Leeches, ticks, tapeworms
Commensalism: (+) (0) one species benefits, the other species is neither harmed nor helped.
Ex. Barnacles on whales, clownfish/anenomes
3. Mutualism: (+) (+) both species in the association benefit.
Ex. Ants & bullhorn acacia tree, plants & animal pollinators