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Aug 25th, 2019
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  1. Changes in Ecosystems
  2. Ecological Success
  3. • What is Ecological Succession?
  4. Natural, gradual changes in the types of species that live in an area
  5. • Can be primary or secondary
  6. • The gradual replacement of one plant community by another through natural processes over time
  8. Primary Succession
  9. • Begins in a place without any soil: Sides of volcanoes, landslides, flooding
  10. • First, lichens that do not need soil to survive grow on rocks
  11. • Next, mosses grow to hold newly made soil
  12. • Known as PIONEER SPECIES
  13. • Lichens break down rock to form soil. Low, growing moss plants trap moisture and prevent soil erosion
  14. • Soil starts to form as liches and the forces of weather and erosion help break down rocks into smaller pieces
  15. • When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil
  16. • Simple plants like mosses and ferns can grow in the new soil
  17. • The simple plants die, adding more organic material (nutrients to the soil)
  18. The soil layer thickens, and grasses, wildflowers, and other plants begin to take over
  19. • These plants die, and they add more nutrients to the soil
  20. • Shrubs and trees can survive now
  21. • Insects, small birds, and mammals have begun to move into the area
  22. • What was once a bare rock, now supports life
  24. Secondary Succession
  25. • Begins in a place that already has soil and was once a home of living organisms
  26. • Occurs faster and has different pioneer species than primary succession
  27. • Example: after forest fires
  29. Climax Community
  30. • A stable group of plants and animals that is the end result of the succession process
  31. • Does not always mean big trees
  32. -Grasses in prairies
  33. -Cacti in deserts
  38. Two types of limiting factors:
  39. Density-dependent and Density-independent
  40. Population density describes the number of individuals in a given area
  41. Density – Dependent
  42. • Density-dependent factors include disease, competition, predators, parasites, and food
  43. • Disease, for example, can spread more quickly in a population with members that live close together
  44. Density – Independent
  45. • Density-independent factors can affect all populations, regardless of their density
  46. • Most density-independent factors are abiotic factors, such as temperature, storms, floods, drought, and major habitat disruption
  47. Organism Interactions
  48. • Population sizes are controlled by various interactions among organisms that share a community
  49. • Predation and competition are two interactions that control populations
  50. Predation – Populations of predators and their prey experiences cycles or changes in their numbers over periods of time
  51. Competitions
  52. • Is Density – Dependent
  53. • When only a few individuals compete for resources, no problem arises
  54. • When a population increases to the point at which demand for resources exceeds the supply, the population sizes decreases
  56. Crowding
  57. • As populations increase in size in environments that cannot support increased numbers,
  58. • Individual animals can exhibit a variety of stress symptoms
  59. • These include aggression, decrease fertility, and decreased resistance to disease
  60. • They become limiting factors for growth and keep populations below carrying capacity
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