Lesson 4: Ecosystems

1. Lesson 4: Ecosystems Big Question: What Is Necessary to Sustain Life on Earth?

2. Lesson Goals After reading Chapter 4 and hearing/reading this lesson, you should be able to explain why the ecosystem is the basic system that supports life and enables it to persist; what food chains, food webs, and trophic levels are; how energy enters ecosystems and determines biological productivity; what a community-level effect is; what ecosystem management involves; and how conservation and management of the environment might be improved through ecosystem management.

3. How Populations Change OverTime and Interact with Each Other How and why does the abundance of a species change even without human influence? Interactions include competition, symbiosis, and predation/parasitism Would nature remain in balance if we didn’t interfere? Long term study of wolves and moose of Isle Royale National Park, Michigan

4. The populations of wolves and moose change over time, even without human interference.

5. American Chestnut Blight For more information, see "Chestnut Blight" and the Wikipedia article on Chestnut Blight.

6. Professions and Places: TheEcological Niche and the Habitat What is a habitat, and what is a niche? Where a species lives is its habitat What it does for a living (its profession) is its ecological niche Will a change in land use affect a species’ niche? A species’ habitat may be damaged to the point where its niche requirements are no longer available

7. Measuring Niches Can species share a niche? Two flatworm species: some streams have just one of the species, others have both Temperature is key

8. How Species Coexist Flour Beetle Experiments In a uniform environment, one species always wins

9. Two Examples of Symbiosis Elk-ruminant bacteria to digest cellulose Red alder – Frankia to fix Nitrogen from air

10. The Community Effect – Sea Otter

11. The Effect of Sea Otters on the Community

12. The Ecosystem: Sustaining Lifeon Earth The oldest fossils are more than 3.5 billion years old Ecosystems are crucial to sustaining life An ecosystem is comprised of the individuals of various species and their nonliving environment.

13. A Simple Ecosystem: Yellowstone Hot Spring

14. A Food Web

15. Food Webs Some food webs appear simple and neat.

16. Food Web of the Harp Seal In reality, many food webs are complex because most creatures feed on several trophic levels.

17. Ecosystem Energy Flow Energy is the ability to do work, and to move matter through an ecosystem.

18. Life and the Laws of Thermodynamics The law of conservation of energy: energy is neither created nor destroyed but merely changed from one form to another Why can’t the same energy continually cycle through an ecosystem?

19. The Law of Entropy The law of entropy: energy always changes from a more useful, more highly organized form to a less useful, disorganized form Whenever useful work is done, heat is released to the environment and that energy can never be recycled The net flow of energy through an ecosystem is a one-way flow

20. Producing New Organic Matter Primary production: Some organisms make their own organic matter from a source of energy and inorganic compounds Autotrophs: include green plants, algae, some bacteria Secondary production: Other organisms cannot make their own organic compounds from inorganic ones and must feed on other living things Heterotrophs: all animals, fungi, most bacteria

21. Respiration Living things use energy from organic matter through respiration Organic compound are combined with oxygen to release energy and produce carbon dioxide and water Involves organic chemicals called enzymes

22. Gross and Net Production Autotroph production involves • producing organic matter within the body--gross production; • using some of this new organic matter as a fuel in respiration; and • storing some of the newly produced organic matter for future use--net production. Most primary production takes place through photosynthesis.

23. Practical Implication I: Human Domination of Ecosystems Human domination is not yet a global catastrophe, although serious environmental degradation has resulted. Earth’s ecological and biological resources have been and will continue to be greatly modified by human use of the environment An important human-induced alteration of Earth’s ecosystems is land modification We can act to cause less damage.

24. Practical Implication II:Ecosystem Management Ecosystems can be natural or artificial or a combination of both. The ecosystem concept is central to management of natural resources. We must focus on their ecosystem and make sure that it continues to function.

25. Chapter 4: Ecosystems Question? E-mail your TA. eschelp@u.washington.edu