Ecology #3: Distribution and Abundance

Question 1

Abiotic Requirements

Answer 1

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

Question 2

Biotic Interactions

Answer 2

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

Question 3

Dispersal

Answer 3

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)

Question 4

Evolution

Answer 4

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

Question 5

Stochasticity

Answer 5

Stochasticity: Randomness w/ little explanation

Question 6

Potential Distribution vs Actual Distribution

Answer 6

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

Question 7

Limits of Distribution and Abundance

Answer 7

• Habitat Suitability
• Historical Factors
• Dispersal

Example:
- Restriction of shipworms to warmer waters
- Hemlock looper moths more active during summer