Ecology
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Ecology. Population Dynamics. Why do we want to measure population sizes?. To better manage populations To better use resources increase population size endangered species (So they don’t go extinct) decrease population size pests maintain population size fisheries management

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Ecology

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Ecology

Ecology

Population Dynamics


Why do we want to measure population sizes

Why do we want to measure population sizes?

  • To better manage populations

    • To better use resources

      • increase population size

        • endangered species (So they don’t go extinct)

      • decrease population size

        • pests

      • maintain population size

        • fisheries management

          • maintain & maximize sustained yield


How do we measure plant and animal populations

How do we measure plant and animal populations?

  • Tagging (mark-recapture)

    • Netting

    • Electroshocking

    • Radio collars

    • Traps

  • Animal counts (ex: deer yards)

  • Counting plants

    • estimate over large areas


Fyke netting in spring

Fyke netting in spring


Tagging

Tagging


Electroshocking

Electroshocking


Electroshocking1

Electroshocking


Electroshocking2

Electroshocking

  • Stream electroshocking


Radio tracking

Radio tracking


Netting animals

Netting animals


Traps

Traps


What changes a population s size

What changes a Population’s Size?

  • Changes to population size

    • adding & removing individuals from a population

      • birth

      • death

      • immigration

      • emigration


Natural populations of organisms

Natural populations of organisms

  • Natural populations do NOT show linear growth!


Natural populations demonstrate exponential growth

Natural populations demonstrate exponential growth


Exponential growth rate

Exponential growth rate

  • Characteristic of populations without limiting factors

    • introduced to a new environment or rebounding from a catastrophe

Whooping crane

coming back from near extinction

African elephant

protected from hunting


Limits to population growth

Limits to population growth

  • Limiting factors –

    • any environmental factor that limits an organism’s ability to survive in its environment

    • Examples????

      • Predators


Regulation of population size

Regulation of population size

marking territory= competition

  • Limiting factors

    • density dependent

      • Biotic factors

        • competition: food, mates, nesting sites

        • predators, parasites, pathogens

    • density independent

      • abiotic factors

        • sunlight (energy)

        • temperature

        • rainfall

swarming locusts

competition for nesting sites


Carrying capacity

Carrying capacity

  • The number of organisms of one species that an environment can support over an extended period of time.


Carrying capacity1

10

8

Number of breeding male

fur seals (thousands)

6

4

2

0

1915

1925

1935

1945

Time (years)

500

400

Number of cladocerans

(per 200 ml)

300

200

100

0

0

10

20

30

40

50

60

Time (days)

Carrying capacity

  • Maximum population size that environment can support with no degradation of habitat

    • varies with changes in resources

What’s going on with the plankton?


Changes in carrying capacity

Changes in Carrying Capacity

  • Population cycles

    • predator – prey interactions

At what population level is thecarrying capacity?

K

K


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