Botkin and Keller Environmental Science 5e

Chapter 6

Ecosystems and

Ecosystem Manageme

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Botkin and Keller Environmental Science 5e

Basic Characteristics of Ecosystems

• Sustained life on Earth is a characteristic of ecosystems, not of individual organisms or populations- no member of a community can carry out the processes of life alone

1) Structure: An ecosystem is made up of two major parts:

• Non-Living (Abiotic)- Physical Environment (Soil, Air and Water)

• Living (Biotic)- Ecological community

Botkin and Keller Environmental Science 5e

Basic Characteristics of Ecosystems

2) Processes: Two basic kinds of processes must occur in an ecosystem: a cycling of chemical elements and a flow of energy

3) Change: An ecosystem changes over time and can undergo development through a process called succession

Botkin and Keller Environmental Science 5e

Ecological Communities and Food Chains

Ecological Communities:1) A set of interacting species that occur in

the same place and function together to make possible the persistence of life

• Energy, chemical elements and some compounds are transferred from creature to creature along FOOD CHAINS/FOOD WEBS (Linkage of who feeds on whom)

Botkin and Keller Environmental Science 5e

Trophic Levels

• A trophic level consists of all those organisms in a food web that are the same number of feeding levels away from the original source of energy.

• The original source of energy in most ecosystems is The Sun.

Botkin and Keller Environmental Science 5e

Food Chains and Food Webs

• A Terrestrial Food Chain 4 trophic levels:

• Autotrophs (Photosynthesizing plants, algae and bacteria)

• Herbivores (Plant-Eaters)• Carnivores (Feed directly on Herbivores)• Carnivores (Feed on other Carnivores) and

Decomposers (Bacteria and Fungi-Feed on everything)

People are Omnivores (Herbivore & Carnivore)

Botkin and Keller Environmental Science 5e

Botkin and Keller Environmental Science 5e

Botkin and Keller Environmental Science 5e

The Community Effect

• Species interact directly and indirectly

• Community-level interactionsExample: Sea Otters of Pacific Ocean

• Otters eat Sea Urchins

• Sea Urchins eat kelp (important habitat for many creatures)

• More Sea Otters= Less Sea Urchins= More Kelp Forests for many sea creatures

Botkin and Keller Environmental Science 5e

Keystone Species

• A species such as the Sea Otter that has a large effect on its community or ecosystem is called a Keystone Species

• Removal or change in the role of a keystone species within the ecosystem changes the basic nature of the community

Botkin and Keller Environmental Science 5e

Community Interactions with Sea Otter

Botkin and Keller Environmental Science 5e

Oceanic Food Web

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Food Web of Harp Seal

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Natural and Artificial Ecosystems

• Ecosystems can be natural or artificial or a combination of both

• Agriculture can be thought of as partial management of certain kinds of ecosystems

• Wildlife Preserves are examples of partially managed ecosystems

Botkin and Keller Environmental Science 5e

Review Questions

• 1) What is the difference between an ecosystem and an ecological community?

• 2) In what ways would an increase in the number of sea otters and a change in their geographical distribution benefit fisherman? In what ways would these changes be a problem for fisherman?

Botkin and Keller Environmental Science 5e

Review Questions

• 3) Based on the discussion in this chapter, would you expect a highly polluted ecosystem to have many species or few species?

• 4) Is our species a keystone species? Explain.