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Populations

Learn how populations change over time due to interactions with the environment. Explore population characteristics, growth rates, carrying capacity, and limiting factors affecting growth. Understand exponential and logistic growth, density-dependent and density-independent factors.

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Populations

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  1. Populations Notes #44 I can: Understand factors that cause populations to change over time

  2. The interaction of organisms with the living and nonliving parts of their environment cause their populations to change over time.

  3. Characteristics of Populations Some important characteristics of a population include its geographic distribution, density and its growth rate. The geographic distribution of a population has to do with how individuals are spread out in space.

  4. Population Density Population density is the number of individuals per unit area. Many individuals in one area = high population density. Few individuals in one area = low population density.

  5. Growth Rate A population can grow when its birth rate is greater than its death rate. During which time period was this population growing? How do you know? What happens to a population if the birthrate equals the death rate? What happens when the death rate of a population is greater than its birth rate?

  6. Exponential Growth Exponential growth occurs under ideal conditions with unlimited resources. Individuals reproduce at a constant rate.

  7. Bacteria growing under ideal conditions in a laboratory exhibit exponential growth.

  8. Logistic Growth Logistic growth occurs when a population’s growth rate reaches zero as resources become less available following a period of exponential growth. The population has reached its carrying capacity, or the largest number of individuals that a given environment can support.

  9. Carrying Capacity As a population overshoots its carrying capacity, it will fluctuate. Crashes are common as the environment can no longer support the population.

  10. Guided Practice Draw and label the appropriate shape to represent either exponential or logistic growth for the given scenarios.

  11. Population increases indefinitely.

  12. Population increase rapidly at first, and then flattens out.

  13. Occurs as resources become less available.

  14. Occurs under ideal conditions.

  15. Occurs when birth rate is greater than death rate.

  16. Occurs when birth rate and death rate are equal.

  17. Occurs when an ecosystem’s carrying capacity is reached.

  18. Elephants have no natural predators except for humans. Describe the population growth of elephants after they are protected from hunting.

  19. Workers at Chipotle often leave out raw chicken for several hours at room temperature. Describe the growth of the Salmonella on the chicken.

  20. What causes population growth to decrease?

  21. Limiting Factors Limiting factors are things that limit population growth.

  22. Density-Dependent Limiting Factors Density-dependent limiting factors depend on population size and have a greater affect on populations with greater densities. predation/ competition parasitism disease

  23. Predation What is the relationship between hare and lynx population sizes? Predation regulates the population size of prey, and prey population regulates the population size of the predator.

  24. Density-Independent Factors Density-independent limiting factors affect all populations in similar ways, regardless of size. human impacts unusual weather natural disasters fire

  25. Who is most affected? Many individuals in one area = high population density. Few individuals in one area = low population density.

  26. Write on your board What is the name for the part of a population graph that shows when a population has become stable, neither growing nor becoming smaller?

  27. Write on your board When a population exceeds its carrying capacity, it will ______________.

  28. Write on your board When a population has not yet reached its carrying capacity, it will ______________.

  29. Write on your board Name a density-dependent limiting factor that affects population size.

  30. Write on your board If the amount of food in an area increased, how is the carrying capacity affected?

  31. Write on your board Which type of population will disease impact the most?

  32. Write on your board How can the birth rate of a population be increasing, but the total population be decreasing?

  33. Write on your board Which explains why the size of a population of rabbits might be decreasing? • The disease rate of the rabbit population is low. • The rate at which the rabbits reproduce is increasing. • The birth and death rates of the rabbits have stabilized. • Rabbits are dying at a faster rate than they are reproducing.

  34. Write on your board Which describes the impact predators have on the population growth of the prey? • Predators maintain the prey population. • Predators increase the prey population growth. • Predators decrease the prey population growth. • Predators have no impact on the prey population growth.

  35. Write on your board Ten fish were living well in a 10-gallon fish tank. When five fish were added to the tank later, some fish began to die. Which best explains this occurrence? • The fish ran out of CO2. • The fish had no space in which to swim. • The fish exceeded the carrying capacity of the tank. • The new fish began to use the older fish for food.

  36. Team Attack • Each group starts off with 10 X’s on the board. • A question will be presented on the SmartBoard, and each team has 1 minute to write their answer on their whiteboard and hold it up when time is called. • When time is up, I’ll pick a stick, and whoever’s team is picked gets a chance to attack – if they got the answer right. • If you get the question right, 1 person from each team may come up and remove the number of X’s indicated on the board. The team with the most X’s at the end wins!

  37. 1. Which elements are recycled in the water cycle? 2

  38. 2. Which molecule is the atmospheric form of carbon in the carbon cycle? • CO2 • C6H12O6 • O2 • CO 2

  39. 3. List one example of a biotic factor that influences an ecosystem 2

  40. 4. List one example of an abiotic factor that influences an ecosystem 2

  41. 5. If the owls increase, how will this affect the amount of grain? 2

  42. 6. How does an autotroph get its energy? 2

  43. 7. What is another name for an autotroph? 2

  44. 8. How does a heterotroph get its energy? 2

  45. 9. Which organism has the most energy in the energy pyramid? 4

  46. 10. How much energy is NOT passed on to the next trophic level in an energy pyramid? 4

  47. 11. What are TWO ways that carbon dioxide is added to the atmosphere? 4

  48. 12. Why is photosynthesis important for heterotrophs? 4

  49. 13. What is the role of respiration in the carbon cycle? 4

  50. 14. Which level of ecological organization includes both biotic and abiotic factors? • Population • Community • Ecosystem • Individual 4

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