Ecology #3: Distribution and Abundance

Abiotic Factor: Non-living part of ecosystem that shapes species’ environment Example: - Temperature - Soil Type - Air Pressure - Precipitation - Humidity - Nutrients Availability - Sunlight Example: Western Hemlock Distribution and Abundance - Western hemlock looper moths eat hemlock (severe forest damage) - Moth outbreaks when higher temp and lower precipitation Note: Some super warm/dry times no moth outbreaks may be b/c… - Hemlocks still recovering from last outbreak - Third predator involved like birds - Trees gain immunity that slowly decreases before next outbreak

Biotic Interactions: Relationship between organisms Example: - Competition: 2 or more species/individuals compete for same limited resources (food, space, mates) • Parasitism: 1 parasite benefits by living on/inside host • Predation: 1 predator hunts, kills, and consumes prey • Commensalism: 1 species benefits while other neither helped/harmed • Amensalism: 1 organism harmed/inhibited while other remains unaffected • Mutualism: Both species benefit Example: Western Hemlock Distribution and Abundance - Western hemlock looper moths eat hemlock (severe forest damage) - Some super warm/dry times no moth outbreaks b/c third predator involved like birds

Dispersal: Movement of individual(s) away from their birth population to another location/population to settle and reproduce Example: Tough to disperse western hemlock seeds long distances; seed dispersal distance/conditions (wind, rivers, mountains)

Evolution: Genetic change in species/populations over time in response to ecological factors Example: Resistance to damaging factors; Western Hemlock Distribution and Abundance - Some super warm/dry times no moth outbreaks b/c trees gain immunity that slowly decreases before next outbreak

Stochasticity: Randomness w/ little explanation

Actual Distribution: Different from Potential Distribution b/c of interactions w/ other organisms (ex. competition) that may constrain geographic range Note: Optimum at peak of Physiological Process Rate vs Environmental Variable graph Note: If value of environmental variable falls outside species’ physiological tolerance range, species cannot survive there

• Habitat Suitability • Historical Factors • Dispersal Example: - Restriction of shipworms to warmer waters - Hemlock looper moths more active during summer