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

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 OverTime and Interact with Each OtherHow 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.

Lesson 4/ ESRM 100 / University of Washington

Professions and Places: TheEcological Niche and the HabitatWhat 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 Lifeon EarthThe 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 ThermodynamicsThe 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 EcosystemsHuman 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 ManagementEcosystems 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? E-mail your TA. [email protected]