Section ObjectivesSection Objectives

• Trace the path of energy and matter in an ecosystem.

• Compare how organisms satisfy their nutritional needs.

The producers: AutotrophsThe producers: Autotrophs The ultimate source of the energy for life is The ultimate source of the energy for life is

the the sunsun..

Plants use the Plants use the sun’s energy to sun’s energy to manufacture manufacture food in a food in a process called process called photosynthesis.photosynthesis.

The producers: AutotrophsThe producers: Autotrophs

Other organisms in the biosphere depend on Other organisms in the biosphere depend on autotrophs for nutrients and energy. These autotrophs for nutrients and energy. These dependent organisms are called dependent organisms are called consumers.consumers.

An organism that uses light energy or energy An organism that uses light energy or energy stored in chemical compounds to make stored in chemical compounds to make energy-rich compounds is a producer, or energy-rich compounds is a producer, or autotrophautotroph..

The consumers: HeterotrophsThe consumers: Heterotrophs

An organism that cannot make its own food An organism that cannot make its own food and feeds on other organisms is called a and feeds on other organisms is called a heterotroph.heterotroph.

The consumers: HeterotrophsThe consumers: Heterotrophs

A heterotroph A heterotroph that feeds only on that feeds only on plants is an plants is an herbivore.herbivore.

The consumers: HeterotrophsThe consumers: Heterotrophs

Some Some heterotrophs eat heterotrophs eat other other heterotrophs. heterotrophs. Animals such as Animals such as lions that kill lions that kill and eat only and eat only other animals other animals are are carnivorescarnivores..

The consumers: HeterotrophsThe consumers: Heterotrophs ScavengersScavengers eat animals that have already died. eat animals that have already died.

The consumers: HeterotrophsThe consumers: Heterotrophs DecomposersDecomposers

break down the break down the complex complex compounds of compounds of dead and dead and decaying plants decaying plants and animals into and animals into simpler simpler molecules that molecules that can be more can be more easily absorbedeasily absorbed

•Bacteria and fungi, are decomposers.

Flow of Matter and Energy in EcosystemsFlow of Matter and Energy in Ecosystems

Autotrophs

First-order heterotrophs

Third-order heterotrophs Second-order

heterotrophs

Decomposers

Food chains: Pathways for matter and energyFood chains: Pathways for matter and energy

In a In a food chainfood chain, nutrients and energy move , nutrients and energy move from autotrophs to heterotrophs and, from autotrophs to heterotrophs and, eventually, to decomposers.eventually, to decomposers.

Food chains: Pathways for matter and energyFood chains: Pathways for matter and energy

A food chain is drawn using arrows to indicate A food chain is drawn using arrows to indicate the direction in which energy is transferred the direction in which energy is transferred from one organism to the next.from one organism to the next.

berries → mice → black bear

Food chains: Pathways for matter and energyFood chains: Pathways for matter and energy

A portion of the energy is given off A portion of the energy is given off as heatas heat at at each transfer.each transfer.

Each organism in a food chain represents a Each organism in a food chain represents a feeding step, or feeding step, or trophic level,trophic level, in the passage of in the passage of energy and materials.energy and materials.

Food websFood webs

A A food webfood web, shows all the possible feeding , shows all the possible feeding relationships at each trophic level in a relationships at each trophic level in a community.community.

Food websFood webs

Chihuahuan raven Honey mesquite (pods eaten by beetles)

Pronghorn antelope

Gambel quail

JackrabbitDesert tortoise

Prickly pear cactus

Long-tail weasel

Coyote (top carnivore)

Roadrunner

Kangaroo rat (seed eater)

ants

Texas horned lizard

Red spotted toad Mexican

whiptail lizard

Mojave rattlesnake

Energy and trophic levels: Ecological pyramidsEnergy and trophic levels: Ecological pyramids

The The basebase of the ecological pyramid represents of the ecological pyramid represents the autotrophs, or first trophic level. Higher the autotrophs, or first trophic level. Higher trophic levels are layered on top of one trophic levels are layered on top of one another.another.

Energy and trophic levels: Ecological pyramidsEnergy and trophic levels: Ecological pyramids The pyramid of The pyramid of

energy illustrates energy illustrates that the amount that the amount of available of available energy energy decreases at decreases at each succeeding each succeeding trophic level.trophic level.

Pyramid of Energy

Heat

Heat

Heat

Heat

0.1% Consumers

1% Consumers

10% Consumers

100% Producers

Parasites, scavengers, and

decomposers feed at each

level.

Energy and trophic levels: Ecological pyramidsEnergy and trophic levels: Ecological pyramids The total energy transfer from one trophic The total energy transfer from one trophic

level to the next is only about level to the next is only about ten percentten percent because organisms fail to capture and eat all because organisms fail to capture and eat all the food energy available and some of the the food energy available and some of the energy enters the environment as heat, but energy enters the environment as heat, but the total amount of energy remains the same.the total amount of energy remains the same.

Energy and trophic levels: Ecological pyramidsEnergy and trophic levels: Ecological pyramids

A pyramid of A pyramid of numbers shows numbers shows that population that population sizes decrease sizes decrease at each higher at each higher trophic level.trophic level.

Pyramid of Numbers

Fox (1)

Birds (25)

Grasshoppers (250)

Grasses (3000)

Energy and trophic levels: Ecological pyramidsEnergy and trophic levels: Ecological pyramids BiomassBiomass is the total is the total

weight of living weight of living matter at each matter at each trophic level. A trophic level. A pyramid of biomass pyramid of biomass represents the total represents the total weight of living weight of living material available at material available at each trophic level.each trophic level.

Pyramid of Biomass

1 kilogram of human tissue

10 kilograms of beef

100 kilograms of grain

Cycles in NatureCycles in Nature

Matter is cycledMatter is cycled and is and is not replenishednot replenished like like the energy from sunlight. There is a finite the energy from sunlight. There is a finite amount of matter.amount of matter.

The water cycleThe water cycle Water is constantly moving between the Water is constantly moving between the

atmosphere and Earth.atmosphere and Earth.

Precipitation

EvaporationRunoff

Groundwater

TranspirationEvaporation

Condensation

Oceans

The carbon cycleThe carbon cycle Carbon is the building block of the molecules Carbon is the building block of the molecules

of life (like proteins and sugars).of life (like proteins and sugars).

Organisms use these carbon molecules for Organisms use these carbon molecules for growth and energy.growth and energy.

The nitrogen cycleThe nitrogen cycle Nitrogen is converted from a gas to Nitrogen is converted from a gas to

compounds important for life and then back to compounds important for life and then back to a gas.a gas.

The phosphorus cycleThe phosphorus cycle In the phosphorus cycle, phosphorus moves In the phosphorus cycle, phosphorus moves

between the living and nonliving parts of the between the living and nonliving parts of the environment.environment.