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

Lesson 4/ ESRM 100 / University of Washington 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.

Lesson 4/ ESRM 100 / University of Washington How Populations Change Over Time 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

Lesson 4/ ESRM 100 / University of Washington The populations of wolves and moose change over time, even without human interference.

Lesson 4/ ESRM 100 / University of Washington American Chestnut Blight For more information, see "Chestnut Blight" and the Wikipedia article on Chestnut Blight.Chestnut BlightWikipedia article on Chestnut Blight

Lesson 4/ ESRM 100 / University of Washington Professions and Places: The Ecological 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

Lesson 4/ ESRM 100 / University of Washington Measuring Niches Can species share a niche? Two flatworm species: some streams have just one of the species, others have both Temperature is key

Lesson 4/ ESRM 100 / University of Washington How Species Coexist Flour Beetle Experiments In a uniform environment, one species always wins

Lesson 4/ ESRM 100 / University of Washington Two Examples of Symbiosis Elk-ruminant bacteria to digest cellulose Red alder – Frankia to fix Nitrogen from air

Lesson 4/ ESRM 100 / University of Washington The Community Effect – Sea Otter

Lesson 4/ ESRM 100 / University of Washington The Effect of Sea Otters on the Community

Lesson 4/ ESRM 100 / University of Washington The Ecosystem: Sustaining Life on 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.

Lesson 4/ ESRM 100 / University of Washington A Simple Ecosystem: Yellowstone Hot Spring

Lesson 4/ ESRM 100 / University of Washington A Food Web

Lesson 4/ ESRM 100 / University of Washington Food Webs Some food webs appear simple and neat.

Lesson 4/ ESRM 100 / University of Washington Food Web of the Harp Seal In reality, many food webs are complex because most creatures feed on several trophic levels.

Lesson 4/ ESRM 100 / University of Washington Ecosystem Energy Flow Energy is the ability to do work, and to move matter through an ecosystem.

Lesson 4/ ESRM 100 / University of Washington 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?

Lesson 4/ ESRM 100 / University of Washington 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

Lesson 4/ ESRM 100 / University of Washington 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

Lesson 4/ ESRM 100 / University of Washington 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

Lesson 4/ ESRM 100 / University of Washington 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.

Lesson 4/ ESRM 100 / University of Washington 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.

Lesson 4/ ESRM 100 / University of Washington 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.

Chapter 4: Ecosystems Question? your TA.