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POPULATIONS

Leyda. POPULATIONS. I. DESCRIBING A POPULATION. Geographic distribution : the area inhabited by a population. I. DESCRIBING A POPULATION. 2. Population density : the number of individuals per unit area . I. DESCRIBING A POPULATION.

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POPULATIONS

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  1. Leyda POPULATIONS

  2. I. DESCRIBING A POPULATION • Geographic distribution: the area inhabited by a population.

  3. I. DESCRIBING A POPULATION 2. Population density: the number of individuals per unit area.

  4. I. DESCRIBING A POPULATION • Population density: the number of individuals per unit area. a. high density: lots of individuals per unit area

  5. I. DESCRIBING A POPULATION • Population density: the number of individuals per unit area. a. high density: lots of individuals per unit area b. low density: few individuals per unit area

  6. I. DESCRIBING A POPULATION • Growth Rate: how quickly a population changes in size. Fast Growth Rate: Slow Growth Rate: 55 Minutes! 55 Years!

  7. II. FACTORS AFFECTING POPULATION GROWTH • ________ rate • ________ rate • birth rate = death rate  population size _________________ • birth rate > death rate  population size _________________ • birth rate < death rate  population size _________________ Birth Death stays the same increases decreases

  8. II. FACTORS AFFECTING POPULATION GROWTH 3. immigration: _________________________________ a. example: ___________________________________________ movement of individuals into an area bison immigrates to a meadow full of grass

  9. II. FACTORS AFFECTING POPULATION GROWTH 4. emigration: _________________________________ a. example: ___________________________________________ movement of individuals out of an area bison emigrates out of a meadow without grass

  10. III. Types of Growth 1. ______________ growth: _________________________________ Individuals reproduce at a constant rate Exponential

  11. III. Types of Growth • ____________ growth: ________________________________ a. Conditions necessary for exponential growth 1. Unlimited resources 2. Absence of disease and predators b. Example: Bacteria will double their population in 20 mins Individuals reproduce at a constant rate Exponential Staphylococcus aureus

  12. III. Types of Growth c. Shape of graph: J-shaped d. Graph example: Notice: as time goes on, population increases exponentially.

  13. III. Types of Growth • ________ growth: ______________________________________ _____________ a. When does population growth slow or stop? 1. Birthrate – Down 2. Immigration – Down 3. Death rate – Up 4. Emigration – Up b. Example: Any animal population in nature. Logistic Population grows rapidly until some factor limits growth

  14. III. Types of Growth c. Shape of graph: S-shaped d. Graph example: Notice: as time goes on, population increases then hits a limit and levels off. This limit is the carrying capacity for that population.

  15. III. Types of Growth e. Carrying capacity: Maximum number of individuals that an area can support.

  16. IV. Limits to Growth Limiting factor: something that causes population growth to decrease. VS

  17. IV. Limits to Growth A. Density-dependent limiting factors: When population is high these take effect. 1. Competition: Organisms compete for food, water, space, sunlight, and other essentials. Example: Birds and mice both eat seeds. Effect on Evolution: Both species are put under pressure to change in ways that decreasecompetition. Remember Competitive Exclusion Principle!

  18. IV. Limits to Growth 2. Predation: One organism eats another. Example: Lynx eats rabbit. Predator: LynxPrey:Rabbit Effect on Evolution: Prey species (rabbit) evolves defenses (speed, camouflage), predators evolve counter-defenses (eyesight).

  19. IV. Limits to Growth Parasitism/disease: Organisms live in and on a host organism. Examples: Ticks, fleas, leeches, tapeworms, bacteria

  20. IV. Limits to Growth B. Density-independent limiting factors: Not related to population size. 1. random events: Unusual weather, natural disasters: volcanoes, hurricanes, floods, ice age

  21. Density-independent limiting factors: Not related to population size. • 2. human disturbances – such as damming rivers and clear-cutting forests.

  22. Density dependent or Independent? • Lava Flow • Number of predators • Spread of disease • Especially cold winter • Toxic chemical spill into a stream • Another species competing for same resource • Diverting river for irrigation • Beetles that attack trees

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