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Population Ecology and Ecosystems. Concepts and Applications: Chapters 40 & 43 Basic Concepts: Chapters 27 & 30. http://darwin.bio.uci.edu/~sustain/bio65/lec16/b65lec16.htm. Population Ecology. Ecology.

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Population Ecology and Ecosystems

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Population ecology and ecosystems l.jpg

Population Ecologyand Ecosystems

Concepts and Applications: Chapters 40 & 43

Basic Concepts: Chapters 27 & 30

http://darwin.bio.uci.edu/~sustain/bio65/lec16/b65lec16.htm


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PopulationEcology

Ecology

Ecology: The study of how organisms interact with one another and with their environment

  • Certain ecological principles govern the growth and sustainability of all populations

  • Human populations are no exception


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PopulationEcology

Human Population Problems

  • Over 6 billion people alive

  • About 2 billion live in poverty

  • Most resources are consumed by the relatively few people in developed countries


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PopulationEcology

Population

  • A group of individuals of the same species occupying a given area

  • Can be described by demographics

    • Vital statistics such as size, density, distribution, and age structure


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PopulationEcology

Population Age Structure

  • Divide population into age categories

  • Population’s reproductive base includes members of the reproductive and pre-reproductive age categories


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PopulationEcology

Density & Distribution

  • Number of individuals in some specified area of habitat

  • Crude density information is more useful if combined with distribution data

clumped

nearly uniform

Fig 40.2

random


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PopulationEcology

Mark and Recapture

# marked Captured = Number released

Total Captured Total Pop

Determining Population Size

  • Direct counts are most accurate but seldom feasible

  • Can sample an area, then extrapolate

  • Capture-recapture method is used for mobile species


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PopulationEcology

Assumptions in Capture-Recapture

  • Marking has no effect on mortality

  • Marking has no effect on likelihood to being captured

  • There is no immigration or emigration between sampling times


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PopulationEcology

Changes in Population Size

  • Immigration adds individuals

  • Emigration subtracts individuals

  • Births add individuals

  • Deaths subtract individuals


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PopulationEcology

Zero Population Growth- ZPG

  • Interval in which number of births is balanced by number of deaths

  • Assume no change as a result of migration

  • Population size remains stable


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PopulationEcology

Per Capita Rates

  • Rates per individual

  • Total number of events in a time interval divided by the number of individuals

  • Per capita birth rate per month =

    Number of births per month

    Population size


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PopulationEcology

Exponential Growth

Fig 40.4

  • Population size expands by ever increasing increments during successive intervals

  • The larger the population gets, the more individuals there are to reproduce


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PopulationEcology

r

  • Net reproduction per individual per unit time

  • Variable combines per capita birth and death rates (assuming both constant)

  • Can be used to calculate rate of growth of a population


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PopulationEcology

Exponential Growth Equation

G = rN

  • G is population growth per unit time

  • r is net reproduction per individual per unit time

  • N is population size


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PopulationEcology

Biotic Potential

  • Maximum rate of increase per individual under ideal conditions

  • Varies between species

  • In nature, biotic potential is rarely reached


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PopulationEcology

Space

Food

Shelter

Temperature

Mates

Pollution

Disease

Limiting Factors

  • Any essential resource that is in short supply

  • All limiting factors acting on a population dictate sustainable population size


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PopulationEcology

Carrying Capacity (K)

  • Maximum number of individuals that can be sustained in a particular habitat

  • Logistic growth occurs when population size is limited by carrying capacity


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PopulationEcology

Logistic Growth Equation

G = rmaxN (K-N/K)

  • G = population growth per unit time

  • rmax = maximum population growth rate per unit time

  • N = number of individuals

  • K = carrying capacity


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PopulationEcology

Logistic Growth

  • As size of the population increases, rate of reproduction decreases

  • When the population reaches carrying capacity, population growth ceases

carrying capacity

Time


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PopulationEcology

Overshooting Capacity

  • Population may temporarily increase above carrying capacity

  • Overshoot is usually followed by a crash; dramatic increase in deaths

Fig 40.7


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PopulationEcology

Resetting the Carrying Capacity

  • Major changes in environment can change the carrying capacity of a local system

Fig 40.6


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PopulationEcology

Density-Dependent Controls

  • Logistic growth equation deals with density-dependent controls

  • Limiting factors become more intense as population size increases

  • Disease, competition, parasites, toxic effects of waste products


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PopulationEcology

Density-Independent Controls

  • Factors unaffected by population density

  • Natural disasters or climate changes affect large and small populations alike


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PopulationEcology

Life History Patterns

  • Patterns of timing of reproduction and survivorship

  • Vary among species

  • Summarized in survivorship curves and life tables


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PopulationEcology

Life Table

  • Tracks age-specific patterns

  • Population is divided into age categories

  • Birth rates and mortality risks are calculated for each age category


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PopulationEcology

Survivorship Curves

Fig 40.8


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PopulationEcology

Human Population Growth

  • Population now exceeds 6 billion

  • Rates of increase vary among countries

  • Average annual increase is 1.26 percent

  • Population continues to increase exponentially


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PopulationEcology

Human Population Growth

1999

1975

domestication of plants, animals 9000 B.C. (about 11,000 years ago)

agriculturally based urban societies

beginning of industrial, scientific revolutions

Fig. 40.9, p. 695


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PopulationEcology

How Humans have Side-Stepped density dependent controls

  • Expanded into new habitats

  • Agriculture increased carrying capacity; use of fossil fuels aided increase

  • Hygiene and medicine lessened effects of density-dependent controls


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PopulationEcology

Population Momentum

  • Lowering fertility rates cannot immediately slow population growth rate. Why?

  • If every couple had just two children, population would still keep growing for another 60 years

Future Growth

  • Exponential growth cannot continue forever

  • Breakthroughs in technology may further increase carrying capacity

  • Eventually, density-dependent factors will slow growth


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PopulationEcology

Resource Consumption

  • United States has 4.7 percent of the world’s population

  • Americans have a disproportionately large effect on the world’s resources

  • Per capita, Americans consume more resources and create more pollution than citizens of less developed nations


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PopulationEcology

Effects of Economic Development

  • Total fertility rates (TFRs) are highest in developing countries, lowest in developed countries

  • When individuals are economically secure, they are under less pressure to have large families


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PopulationEcology

Slowing Growth in China

  • World’s most extensive family planning program

  • Government rewards small family size, penalizes larger families, provides free birth control, abortion, sterilization

  • Since 1972, TFR down to 1.8 from 5.7


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Community Ecology

Community Ecology

  • Community: Populations of all species in a habitat.

  • Niche: Sum total of all a species activities and relationships as species do what they do.

    • Fundamental, Realized


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Community Ecology

Types of Interactions

Who benefits?

Spp 1Spp 200Y0YYNNYNYN

  • Neutral

  • Commensalism

  • Mutualism

  • Competition

  • Predation

  • Parasitism


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Community Ecology

Competition

  • Competitive Exclusion

    • Paramecium

  • Resource Partitioning

    • Fruit eating birds, Barnacles


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Community Ecology

Predator-Prey Interactions

  • The Classic Lynx / Hare system


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Ecosystems

Ecosystems

  • Energy is transferred from the SUN to all organisms

  • Primary Producers

  • Consumers

  • Decomposers

  • Energy is LOST with each transition


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Ecosystems

Food Webs

MARSH HAWK

CROW

HIGHER TROPHIC LEVELS Complex array of carnivores, omnivores and other consumers. Many feed at more than one trophic level continually, seasonally, or when an opportunity presents itself

  • A composite picture of an ecosystem’s membership and their interaction

UPLAND SANDPIPER

GARTER SNAKE

FROG

WEASEL

BADGER

COYOTE

SPIDER

SECOND TROPHIC LEVEL Primary consumers (e.g., herbivores)

CLAY-COLORED SPARROW

POCKET GOPHER

EARTHWORMS, INSECTS (E.G., GRASSHOPPPERS, CUTWORMS)

PRAIRIE VOLE

GROUND SQUIRREL

FIRST TROPHIC LEVEL

Primary producers

Fig. 43.6, p. 740

Do not post photos on Internet


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Ecosystems

Food Webs can be Disrupted

  • Natural Disasters

  • External inputs

    • Pesticides, Pollution


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Ecosystems

Main Reservoirs

Volume (103 cubic kiometers)

Oceans

Polar ice, glaciers

Groundwater

Lakes, rivers

Soil moisture

Atmosphere (water vapor)

1,370,00029,000

4,000

230

67

14

The Hydrologic Cycle

ATMOSPERE

precipitation onto land 111,000

wind driven water vapor

40,000

evaporation from land plants (evapotranspiration) 71,000

evaporation from ocean

425,000

precipitation into ocean 385,000

surface and groundwater flow 40,000

LAND

OCEAN

Fig. 43.14, p. 746


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Ecosystems

Other Cycles

  • Carbon

  • Nitrogen

  • Phosphorus


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Quiz


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