Ecology Exam 2
Amensalism
One individual is harmed, the other is unaffected.
Casual Encounters
Neither organism is harmed or benefits from interaction.
Competition/Defense
Both organisms are harmed.
Trophism
One organism benefits, the other is harmed.
Commensalism
One organism benefits, the other is unaffected.
Mutualism
Both organisms benefit.
Joseph Grinnell
Coined the word niche; an organism’s habitat.
Charles Elton
Redefined niche; an organism’s role in the environment.
G. Evelyn Hutchinson
Redefined niche; all physical and biological variables that affect organisms. Coined the term hypervolume.
Fundamental Niche
Conditions under which an organism can theoretically survive.
Realized Niche
Conditions where an organism actually does live.
Scramble Competition
Exploitative; siblicide in raptors and egrets.
Contest Competition
Interference; territoriality in songbirds.
Intraspecific Competition
Between individuals of the same species (males vs. females, adults vs. young, etc.).
Density Dependent Factor
Influence increases with increasing population density (disease).
Asymmetric Competition
One individual loses more than the other (most common in interspecific competition).
Symmetric Competition
Intense Competition.
Character Displacement
Natural selection favors changes that lessen competition.
Methods of Reducing Intraspecific Competition
Territoriality (birds), prolonged breeding season (frogs), dispersal of male or female offspring (cheetahs, African wild dogs).
Exponential Growth
Unchecked growth (humans, theoretical growth without environmental restrictions).
Logistic Growth
Exponential growth limited by carrying capacity (most organisms). Also known as sygmoidal growth.
Carrying Capacity (k)
Number of individuals capable of being supported by the environment.
Interspecific Competition
Between individuals of different species.
Competitive Exclusion
If resource requirements between individuals are similar, extinction or range shift occurs.
Niche Partitioning
Using different resources, in different areas, or at different times.
Allopatry
One species takes over entire ecosystem.
Competitive Release
Competing species are removed from an area, eliminating competition.
True Predators
Kill and eat another organism.
Parasitoids
Lay eggs on/in host, offspring consume host (Hymenoptera, Diptera). Sex of eggs can be controlled by parent.
Parasites
Predators that take nutrients from another organism. Usually live in several hosts throughout life, shouldn’t kill host.
Herbivores
Consume (but usually do not kill) vegetation.
Predator-Prey Relationships
Late 1800’s – focus on pest control, continued later as theoretical interest.
Components of Predation
Search, pursuit, handling times.
Hudson’s Bay Company
Fur trading company that recorded lynx/hare populations around Hudson’s Bay. Discovered population cycles (oscillations).
Gause (1934)
Studied effect of refuges, immigration, and emigration on predator prey relationships in microorganisms.
Huffaker (1958)
Studied effect of environmental complexity on predator-prey oscillations using mites and oranges.
Lotka and Volterra (1929)
Created equations to explain predator-prey oscillations.
Type I Functional Response
Proportion of prey consumed remains constant with increase in prey population.
Type II Functional Response
Proportion of prey consumed drops with increase in prey population.
Type III Functional Response
Proportion of prey consumed increases with increase in prey population, until a limit is reached and the proportion of prey consumed decreases.
Search Image
Ability to locate prey easily after a few trials.
Functional Responses
Eating at different prey densities.
Numerical Responses
Breeding at different prey densities.
Optimal Foraging Theory
Feeding as efficiently as possible given other constraints (what to eat and where to eat).
Specialists
Long search time, lots of calories.
Generalists
Short search time, less calories.
Prey Model (OFT)
Predator decides what to eat.
Patch Model (OFT)
Predator decides where to eat.
Time Minimizer
Minimizes time used to find food (hummingbird).
Energy Maximizer
Consumes as many calories as possible with no time constraints.
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