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CHAPTER 35

CHAPTER 35. POPULATION AND COMMUNITY ECOLOGY. Concept 35.2. THERE ARE LIMITS TO POPULATION GROWTH. CARRYING CAPACITY. Carrying capacity : the number of organisms that the environment can maintain with no net increase or decrease

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CHAPTER 35

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  1. CHAPTER 35 POPULATION AND COMMUNITY ECOLOGY

  2. Concept 35.2 THERE ARE LIMITS TO POPULATION GROWTH

  3. CARRYING CAPACITY • Carrying capacity: the number of organisms that the environment can maintain with no net increase or decrease • Limiting factor: any condition that restricts the growth of a population - may be biotic or abiotic - examples : climate, disease, availability of food, space

  4. FACTORS AFFECTING POPULATION GROWTH • Density dependent factors: limit population more as population density increases • EXAMPLES: - availability of food - diseases that spread more rapidly in dense populations

  5. FACTORS AFFECTING POPULATION GROWTH • Density independent factors: factors unrelated to population density • EXAMPLES: - extreme weather events (blizzards, hurricanes, droughts, floods) - insects

  6. POPULATION GROWTH CYCLES • “boom & bust” cycles: populations increase rapidly for a time, then rapidly decline • POSSIBLE CAUSES: - stress from crowding - size of other populations influences food availability

  7. Concept 35.4 SPECIES INTERACT IN BIOLOGICAL COMMUNITIES

  8. COMPETITION BETWEEN SPECIES • Interspecific competition: occurs when two or more species rely on the same limited resource - generally related to limited supplies of food or water

  9. SYMBIOTIC RELATIONSHIPS • Symbiosis: close interaction between species in which one lives in or on the other 3 main types • Parasitism: one organism obtains its food at the expense of the other (mosquitoes) • Mutualism: both organisms benefit (intestinal bacteria) • Commensalism: one organism benefits while the other organism is neither harmed nor benefits significantly (spider crab & seaweed)

  10. Concept 35.5 DISTURBANCES ARE COMMON IN COMMUNITIES

  11. ECOLOGICAL SUCCESSION • Primary succession: community arises in a lifeless area that has no soil—volcanic islands • Microorganisms arise first, then lichens & mosses via windblown spores • Soil gradually forms resulting in grasses, shrubs, & trees from seeds dropped by birds

  12. ECOLOGICAL SUCCESSION • Secondary succession: Change that follows a disturbance that damages an existing community but leaves the soil intact • Examples: • Forested areas cleared for farming • Natural disasters  volcanic eruptions, hurricanes

  13. HUMAN ACTIVITIES AND SPECIES DIVERSITY • Of all species, humans have greatest impact on communities worldwide • 60% of all land is used by humans mainly as rangeland or cropland • Human activities usually have negative effect on the environment

  14. INTRODUCED SPECIES • Introduced species: (exotic species) organisms that humans move from the species native location to new geographic areas • Move may be accidental or intentional • Some introduced species may not survive, but others may gain foothold and disrupt their new community

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