BIOL 1070 Lecture Notes - Exponential Growth, Temperate Deciduous Forest, Allopatric Speciation

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October 5th 2011
Hypothesis: A proposed explanation for a fairly narrow set of phenomena usually based on prior
experience, scientific background knowledge, preliminary observations and logic.
To measure ecosystem diversity:
- To measure, we must define what organisms are sampled, the spatial area sampled, and
when/how long we sampled (time).
Species Richness: The number of species per specified collection/sample area OR specified
number of individuals.
October 17th 2011
What are the unique properties of a community?
- Number of species (diversity)
- Trophic structure (plants, herbivores, carnivores)
- Composition (abundance, evenness, dominance)
- (Richness, trophic level and abundance) d
What are the unique properties of a population?
- Size = number of individuals (abundance)
- Geographic distribution = area in which the individuals occur.
- Growth (increase or decrease in size)
- (Number of individuals (within species), area and growth)
What ecological factors place limits on a species’ geographic range?
- Abiotic factors
- Dispersal
- Biological interactions
- Habitat selection
What are abiotic factors?
- Climate (temperature, moisture)
- Soils (minerals, texture, acidity)
- Geology (rock type, land formations)
- Light (sun, shade)
- Nutrients (nitrogen, phosphorus, potassium)
- Habitat
- Pollutants
How do abiotic factors influence the distribution of plants and animals?
- Restrict access to resources
o Food/nutrients
o Habitat
- Limit physical tolerances
o Hot/cold
o Chemistry (toxins)
- Physical barriers
o River, mountain, lake and ocean
How would you determine which abiotic factor is limiting the distribution of a species?
- Field observation of actual range of distribution.
- Determine ecological tolerances.
- Correlation between environmental gradients and a species optimum range.
- Experiments (field transplant, controlled environment)
Which factor is most important? Light or water?
- Light is a critical factor in determining tree line.
October 19th 2011
The concepts of a niche
- A species has a range of tolerance to the environment
- Tolerance range defines suitable habitat (potential range)
A Niche consists of all the factors necessary for a species’ existence in terms of time, space, and
required resources.
Fundamental Niche: All the possible dimensions in which a species can survive in principle.
Realized Niche: The dimensions in which a species actually survives after the effects of biotic
Niche differentiation (realized niche) Natural selection for bigger and smaller beak sizes due to
competition for food.
Community Assemblage Development of ecological niche in a forest along a gradient of time.
An ecosystem engineer is any organism that creates or significantly modifies habitats.
A functional trait of alder shrubs is nitrogen fixation via a symbiotic relationship with nitrogen
fixing bacterium.
- Increased nitrogen allows colonization of spruce.
Are old growth forests important for maintaining biodiversity?
- Yes and No