Ecology Part 1 11-12


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Ecology Part 1 11-12

  1. 1. What is ecology?The study of interactions betweenorganisms and their environment.
  2. 2. Ecology? Biology? Biology is simply the “study of life.” Ecology involves the interactions of living and nonliving aspects of the environment. Both biotic and abiotic factors are interconnected – a change in one, changes all the others over time.
  3. 3. Factors Biotic Factors  Living factors  Humans, plants, insects Abiotic Factors  Nonliving factors  Physical & chemical characteristics  Temperature, pH, O concentration, 2 sunlight, H2O, soil
  4. 4. Abiotic? Biotic? Exploding human population  Biotic Species endangerment/extinction  Biotic Thinning of the ozone layer  Abiotic Greenhouse effect  Abiotic
  5. 5. Interactions at Levels Organism  A single species  Example: one blue gill  Note: Since no organism is isolated, ecologists must use MODELS to study the environment and to make predictions about the future
  6. 6. Interactions at Levels Population  Members of a single species  Example: population of blue gills in a lake
  7. 7. Interactions at Levels Community  A group of different populations that live in the same area  Only living factors in an area interacting with each other  Example: fish, turtles, algae
  8. 8. Interactions at Levels Ecosystem  The interactions among living things and the nonliving things in an area  Example: lake  NOTE: Biomes are large ecosystems
  9. 9. Interactions at Levels Biosphere  Broadest category  The part of Earth where living things exist  Example: atmosphere, lithosphere
  10. 10. Organisms Habitat  Where an organism lives Niche  What an organism does (its job or role) in its environment  Role in the food chain & nutrient cycling  Interactions with other species  Two types of niches  Fundamental niche  Realized niche
  11. 11. Fundamental Niche The potential range of conditions and resources that an organism can assume Total range of environmental conditions that are suitable for a species existence Example:  We can live anywhere in U.S. (tolerance)
  12. 12. Realized Niche The actual range of conditions and resources that an organism assumes Example:  We live and do our “jobs” in Northbrook.
  13. 13. Ecological Roles Generalists  Organisms with very broad niches  Can live in many habitats, many conditions  “Jack of all trades, master of none”  Example:  Opossum  Cockroaches  Mice  Humans
  14. 14. Ecological Roles Specialists  Organisms with very narrow and specific niches  Live in one or few habitats, narrow range of conditions  Out compete generalists in preferred habitats  Example:  Koala can only live and survive on Eucalyptus trees in Australia
  15. 15. Ecological Roles In a changing environment, it is better to be a generalist. In a stable environment, it is better to be a specialist.
  16. 16. What is a population?All the individuals of a single species living in an area
  17. 17. Rabbits in Australia
  18. 18. Population Size? Density? Population Size  Number of individuals Population Density  Number of individuals in an area  Persons/square mile
  19. 19. Limiting Factors Density dependent limiting factors  Factors that limit a population only when a population reaches a certain density  Examples:  Competition, predation, parasitism, disease, water availability
  20. 20. Limiting Factors Density independent limiting factors  Factors that affect all population in the same way regardless of density  Examples:  Weather, natural disasters, seasonal cycles, pollution
  21. 21. Growth Rate Change in population size over time Depends on births, deaths, immigration (in), and emigration(out).
  22. 22. Growth Rate Populations grow exponentially until they reach carrying capacity (the maximum number of organisms that an area can support) Example:  1, 2, 4, 8, 16, 32….
  23. 23. Population Growth Models Exponential (J-shaped) Growth Curve Logistic (S-shaped) Model Boom and Bust Model
  24. 24. Exponential (J-shaped) Growth Curve Ideal Model Under ideal conditions: plenty of resources, no competition, no parasites, no predators, etc. Because of limiting factors, populations rarely exhibit J-shaped growth curves
  25. 25. Logistic (S-shaped) Model Realistic model Rapid growth, then slowing of growth and leveling off Regulated by carrying capacity (# of individuals which can be supported by resources of environment without damage to environment) Generally density dependent  Growth is affected by the density of individuals
  26. 26. Boom and Bust Model Example:  26 reindeer were introduced onto an island off the coast of Alaska in 1910.  Within 30 years the herd increased to 2,000.  However, overgrazing reduced the food supply and the population crashed to 8 animals by 1950.
  27. 27. Boom and Bust Model Realistic Model Growth occur exponentially, but crash due to…  Disturbance, such as weather  Overexploitation of environment