Chapter 2 – Principles of

Ecology

2.2 Flow of Energy in an Ecosystem

Vocabulary Listautotroph

heterotrophherbivorecarnivoreomnivoredetritivore

trophic levelfood chainfood webbiomass

• One way to study the interactions within an ecosystem is to trace how energy flows through the system.

• All organisms are classified by the way they obtain energy.

Energy in Ecosystems

• Organisms that capture energy from sunlight or inorganic substances (CO2, H2O, H2S) to produce food/energy available for all other organisms in the ecosystem.

Autotrophs

• They are called PRIMARY PRODUCERS• All green plants and bacteria

Autotrophs

• an organism that obtains energy by consuming other organisms

Heterotrophs (Consumers)

• A heterotroph that consumes only plants

Heterotrophs - Herbivore

• Heterotrophs that prey on other heterotrophs

Heterotrophs - Carnivore

• Heterotrophs that consumes plants AND prey on other heterotrophs

Heterotrophs - Omnivore

• Decompose organic materials in an ecosystem

Heterotrophs - Detritivores

• They feed on animals that have died:1. Without them, the biosphere would be littered

with dead organisms.2. Return nutrients (from dead matter) to the soil,

air, and water where they become available for use by other organisms.

How Do Detritivors Help An Ecosystem?

• Ecologists use food chains and food webs to describe the flow of energy

• Each step in a food chain or food web is called a trophic level

Models of Energy Flow

• Autotrophs = first trophic level in all ecosystems (produce their own food).

• Heterotrophs = the remaining levels (get energy from the trophic level before it)

Models of Energy Flow

• A simple model that shows how energy flows through an ecosystem

• Each organism gets energy from the organism it eats. • The flow of energy is always one way: into the consumer• The energy can be used to build new cells/tissues or to be

released into the environment

Food Chains

Food Webs• Most organisms feed on more than one species. • A food web is a model that shows all the possible

feeding relationships in an ecosystem. • give a more accurate picture of how energy flows in an

ecosystem

Principles of EcologyChapter

• Use a handout with pictures

Ecological Pyramids

Ecologists use ecological pyramids to model how energy flows through ecosystems in three different ways.

Each level of the pyramid represents a trophic level.

A Pyramid Of Energy

indicates the amount of energy available to each trophic level. • About 90 % of the available energy is used by the organisms at each

level. • About 10 % available to the next level of the pyramid.

A pyramid of biomass

Biomass = total mass of living matter at each trophic • Each level shows the amount of biomass consumed by the

level above it

A Pyramid Of Numbers

• Shows the number of organisms consumed at each trophic level in an ecosystem.

• The number decreases at each level because less energy is available to support organisms.

CLASSWORK/HOMEWORK

2.2 Reading Notes2.2 Study GuideMiniLAB: Construct a Food WebVirtual lab: http://connected.mcgraw-

hill.com/media/repository/protected_content/COMPOUND/50000035/27/47/BL_03/player.html

NO 2.2 QUIZ

1) How does wavelength impact a biome2) How does a type of soil impact a biome3) How does wind impact a biome4) How does CO2 level affect impact a biome

Possible Biomes and Abiotic Factors