Chapter 6

1. Chapter 6 Ecosystem Balance

2. Ecosystem Balance • 6.1 Relationships in the Ecosystem • 6.2 Ecological Succession • 6.3 Stability in the Ecosystem • 6.4 Land Biomes

3. 6.1 Relationships in the Ecosystem • Objectives • Explain the relationship between the population sizes of predator and prey. • Define symbiosis and describe several symbiotic relationships.

4. Relationships in the Ecosystem • A complex web of relationships exist among all the species in an ecosystem. • Scientists study these relationships by: • Studying how two populations interact with one another. • Expanding the knowledge they have gained to other parts of the ecosystem.

5. Predator and Prey • One of the relationships ecologists study is that of predator and prey. • Define Predator. • Define Prey • Examples

6. Predator and Prey

7. Predator and Prey • The sizes of predator and prey populations are closely linked. • Figure 6.1 p. 89 • Prey experience populations cycles. • A predator’s populations cycle mimics that of its prey.

8. Parasitism • Some animals do not kill the prey they feed on. • Parasitism-an organism that feeds on the tissue or body fluids of another organism • Host-the organism the parasite feeds off of • Examples

9. Parasites-Tapeworms and Roundworms

10. Symbiosis • Symbiosis-a relationship in which two species live closely together • Three types: • Parasitism-one is helped and the other is harmed (typically) • Commensalism- one organism benefits and the other is neither helped or harmed • Examples • Mutualism-both organism benefit • Examples

11. Commensalism

12. Mutualism

13. Questions • What is the relationship between the population sizes of predator and prey. • Define Symbiosis • What are some examples of symbiotic relationships?

14. 6.2 Ecological Succession

15. Objectives • Contrast primary and secondary succession. • Describe the sequence of ecological succession in a lake and on an island.

16. Ecological Succession • Organisms affect their environment • Example: Plants  Soil • Changes are not always beneficial • Old niches are replaced by new niches. • Other forces can cause change in the environment. • Example: Forest Fire

17. Ecological Succession • As environment change the communities living in that environment change as well. • In many cases different communities follow one another in a definite pattern, this is called succession.

18. Volcano Eruption • A volcano erupts leaving the land covered in bare black rock…it is lifeless. • Does it stay this way?

19. Volcano Eruption (cont) • No • Almost immediately organisms begin to inhabit the area.

20. Primary Succession • Define Primary Succesion • Examples: Cooled lava fields and exposed rock from retreating glaciers.

21. Primary Succession • Primary succession is an orderly process. • Follows the same general pattern in most ecosystems.

22. Step 1 • Colonization by new organisms and formation of soil from exposed rock. • On land this is done by lichens. • Define lichens. • Lichens can live on bare rock.

23. Step 1 (cont) • Lichens secret acids that break down the rock and form organic material by photosynthesis. • Weathering also breaks down rocks. • Soil is formed by the actions of the lichens and weathering.

24. Pioneer Community • Lichen Community • First community to colonize the area.

25. Step 2 • Once soil is formed, grasses and other small plants begin to grow. • Root growth and accumulation of dead leaves  Soil formation • Plants grow dense  lichen disappear

26. Grass Community • Survives for many generations and makes the soil deeper and more fertile. • Soil is deep enough  Growth of nonwoody plants with deep roots (Heath Mat). • These plants are taller and shade out the grasses. • Since the grass/shrub community is not diverse a small disturbance may cause drastic change.

27. Pines and other tress • Pines or other trees with shallow roots are next. • Trees shade out the heath mat.

28. Broadleaf and Hardwood Trees • As the soil deepens even further broadleaf and hardwood trees take over. • Hardwood forest in the final stage of succession in many areas.

29. Climax Community • A community that does not undergo further succession. • Climax communities are usually highly diverse and can often survive even severe local disturbances.

30. Primary Succession

31. Primary Succession • Only occurs on freshly exposed rock or in places where a severe disturbance has occurred. • However most disturbances are not this drastic.

32. Secondary Succession • A fire may kill many plants but leave the soil in place. • Living things can quickly colonize these types of areas. • Define Secondary Succession. • Examples: Storms, Fires and human activity

33. Deforestation

34. Secondary Succession • Secondary succession resembles the later stages of primary succession. • 1st to colonize are: • Next to colonize: • Final to colonize:

35. Secondary Succession • Research has shown that many habitats never develop climax communities. • Why? • Example

36. Secondary Succession

37. Aquatic Succession • Newly formed mountain lake. • Low nutrient levels • Supports few organisms. • Reeds and other aquatic plants. • Organic matter builds up and lake fills with sediment. • Nutrient rich water • Increase in wildlife • Water plants cover the surface. • Lake fills with sediment Marsh • Land plants begin to colonize • Finally Fertile Meadow (possibly a forest)

39. Island Succession • Similar to succession on the continents. • Any organisms found on an island must have ancestors that were: • Carried by water • Carried by wind • Carried by other organisms • Many islands have large bird populations.

40. Island Succession • There are many unfilled niches on islands. • Organisms can evolve to fit many niches. • When a population of organisms adapted to their new niches new species are formed. • Example: Figure 6.9 p. 95

41. Review • How does primary and secondary succession differ from each other? • What is a climax community? • What is a pioneer community? • Describe the sequence of ecological succession in a lake and on an island.

42. 6.3 Stability in the Ecosystem

43. Objectives • Explain the concept of ecosystem stability. • Characterize the effects of disturbances on the ecosystem

44. Stability is a measure… • …of how easily an ecosystem is affected by a disturbance. • …how quickly it returns to its original condition after a disturbance. • Conditions include: biotic and abiotic factors, patterns of energy flow and nutrient cycling.

45. More stable ecosystem • Will return steady pattern of energy flow • Experience fewer food web changes. • Fewer evolutionary changes • Fewer changes in the abiotic environment.

46. Stability in the Ecosystem • Determined by the complexity of food web • Manages the system’s energy flow and nutrient cycles. • More connections=stability • Impact of disturbance is less.

47. Equilibrium • State of balance • Changes counteract other changes. • Weather cooling is counteracted by the evolutionary adaptation to cold weather. • Disturbed ecosystem returns to a state of equilibrium (balance).

48. Ecosystem Function • Scientist do not understand every detail of how even simple ecosystems function. • They do understand that a change in one part of triggers a change in another. • Scientists are trying to apply the chaos theory.

49. Chaos Theory • A type of mathematics • Suggests that ecosystem may be sensitive to even small changes • The beginning state of an ecosystem is crucial to its later development.

50. Species Extinction • Species are becoming extinct at an alarming rate. • Fastest since the extinction of dinosaurs. • Possible causes: • Human Growth • Habitat destruction • Introduction of foreign species • Pollution of fresh water