Ecology Unit
Ecology = the study of the interactions between organisms and the living and nonliving components of
their environment
Levels of Organization
1) Biosphere = thin layer of Earth and atmosphere
2) Ecosystem = all organisms and nonliving components in a particular place
3) Community = all interacting organisms living in an area
- includes only living things
4) Population = all the members of a species that live in one place at one time
5) Organism = one of that species
Components of the Environment
1) Biotic Factors = living components
- ex) all the living things
2) Abiotic Factors = non-living components
- ex) temp, pH, oxygen [ ], amount of sunlight
- importance varies from environment to environment
These two factors create biodiversity = the assortment, or variety, of living things in an ecosystem
Key Theme in Ecology
No organism is isolated
- all organisms are interconnected
- nonliving components effect survival also
- one change can affect everything
Energy Transfer in an Ecosystem
- Biomass = all the energy in an ecosystem
- All starts with the sun
- Producers (autotrophs) = make own food
- Consumers (heterotrophs) = must consume food to get energy
- primary consumers – eat producers (= herbivores)
- secondary consumers – eat consumers (= carnivores)
- omnivores = eat producers and consumers
- Decomposers = break down dead organisms (= detritivores)
Food Chain = sequence that links organisms and feeding relationships
Food web = shows complex relationships of organisms in an ecosystem
- all the food chains put together
Trophic Level = represents an organism’s position in the transfer of energy
Energy Pyramid = a diagram that compares energy used at each trophic level
- as you increase up the pyramid
1) energy available decreases
- only about 10% of the energy from previous level is obtained
2) biomass decreases
3) number of organisms decreases
Habitat vs. Niche
Habitat = the area where an organism lives
Niche = the role the organism plays in the environment
Species Interactions
1) Predation= one organism captures and kills another organism
2) Parasitism = one organism (the parasite) feeds on another (the host)
- usually the host is not killed Why?
3) Mutualism = cooperative relationship in which both species derive some benefit
- most important is probably pollination
4) Commensalism = one species benefits and the other is not affected
Factors of Population Changes
1) Birth
2) Death
3) Emigration = movement into a population
4) Immigration = movement out of a population
- Carrying Capacity = the maximum number of individuals of a particular species that the environment
can normally and consistently support
- Population Crash = a dramatic decline in the size of a population
- numerous reasons for this
- Limiting Factor = the factor that has the greatest restraint on population growth
ex) competition (food, shelter, water), predation, disease, weather, natural disasters, human activities
Changing of an Ecosystem
Succession = the gradual change of an ecosystem
- this change usually causes the types of species that live there to change
Two Types
1) Primary Succession = formation of an ecosystem from an uninhabited area
- ex) bare rock, volcanic eruption
- pioneer species = first organism to live there
2) Secondary Succession = reestablishment of a damaged ecosystem
- ex) fires, floods, natural disasters