Bio 004,CH18, College of the Desert
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Nonliving chemical and physical factors.
The basic unit of cological systems. Organismal ecology – pertains to the evolutionary adaptations that enable organisms to meet the challenges posed by their abiotic environments.
A group of individuals of the same species living in the same place at the same time. Population ecology – pertains mainly to factors that affect population density and growth.
Consists of all organisms that inhabit a particular area; assemblage of populations of different species. Community ecology – pertains to how interactions between species affect community structure and organization.
Includes all the biotic and abiotic factors within a specific area. Ecosystem ecology – pertains to energy flow and the cycling of chemicals among various biotic and abiotic factors.
The global ecosystem; the sum of all the planet’s ecosystems – all of the life and where it lives.
Abiotic Components of
- 1. Sunlight
- 2. Water
- 3. Temperature
- 4. Wind
- 5. Rocks and soil
- 6. Periodic Disturbances
Physiological response to a situation that is long term, but still reversible.
Acclimation that may become irreversible or reversible on a seasonal basis.
Acclimation that is a change based in behavior rather than a physical adaptation.
- Number of individuals of a species per unit area or volume.
- Dependent on: Size and behavior of species.
- a) Ant colonies - millions of individuals/acre
- b) One mountain lion/territory of 100 sq. mi.
Patterns of Dispersion
Way in which individuals spread out within a population’s geographic range.
Individuals aggregated in patches.
a) Most common in nature.
b) Associated with uneven nutrient distribution (fungi) or social behaviors (wolves).
Evenly spaced pattern of dispersion; direct result of individual interactions (gannets).
- Position of each individual is independent of other individuals.
- a) No strong attractions/repulsions
- b) Least common in nature
- c) Seeds (dandelions).
Zero population growth
Occurs when birth and death rates of a population are equal
Exponential population growth
Maximum increase of a species’ population under ideal conditions.
Maximum population size a particular environment can support.
Logistic population growth
Population increase levels off as carrying capacity is reached
Density Dependent Factor
Population-limiting factor whose effects intensify as population density increases. *Dwindling food supply *Buildup of toxic wastes *Decrease a population’s growth rate by increasing death rate, decreasing birth rate, or both.
Competition between individuals of the same species for the same limited resources. A s population size increases, competition for resources increases and growth rate declines in proportion to intensity of competition.
Density Independent Factor
Population-limiting factor whose intensity is unrelated to population density. Mainly affected by abiotic factors (aphids).
Snowshoe Hare and
Two species whose population size is directly dependent on the other.
The relative numbers of individuals at each age in a population.
Growth - 3 categories
- 1. Pre-reproductive juveniles
- 2. Reproductive adults
- 3. Post-reproductive adults
The series of events from birth through reproduction and death that affect an organism’s life schedule. Variable 1: At what age reproduction begins: Variable 2: How often reproduction occurs Variable 3: How many offspring are produced
A group of individuals of the same age whose fate can be followed from birth to death.
Plot of the proportion or numbers in a cohort still alive at each age.
- Type I: Low death rates during early and middle life, but steep death rates during late life. Few offspring with much care (humans).
- Type II: Constant death rates during the entire life of an organism. More offspring with some care (birds).
- Type III: High death rates during early life, but leveling off during middle and late life. Many offspring with little
- care (alligators).
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