Unit 8 Ecology High Points

Unit 8: Ecology High Points

Abiotic Factors

• Definition: Environmental factors that are not living.
• Examples:
  • Temperature
  • Light
  • Water
  • Nutrients
  • Soil
  • Wind

Biotic Factors

• Definition: Environmental factors that are living or related to living things.
• Examples:
  • Bacteria
  • Protists
  • Fungi
  • Plants
  • Animals
  • Competition
  • Symbiosis

Survivorship Curves

• Definition: A graph showing the number or proportion of individuals surviving to each age for a species.
• Types:
  • Type I:
  • Survivors tend to live long lives with a high death rate in old age.
  • Examples: Large mammals (e.g., humans).
  • Type II:
  • Constant death rate regardless of age.
  • Examples: Lizards, hydra, small mammals.
  • Type III:
  • High mortality rates in young but survivors can live long.
  • Examples: Many insects, fish.

Life History Strategies

• Darwinian Fitness: Calculated by the number of offspring that survive to reproduce.

• Key Stages:

  • Birth
  • Weaning
  • Maturation
  • Death

• r-Selection:

  • Focus on high reproduction rates with low parental investment.
  • Characteristics:
  • Many offspring produced with little care.
  • High mortality, rapid growth.
  • Typical of animals in unstable environments (e.g., fish, insects).
  • Follows a Type III survivorship curve.

• K-Selection:

  • Focus on quality, fewer offspring, high parental care.
  • Characteristics:
  • Longer maturation periods, extensive parental investment.
  • Higher survival rates for offspring.
  • Typical of stable environments (e.g., elephants, whales).
  • Follows a Type I survivorship curve and logistic growth.

Regulation of Population Size

• Density-Dependent Factors:

  • Affect r-based growth differently as population density changes.
  • Examples:
  • Predation: High prey density attracts predators, regulates prey populations.
  • Disease: More easily spreads in dense populations.
  • Waste: Accumulates and affects population growth.
  • Intraspecific Competition: Competition for resources increases as densities rise.

• Density-Independent Factors:

  • Affects per capita growth regardless of population density.
  • Examples: Natural disasters, severe weather, pollution.

Interspecific Interactions

• Competition (-,-): Overlapping niches lead to resource competition.

  • Competitive Exclusion Principle: Two species with identical niches cannot coexist.
  • Resource Partitioning: Evolving to use different resources to reduce competition.

• Predation (+,-): One organism benefits while the other is harmed. Includes herbivory.

• Symbiosis: Long-term interaction between species.

  • Types:
  • Mutualism (+,+) - both benefit (e.g., fungi and plant roots).
  • Commensalism (+,0) - one benefits, other unaffected (e.g., bacteria on skin).
  • Parasitism (+,-) - one benefits at the other's expense (e.g., tapeworm in humans).

Cooperation and Kin Selection

• Cooperation improves survival and fitness; forms of cooperation include:
  • Presenting alarm calls in the face of danger despite personal risk (e.g., squirrels).
  • Cooperative breeding in some bird species (e.g., Florida scrub jay).

Foundation and Keystone Species

• Foundation Species: Modify environments (e.g., kelp forests, coral reefs).
• Keystone Species: Have large impacts on community structure; removal can collapse ecosystems.

Invasive Species

• Introduced species that can exploit new niches and outcompete natives.
  • Examples: Kudzu, Asian carp, pythons.

Ecological Succession

• Primary Succession: New land/new environments; pioneer species assist in soil formation.
• Secondary Succession: Recolonization of a previously occupied habitat after disturbance (e.g., wildfires).
  • Key Stages:
  1. Pioneer species (e.g., lichens, annual plants)
  2. Intermediate species (e.g., grasses, shrubs)
  3. Climax community (e.g., mature oak/hickory forests).

Food Chains and Trophic Levels

• Energy flow: Sun -> primary producers (grass) -> primary consumers (grasshoppers) -> secondary consumers (frogs) -> tertiary consumers (hawks).
• Trophic Levels:
  • Primary producers: Autotrophs
  • Primary consumers: Herbivores
  • Secondary consumers: Carnivores
  • Tertiary consumers: Apex predators

Energy vs. Matter in Ecosystems

• Idea: Matter is recycled within ecosystems, while energy flows through and exits ecosystems.