1. Chapter 6: Ecosystems and Ecosystem Management

2. The Ecosystem: Sustaining Life on Earth
Sustaining life on Earth requires more than individuals
Life is sustained by interactions of many organisms functioning together in ecosystems
Physical and chemical environments

3. Basic Characteristics of Ecosystems
Ecosystems have several fundamental characteristics
Structure
Made up of two major parts; living (ecological community)and non living (physical chemical enviro)

4. Basic Characteristics of Ecosystems
Processes
Cycling of chemical elements and flow of energy
Change
Undergo development through succession

5. Basic Characteristics of Ecosystems
For complete recycling of chemical elements to take place, several species must interact.
Photosynthetic organisms produce sugar from carbon dioxide and water
From sugar and inorganic compound they make other organic compounds (protein, woody tissue)
Need decomposers to get back to inorganic compounds

6. Basic Characteristics of Ecosystems
At its simplest a community will have
At least one species that is a producer
Another species that is a decomposer
Plus a fluid medium

7. Ecological Communities
Ecological community defined in two ways
A set of interacting species found in the same place and functioning together to maintain life.
Operational def= all the species found in an area, whether or not they interact.

8. Food Chains
Energy, chemicals and some compounds are transferred from creature to creature along food chains (food webs).
The linkage of who feeds on whom
Grouped by trophic level
# of feeding levels away from original source of energy

9. Trophic Levels First trophic level Second trophic level
Use energy from the sun and carbon dioxide from the air to photosynthesizes
Green plants, algae and certain bacteria
Called autotrophs
Second trophic level
Organisms that feed on autotrophs
Called herbivores

10. Trophic Levels Third trophic level Forth trophic level
Feed directly on herbivores
Called carnivores (meat eaters)
Forth trophic level
Carnivores that feed on third-level carnivores
Decomposers- feed on waste and dead organisms of all trophic levels

12. A Terrestrial Food Chain
Example: North American Temperate Woodland
1st level- grasses, herbs and trees
2nd level- mice, pine borer and deer
3rd level- foxes, wolves, hawks and other predatory birds and insects
4th level- humans

14. An Oceanic Food Chain Tend to have more trophic levels
1st level- planktonic algae and planktonic bacteria
2nd level- zooplankton and some fish
3rd level- fish and invertebrates feed on herbivores, baleen whales
4th+ levels- killer whales, predatory fish

16. The Food Web of the Harp Seal
Food webs are complex because most species feed on several trophic levels.
Harp seal (shown at 5th level)
Feeds on flatfish (4th level)
But also feed on foods from 2nd – 4th
A species that feeds on several levels placed in a category one above the highest level it feeds on.

18. Community Level Interactions
Indirect and more complicated community wide affects species have on one another.
Sea otter of the Pacific Ocean
Came close to extinction because of over hunting for fur
Feed on shellfish (abalone, sea urchins)
Where sea otters abundant kelp beds abundant and few sea urchins
Otters affects the abundance of kelp

19. Community Level Interactions
Sea otters have community level effect
Where more kelp is present more habitat for many species
Keystone species
A species that has a large effect on its community or ecosystem
Holistic view
Ecological community is more than the sum of its parts

22. How do you know when you have found an ecosystem?
An ecosystem is the minimal entity that has the properties required to sustain life.
Vary greatly in structural complexity and clarity of their boundaries.
Differ is size, composition, proportion of non-biological constituents and degree of variation in time and space.

24. Watershed
Watershed
Commonly used practical delineation of the boundary of an ecosystem
Determined by topography
United in terms of chemical cycling

26. Ecosystem Management Ecosystem can be natural or artificial
Can also be managed
Agriculture
Wildlife preserves
Ecosystem concepts lies at the heart of the management of natural resources.