NETA PowerPoint® Slides - WordPress.com · Title: Miller LITE 4ce_PPT_Ch09_edited Author: Maria...
Transcript of NETA PowerPoint® Slides - WordPress.com · Title: Miller LITE 4ce_PPT_Ch09_edited Author: Maria...
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Copyright © 2017 by Nelson Education Ltd.
NETA PowerPoint® Slidesto accompany
prepared byIan Dawe
Copyright © 2017 by Nelson Education Ltd.
Chapter 9
Population Ecology
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Key Concepts
Species response to environmental stress– Population size, density, makeup,
and distribution
Species reproductive patternsSpecies genetics influence population size and survivalHuman impacts on ecosystems
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Population Dynamics
Changes in population characteristics in response to environmental stress
• Size (number of individuals)• Density (individuals per area)• Age distribution
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Population Dispersion
(a) Clumped (e.g., reindeer)
(b) Uniform(e.g., birds nesting in a colony)
(c) Random(e.g., dandelions)
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Factors Governing Population Size
Age distribution– Reproductive stage
Biotic potentialEnvironmental resistance– Resource limits– Competition– Predation
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Ecological Trade-Offs
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Exponential vs. Logistic Population Growth
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Logistic Growth: Tasmanian Sheep
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Exponential Growth, Overshoot, Population Crash
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Population Density Affects Growth — Sometimes
Density-independent controls– For example, weather events, fire, habitat
destruction
Density-dependent controls– For example, competition, predation,
infection
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Natural Population Curves
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Predator-Prey Relationship Controls Population Size
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Source: Data from D. A. MacLulich
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How Do Species Reproduce?
Asexual reproductionSexual reproduction:Advantages– Genetic diversity– Males hunt, gather,
protect
Disadvantages– Males cannot give birth– Genetic errors– Courtship and mating
require time and risk
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What Reproductive Patterns Do Species Have?
r-selected species– High rate of population
increase– Opportunist species
K-selected species– Low rate of population
increase– Competitor species
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What Reproductive Patterns Do Species Have?
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Survivorship Curves
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Effects of Genetic Variations on Population Size
Can have greatest affect on small, isolated populationsLoss of genetic diversity due to:– Founder effect– Demographic bottleneck– Genetic drift– InbreedingMetapopulation interactions aid in survival of small populations
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Human Impacts on Natural Systems
Habitat degradation and fragmentationEcosystem simplificationUse and waste of primary resourcesGenetic resistancePredator eliminationIntroduction of non-native speciesOverharvesting renewable resourcesInterference with ecological systemsCreating fossil fuel dependent systems
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Human Footprint on the Land
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Source: Data from Wildlife Conservation Society and the Center for International Earth Science Information Network at Columbia University (CIESIN). Reprinted by permission.
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How Can We Live More Sustainably?
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How Can We Live More Sustainably?
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Growth of Whooping Crane Population
After falling to a population size of 22 in 1941, population has been growingApproaching wetland carrying capacityNumbers good, but flocks are still relatively small and isolated
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Source: Data from the International Crane Foundation and the U.S. Fish &Wildlife Service
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Conclusion
Population size and growth are determined by a number of factors.Environment imposes limits on population size.Populations can interact.At-risk populations can bounce back with good management.
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