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Ecology. Part 4. Populations Part 5. Communities Part 6. Biodiversity and Conservation. Population Ecology: Population Characteristics. Population Characteristics. Population Density: The number of organisms per unit area Spatial Distribution:

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Ecology l.jpg

Ecology

Part 4. Populations

Part 5. Communities

Part 6. Biodiversity and Conservation


Population characteristics l.jpg

Population Ecology: Population Characteristics

Population Characteristics

  • Population Density:

    • The number of organisms per unit area

  • Spatial Distribution:

    • Dispersion: The pattern of spacing a population within an area

    • 3 main types of dispersion

      • Clumped

      • Uniform

      • Random

    • The primary cause of dispersion is resource availability


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Population Ecology: Population Characteristics

Population Limiting Factors

  • Population growth rate

    • How fast a given population grows

    • Factors that influence this are:

      • Natality (____ rate)

      • Mortality (_____ rate)

      • Emigration (the number of individuals moving _________ a population)

      • Immigration (the number of individuals _________ a population)

birth

death

away from

moving to


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Population Ecology: Density-independent factors

Population Limiting Factors

  • Density-independent factors

    • Factors that limit population size, regardless of population density.

    • These are usually abiotic factors

    • They include natural phenomena, such as weather events

      • Drought, flooding, extreme heat or cold, tornadoes, hurricanes, fires, etc.


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Population Ecology: Density-dependent factors

Population Limiting Factors

  • Density-dependent factors

    • Any factor in the environment that depends on the number of members in a population per unit area

    • Usually biotic factors

    • These include

      • Predation

      • Disease

      • Parasites

      • Competition


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Understanding Exponentials

Population Ecology: Population Growth Rate

  • Put your pens down for a minute & think about this:

    • An employer offers you two equal jobs for one hour each day for fourteen days.

    • The first pays $10 an hour.

    • The second pays only 1 cent a day, but the rate doubles each day.

    • Which job will you accept?


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Population Ecology: Population Growth Rate

Understanding Exponentials

Now, how much would your employer owe you if you stayed at this job for another 2 weeks?

Job 2 lags for a long time before exponential growth kicks in!

What would happen if this type of growth took place within a population?


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Population Ecology: Population Growth Rate

Population Limiting Factors

  • Population growth models

    • Exponential growth model

      • Also called geometric growth or J-shaped growth.

      • First growth phase is slow and called the lag phase

      • Second growth phase is rapid and called the exponential growth phase

      • Bacteria can grow at this rate, so why aren’t we up to our ears in bacterial cells?


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Population Limiting Factors

Population Ecology: Population Growth Rate

  • Population growth models

    • Limits to exponential growth

      • Population Density (the number of individuals per unit of land area or water volume) increases as well

      • Competition follows as nutrients and resources are used up

      • The limit to population size that a particular environment can support is called carrying capacity (k)

    • When you’re done writing, put your pens down…


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Population Ecology: Population Growth Rate

What population do you think this is?


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So, what do you think is going to happen to the human population?

  • We will probably reach our carrying capacity.

  • Our growth rate will start to look like most organisms, which is the Logistic Growth Model

Carrying Capacity (k)

What letter does this curve kind of look like?


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Population Limiting Factors population?

Population Ecology: Population Growth Models

  • Population growth models

    • Logistic Growth Model

      • Often called the S-shaped growth curve

      • Occurs when a population’s growth slows or stops following exponential growth.

      • Growth stops at the population’s carrying capacity

      • Populations stop increasing when:

        • Birth rate is less than death rate(Birth rate < Death rate)

        • Emigration exceeds Immigration (Emigration > Immigration)


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Population Limiting Factors population?

Population Ecology: Population Growth Models

  • Population growth models

    • Logistic Growth Model

      The S-curve is not as pretty as the image looks

      • Carrying capacity can be raised or lowered. How?

        Example 1: Artificial fertilizers have raised k

        Example 2: Decreased habitat can lower k

      • Populations don’t reach k as smoothly as in the logistic graph.

        • Boom-and-Bust Cycles

        • Predator-Prey Cycles


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Community Ecology: Communities population?

Communities

  • Review:

    • A community is a group of interacting populations that occupy the same area at the same time.


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Community Ecology: Communities population?

Communities

  • Limiting Factors

    • Any abiotic or biotic factor that restricts the numbers, reproduction, or distribution of organisms.


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Community Ecology: Communities population?

Communities

  • Range of Tolerance

    • The limits within which an organism can exist.


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Community Ecology: Ecological Succession population?

Ecological Succession

  • Ecological Succession

    • The change in an ecosystem that happens when one community replaces another as a result of changing biotic and abiotic factors


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Community Ecology: Ecological Succession population?

Ecological Succession

  • Ecological Succession

    • Consists of 2 types:

      • Primary Succession

      • Secondary Succession


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Community Ecology: Ecological Succession: Primary Succession

Ecological Succession

  • Ecological Succession: Primary

    • The establishment of a community in an area of exposed rock that does not have topsoil is called Primary Succession.

      • It occurs very slowly at first


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Community Ecology: Ecological Succession: Primary Succession

Ecological Succession

  • Ecological Succession: Primary

    • The first organisms to arrive are usually lichens or mosses, which are called pioneer species.

      • They secrete acids that can break down rock

      • Their dead, decaying organic materials, along with bits of sediment from the rock make up soil.


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Community Ecology: Ecological Succession: Primary Succession

Ecological Succession

  • Ecological Succession: Primary

    • Small weedy plants and other organisms become established.

    • As these organisms die, additional soil is created


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Community Ecology: Ecological Succession: Primary Succession

Ecological Succession

  • Ecological Succession: Primary

    • Seeds brought in by animals, water and wind begin to grow in the soil.

    • Eventually enough soil is present for shrubs and trees to grow.


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Community Ecology: Ecological Succession: Primary Succession

Ecological Succession

  • Ecological Succession: Primary

    • The stable, mature community that eventually develops from bare rock is called a climax community.


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Community Ecology: Ecological Succession: Secondary Succession

Ecological Succession

  • Ecological Succession: Secondary

    • Disturbances (fire, flood, windstorms) can disrupt a community.

    • After a disturbance, new species of plants and animals might occupy the habitat.


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Community Ecology: Ecological Succession: Secondary Succession

Ecological Succession

  • Ecological Succession: Secondary

    • Pioneer species in secondary succession are usually plants that begin to grow in the disturbed area.

    • This is much fasterthan primarysuccession


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Community Ecology: Ecological Succession Succession

Ecological Succession

  • Ecological Succession: End point?

    • Cannot be predicted

    • Different rates of growth &human involvementmake it impossible toknow if a true climaxcommunity has beenreached.


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Biodiversity and Conservation: Introduction Succession

On the left side of your IntNB, address the following:

  • What would happen if all of the jackrabbits in a food web died suddenly?

  • Is the disappearance of one species from Earth important, or will another species fill its niche?


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Biodiversity and Conservation: What is biodiversity? Succession

Biodiversity

  • What is Biodiversity?

    The variety of life in an area that is determined by the number of different species in that area.

  • There are 2 main types:

Genetic Diversity

Species Diversity


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Biodiversity and Conservation: Why is biodiversity important?

Biodiversity

Penicillin: Derived from bread mold

Teosinte: A distant relative of corn

Domestic corn plant

Madagascar Periwinkle: Used to treat childhood forms of leukemia


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Biodiversity and Conservation: Extinctions important?

Extinction Rates

  • The gradual process of becoming extinct is known as background extinction.

  • Mass extinctions: When a large percentage of all living species become extinct in a relatively short period of time.

  • 250 MYA: Over90% of species died


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Biodiversity and Conservation: Extinctions important?

Estimated number of Extinctions since 1600


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Biodiversity and Conservation: Extinctions important?

Five Most Recent Mass Extinctions

Cretaceous Period (65 MYA)

Triassic Period (200 MYA)

Permian Period (250 MYA)

Devonian Period (360 MYA)

Ordovician Period (444 MYA)


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Activity: Understanding Geological Time important?

  • Working in your groups, you will get the following supplies:

    • A meter stick

    • A roll of 5 meters of paper

    • Colored pencils

  • Using the worksheet, plot out the dates.

    • 1 million years is a millimeter

    • 1 billion years is a meter