BISC 130 - Chapter 20: Population Ecology

• Population Ecology

  • Important metrics

    1. Popoulation Size

       1. The number of individuals in a certain area

1. Popoulation Density

   • Size divided by area or volume

   • Varies depending on species

1. Distribution Patterns

   • Uniform, random, or clumped

   • Varies depending on species

1. Life Table

   • Show ages and mortality rates in these populations

   • Graphed as "Survivorship Curves"

     • Shape varies depending on species

• Organisms reproduce exponentially

  • Limited resources result in "logistic growth"

    • Rapid growth at first, then slows, and then levels out at carrying capacity (cc).

• The maximum number of organisms that an area or environment can support based on the resources available.

• Carrying capacity can change if environmental conditions change.

  • Ex: Change in available resources

  • Ex:  New competitors or predators

• Two main strategies toward growth and attaining cc.

  • K-selected species

    • Slow reproduction and growth

    • Few offspring

    • High parental care; takes 12 years for the parent to reach sexual maturity

    • Well suited to stable environments. Have a harder time adapting to change.

    • Ex: Elephants

• r-selected species

  • Rapid reproduction/growth

  • Many offspring

  • Low parental care

  • Suited to changing environments

  • Ex: Eastern Gray Squirrel

• Most populations in nature are at or near their carrying capacities at most times.

• Global human population existed at/near carrying capacities for thousands of years

  • Advances in technology and medicine have increased our carrying capacity

    • Its still growing today (global human population)

      • Varies depending on country - most growth in developing countries

• Carrying capacity of global human population:

  • Depends on desired quality of life

  • Depends on future advances in technology

Community Ecology:

• Predation: Predators kill and consume prey

  • Affects prey population size and carrying capacity

  • Prey availability affects predator population size and carrying capacity

• Herbivory: Herbivores eat plants

• Predation and herbivory create selective pressure on prey/plants to evolve defenses

  • Mechanical

  • Chemical

  • Camouflage

    • Used by predators too

• Aposematic Coloration

  • Bright/vibrant colors warn predators to avoid the organism

• Mullerian Mimicry

  • A type of mimicry where species share coloration and are all harmful to predators

• Competitive Excolusion Principle

  • Leads to extinction of one species in that community

  • Small differences can allow coexistence

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Symbiosis

• Predation is not symbiosis

• 3 types

  • Mutualism

    • Both parties benefit from the interaction

    • Ex: Clownfish and sea anemone; pollinators and flowering plants

  • Parasitism

    • One benefits, the other is harmed. Involves stealing resources over an extended period of time

  • Commensalism

    • One partner benefits, the other partner is neutral. Not helped or harmed.

    • Ex: Sharks and Remora

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