AP Biology: Ecology Unit
Ecology: the study of how organisms interact with each other
Levels of Organization in Ecology:
Biosphere: the entire portion of the Earth occupied by life: basically the sum of all the planet’s
individual ecosystems
Ecosystem: All the living organisms in a given area along with the nonliving factors in which they
interact
Community: All the organisms living together and potentially interacting in a particular area
Population: A group of individuals all of the same species living in the same geographic area
The Biosphere:
Factors that affect the biosphere:
Abiotic:
Biotic:
Community Interactions:
A. Competition: No 2 species can exist in a community if they share the same niche!
Niche: a popluation’s role in a community; the total of its use of abiotic and biotic factors in the
habitat
Gause and the Competitive Exculsion Principle: his experiment showed that no 2 species
could exist together in the same community if they have the same niche
He said that if they do, then a few things will occur.
1) One species will be driven to extinction.
Picture of Gause’s Experiment:
2) Resource partitioning: evolve through natural selection to use different
resources
a. Example
Realized Niche vs. Fundamental Niche:
3) Character Displacement: Evolving of different traits to be better at
getting other resources
a. Example
B. Predation
Organisms have evolved to avoid it. How?
1) Plants with spines, thorns, chemical poisons
2) Animals
a. Have active defenses: hiding, fleeing (costly for energy)
b. Passive Defenses: camouflage and coloring
i)
Aposomatic: bright colors to show warning to others they are
poisonous
Example:
ii)
Batesian Mimicry: copycat coloration; a nonpoisonous animals has the
same coloration as a poisonous organism
Example:
3) Predation can maintain diversity in a community
a. If a dominant predator gets removed, the prey of this predator will increase in
numbers and outcompete other similar organisms for space or food.
b. This may cause the number of species in a community to drop.
c. Keystone Species: a species that exerts strong control on community structure
because of its ecological role or niche
Example 1: Sea Otters in the North Pacific
Example 2:
C. Symbiotic Relationships
1) Mutualism: when both species benefit from a relationship with eachotehr
Example:
2) Commensalism: when one species benefits from the other species is neither helped nor
harmed
Example:
3) Parasitism: when one species benefits and the other is harmed
Example:
D. Energy Transfers and the Food Chain and Food Web
E. Ecological Succession in a Community
1) Primary Succession:
2) Secondary Succession:
F. Cycles in Communities
1) The Carbon Cycle:
a. Cellular Respiration by animals and bacterial decomposers adds CO2 to atm
b. Photosynthesis removes CO2 from atm.
c. Burning fossil fuels adds CO2
d. Too much CO2 leads to global warming…..the gases are trapped around the Earth and
act like a blanket.
It is called a greenhouse gas because it absorbs molecules of heat and
slows its escape from Earth so the temps is getting hotter.
2) The Nitrogen Cycle
a. Nitrogen Fixation
b. Nitrification
c. Ammonification
d. Denitrification
3) The Water Cycle
a. Cellular Respiration puts water in atm.
b. Transpiration puts water in atm.
c. Evaporation from lakes, ponds, etc puts water in atm.
d. Condensation occurs in atm.
e. Water comes back to Earth from atm as precipitation.
4) The Phosphorus Cycle
a. Phosphorus is required for:
b. Weathering rocks gradually adds inorganic phosphates ions in the soil
c. Plants absorb this from the soil and build it into their organic compounds
d. Consumers eat the plants and assimilate organic compounds with P.
e. Excess phosphates in lakes and ponds can be a big problem!
Population Interactions:
A. Determining the Size of a population
B. Survivorship Curves
1) Type I:
a. Graph
2) Type II:
a. Graph
b. Characteristics
b. Characteristics
3) Type III
a. Graph
b. Characteristics
C. Age Structure Diagrams: diagrams that show if a population is growing, remaining stable, or
declining
1) Graph:
2) Graph
3) Graph
D. Population Growth
1) The biotic potential is the amount a population could increase if under ideal conditions.
It is affected by:
1) life span
2) age at which reproduction is possible
3) the number of times reproduction is possible
4) how many offspring can be produced
2) Graph of 2 major types of Population Growth
a. Exponential Growth
b. Logistic Growth
E. Limiting Factors
There are factors that will limit the size of a population.
1) Density Dependent Factors:
2) Density Independent Factors:
F. Populations will also exhibit Growth Patterns
1) R-strategists:
2) K-strategists