Unit 3

all Generalists and Specialists

• organisms are categorized into 2 groups:

  • generalists: species that can live in a wide range of environments and temperatures AND can utilize a wide range of resources (food for diet)

    • ex: Humans

    • Cope better to environmental changes because they can adapt and also can rely on a variety of resources

  • specialists: opposite of generalists—can only survive within a narrow range of parameters

    • Ex: animals that feed on one particular thing (Koala bear—can only eat eucalyptus leaves)

    • specialized ecological niche

    • Susceptible to changes like climate change

    • Can compete better than generalists in their particular habitat (they are highly adapted to their niche) - as long as the surrounding habitat remains constant

  • Racoon vs Red Panda: similar look and closely related

    • Red panda: specialist species—has a very narrow range of tolerance because it needs a specific habitat and food source (bamboo)

      • need to eat large amounts of bamboo because of low cellulose digestion

    • Raccoon: generalist species—has an extremely varied diet

      • Raccoons can eat plants, mushrooms, eggs (birds and reptiles), small insects and amphibians

      • far more adaptable

• Ecological tolerance:

  • specialists have a smaller range of tolerance, making them more prone to extinction—disturbed by invasive species

  • generalists have a larger range of tolerance, are less likely to go extinct, and are more likely to be invasive species. Very competitive.

K-selected and R-selected species

• K selected: Quality over quantity—have only a few offspring at a time but take their time raising them and take good care of their offspring TYPE 1

  • this is because the species generally live a long time and can afford to spend time on parenting.

  • ex: elephants (all mammals and some birds)

  • low biotic potential because they take a long time to raise young—creates slow population growth

  • more likely to be disrupted by environmental change and invasive species because of population size

  • Death of a parent means death of the offspring

• R selected: Value quantity, making many offspring in hopes that some of them survive. TYPE 3

  • they live shorter lives and often only reproduce once

  • produce many offspring at once in hopes they survive

  • ex: spiders—children are left to fend for themselves. also includes plants, fish, and insects

  • High biotic potential creates population growth

  • more likely to be invasive and are better suited to environmental change and outcompete slower-growing K species for food or water

• Biotic Potential: Maximum reproduction rate of a population

  • higher for r-selected than for k-selected

  • not all species are k or r selected, more of a spectrum: Think of cats and dogs—high numbers of offspring at a time, but not left to fend for themselves

Trends in survivorship:

• type 1: K-selected species—high survivorship due to parental care. High survivorship in MID-LIFE due to large size and defensive behavior—rapid decrease in late life (applies to most mammals)

• type 2: In between K and R selected traits—steadily decreasing survivorship throughout life; found in smaller organisms like birds and rodents or those that are unable to protect themselves well (susceptible to temperature)

• type 3: Mostly R-selected species—high mortality in early life due to lack of parental care. Few organisms make it to mid-life, and a steady decline in mid-life leads to fewer organisms living to adulthood. Lots of offspring compensate for low survivorship

Carrying capacity: The maximum occupancy limit of an ecosystem

• determined by the resources available to occupants

• Limiting Factors: Space (ie Nesting space, territory, etc), food, water

• carrying capacity is different for each species (based on habitat and food needs)