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

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)
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

51. Thought
It is difficult for scientists to predict the long-term effects of humans on the biosphere.
And for them to predict the ability of the biosphere to support human population.

52. Review What makes an ecosystem stable?
What happens to a stable ecosystem when a disturbance occurs?
What happens to a ecosystem that is unstable when a disturbance occurs?

53. 6.4 Land Biomes

54. Objectives
Explain the concept of the biome, and name the eight major land biomes.
Name an area in which each type is located.

55. Biomes Earth is very large and diverse
Environments range from the ice of Antarctica to the heat and rain of the Amazon.
Difference in temperature and rainfall create a vast array of conditions.
Life has adapted to almost all of these conditions.

56. Biomes
Definition-major type of ecosystem with distinctive temperature, rainfall and organisms.
Either terrestrial or aquatic.

57. Biomes
Biome is the largest general category used to classify ecosystems
Conditions may vary from place to place
Smaller ecosystems within a biome may have different habitats with different conditions and organisms.
Every habitat on Earth is different.
Term Biome is useful when discussion related habitats.

58. Aquatic Biomes
Determined by:
Water depth
Nutrients
Nearness to land

59. Terrestrial Biomes Determined by: Average temperature
Amount of precipitation
8 major types of land biomes
Desert
Tundra
Coniferous forest
Deciduous forest
Rain forest
Steppe
Prairie
Savanna

60. Desert Low humidity High summer temperatures Low annual rainfall
Supports only a small amount of biomass
Deserts cover 25% of Earth’s land surface
Deserts contain only 1% of Earth’s biomass
Plant life is scarce in a desert due to lack of water

61. Desert in Australia

62. Tundra
Cold
Windy
Dry
South of polar ice caps in Alaska, Canada, Greenland, Iceland, Norway and Asia
Very little plant life due to lack of water

63. Tundra

64. Forest Biomes Contains 75% of Earth’s Biomass Three types:
Coniferous forest- containing conifers.
Deciduous forest – containing deciduous trees.
Rain forest –dense canopy of evergreen, broadleaf trees that receives at least 200 cm of rain each year.

65. Deciduous Forest

66. Coniferous Forest - Yosimite

67. Amazon Rain Forest

68. Rain forest Covers only 6% of Earth’s land surface.
Contains more than 50% of all Earth’s biomass.
Most diverse biome.
Destruction of the rain forest is a HUGE environmental problem

69. Grasslands Cover 22% of Earth’s land surface
Contain 8% of Earth’s biomass.
Grasslands receive less precipitation than do forests and may have long dry seasons.
May experience frequent fires
Home to large herds of migrating herbivores
Three types:
Steppe
Prairie
Savanna

70. Steppe Grassland Biome Receives less than 50cm of rain per year
Characterized by short bunchgrasses.

71. Steppe

72. Prairie Grassland Biome Characterized by: Rolling hills Plains
Sod-forming grasses

73. Prairie

74. Savanna Grassland Biome Tropical
Ranging from dry scrubland to wet, open woodland

75. Savanna - Africa

76. Review What is a biome? What are the 8 major types of land biomes?
What type of land biome covers the largest land area?
What type of land biome contains the most biomass?