Introduction to EcologyChapter 18
Table of Contents
Section 1 Introduction to Ecology
Section 2 Ecology of Organisms
Section 3 Energy Transfer
Section 4 Ecosystem Recycling
Section 1 Introduction to EcologyChapter 18
Objectives
• Identify a key theme in ecology.
• Describe an example showing the effects of interdependence upon organisms in their environment.
• Identify the importance of models to ecology.
• State the five different levels of organization at which ecology can be studied.
Section 1 Introduction to EcologyChapter 18
Interdependence: A Key Theme in Ecology
• Organisms and Their Environments– Species interact with both other species and their
nonliving environment.– Interdependence is a theme in ecology—one
change can affect all species in an ecosystem.
Section 1 Introduction to EcologyChapter 18
Ecological Models
• Ecological models help to explain the environment.
Chapter 18
Making an Ecosystem Model
Section 1 Introduction to Ecology
Section 1 Introduction to EcologyChapter 18
Levels of Organization
• Ecologists recognize a hierarchy of organization in the environment: biosphere, ecosystem, community, population, and organism.
Chapter 18
Levels of Organization
Section 1 Introduction to Ecology
Section 1 Introduction to EcologyChapter 18
Levels of Organization, continued
• The Biosphere– The broadest, most inclusive level of organization
is the biosphere, the volume of Earth and its atmosphere that supports life.
Section 1 Introduction to EcologyChapter 18
Levels of Organization, continued
• Ecosystems– The biosphere is composed of smaller units called
ecosystems. – An ecosystem includes all of the organisms and
the nonliving environment found in a particular place.
Section 1 Introduction to EcologyChapter 18
Levels of Organization, continued
• Communities, Populations, and Organisms– A community is all the interacting organisms
living in an area. – Below the community level of organization is the
population level, where the focus is on the individual organisms of a single species.
Section 2 Ecology of OrganismsChapter 18
Objectives
• Compare abiotic factors with biotic factors, and list two examples of each.
• Describe two mechanisms that allow organisms to survive in a changing environment.
• Explain the concept of the niche.
Section 2 Ecology of OrganismsChapter 18
Ecosystem Components
• Biotic and Abiotic Factors– Both biotic, or living, factors and abiotic, or
nonliving, factors influence organisms. Examples of abiotic factors are climate, sunlight, and pH.
Chapter 18
Click below to watch the Visual Concept.
Visual Concept
Comparing Biotic and Abiotic Factors
Section 2 Ecology of Organisms
Section 2 Ecology of OrganismsChapter 18
Organisms in a Changing Environment
• Acclimation– Some organisms can adjust their tolerance to
abiotic factors through the process of acclimation.
Section 2 Ecology of OrganismsChapter 18
Organisms in a Changing Environment, continued
• Control of Internal Conditions– Conformers are organisms that do not regulate
their internal conditions; they change as their external environment changes.
– Regulators use energy to control some of their internal conditions.
Section 2 Ecology of OrganismsChapter 18
Organisms in a Changing Environment, continued
• Escape from Unsuitable Conditions– Some species survive unfavorable environmental
conditions by becoming dormant or by migrating.
Section 2 Ecology of OrganismsChapter 18
The Niche
• A niche is a way of life, or a role in an ecosystem.
Chapter 18
Click below to watch the Visual Concept.
Visual Concept
Niche
Section 2 Ecology of Organisms
Section 3 Energy TransferChapter 18
Objectives
• Summarize the role of producers in an ecosystem.
• Identify several kinds of consumers in an ecosystem.
• Explain the important role of decomposers in an ecosystem.
• Compare the concept of a food chain with that of a food web.
• Explain why ecosystems usually contain only a few trophic levels.
Section 3 Energy TransferChapter 18
Producers
• Most producers are photosynthetic and make carbohydrates by using energy from the sun.
Section 3 Energy TransferChapter 18
Producers, continued
• Measuring Productivity– Gross primary productivity is the rate at which
producers in an ecosystem capture the energy of sunlight by producing organic compounds.
– The rate at which biomass accumulates is called net primary productivity.
Section 3 Energy TransferChapter 18
Consumers
• Consumers obtain energy by eating other organisms and include herbivores, omnivores, carnivores, detritivores, and decomposers.
Chapter 18
Click below to watch the Visual Concept.
Visual Concept
Comparing Consumers and Producers
Section 3 Energy Transfer
Section 3 Energy TransferChapter 18
Energy Flow
• Food Chains and Food Webs– A single pathway of energy transfer is a food
chain. – A network showing all paths of energy transfer is a
food web.
Chapter 18
Food Chain in an Antarctic Ecosystem
Section 3 Energy Transfer
Chapter 18
Food Web in an Antarctic Ecosystem
Section 3 Energy Transfer
Section 3 Energy TransferChapter 18
Energy Flow, continued
• Energy Transfer– Ecosystems contain only a few trophic levels
because there is a low rate of energy transfer between each level.
Chapter 18
Energy Transfer Through Trophic Levels
Section 3 Energy Transfer
Section 4 Ecosystem RecyclingChapter 18
Objectives
• List four major biogeochemical cycles.
• Summarize three important processes in the water cycle.
• Outline the major steps in the carbon cycle.
• Describe the role of decomposers in the nitrogen cycle.
• Summarize the major steps of the phosphorus cycle.
Section 4 Ecosystem RecyclingChapter 18
The Water Cycle
• Key processes in the water cycle are evaporation, transpiration, and precipitation.
Chapter 18
Water Cycle
Section 4 Ecosystem Recycling
Chapter 18
Click below to watch the Visual Concept.
Visual Concept
Water Cycle
Section 4 Ecosystem Recycling
Section 4 Ecosystem RecyclingChapter 18
The Carbon Cycle
• Photosynthesis and cellular respiration are the two main steps in the carbon cycle.
Chapter 18Section 4 Ecosystem Recycling
Carbon Cycle
Chapter 18
Click below to watch the Visual Concept.
Visual Concept
Carbon Cycle
Section 4 Ecosystem Recycling
Section 4 Ecosystem RecyclingChapter 18
Nitrogen Cycle
• Nitrogen-fixing bacteria are important in the nitrogen cycle because they change nitrogen gas into a usable form of nitrogen for plants.
Chapter 18
Nitrogen Cycle
Section 4 Ecosystem Recycling
Chapter 18
Click below to watch the Visual Concept.
Visual Concept
Nitrogen Cycle
Section 4 Ecosystem Recycling
Section 4 Ecosystem RecyclingChapter 18
Phosphorus Cycle
• In the phosphorus cycle, phosphorus moves from phosphate deposited in rock, to the soil, to living organisms, and finally to the ocean.