CHAPTER 5 , SECTION 1

Energy Flow in Ecosystems

Life Depends on the Sun

Energy from the sun enters an ecosystem when a plant uses sunlight to make sugar molecules.

Photosynthesis Plants, algae, some bacteria capture solar energy. Solar energy powers a series of reactions that require

carbon dioxide and water. Sugar molecules (carbohydrates) are produced. Carbohydrates provide the energy that organisms

need to carry out daily activities. As organisms consume food and use energy, the

energy travels from one organism to another.

Photosynthesis

Life Depends on the Sun

Producers (Autotrophs) – Organisms that make their own food. Plants, algae, some bacteria

Consumers (Heterotrophs) – Organisms that get energy by eating other organisms. Humans, coyotes, cats, cows,

Deep-Ocean Ecosystems Total darkness Bacteria use Hydrogen Sulfide (H2S) to make their

own food. H2S comes from the hot water that escapes the cracks

in the ocean floor. The bacteria are then eaten by consumers.

What Eats What

Organisms can be classified by what they eat.

Types of Consumers: Herbivores Carnivores Omnivores Decomposers

Table 1, Page 127

Fig. 3-10, p. 57

SunOxygen (O2)

Carbon dioxide (CO2)

Secondary consumer(fox)

Soil decomposers

Primaryconsumer(rabbit)

PrecipitationFalling

leaves and twigs

Producer

Producers

Water

Scavengers

Powder broken down by decomposers into plant nutrients

in soil

Bark beetle engraving

Decomposers

Long-horned beetle holes

Carpenter ant

galleries

Termite and

carpenter ant work Dry rot

fungus

Wood reduced to powder

Mushroom

Time progression

Cellular Respiration

Organisms break down food to yield energy.Cellular Respiration

Occurs inside cells of organisms Cells absorb oxygen and use it to release energy from

food Cellular Respiration is the reverse of photosynthesis Sugar and oxygen combine to yield carbon dioxide,

water, and energy.

Cellular Respiration

Energy Transfer

Each time one organism eats another organism, a transfer of energy occurs.

Food chains, food webs, and trophic levels tell us how energy is transferred and how much energy is transferred.

Studying the paths of energy between organisms can tell us which organisms in an ecosystem depend on other organisms to survive.

Food Chains, Food Webs, Trophic Levels

Food Chain – A sequence in which energy is transferred from one organism to the next as each organism eats another organism.

Food Web – Includes many organisms and multiple food chains linked together.

Trophic Levels – Each step through which energy is transferred in a food chain or web.

Heat

Heat

Heat

Heat

Heat

Heat Heat Heat

Detritivores (decomposers and detritus

feeders)

First Trophic Level

Second TrophicLevel

Third Trophic Level

Fourth Trophic Level

Solar energy

Producers(plants)

Primary consumers

(herbivores)

Secondary consumers

(carnivores)

Tertiary consumers

(top carnivores)

HumansBlue whale Sperm whale

Crabeater seal

Elephant seal

Killer whale

Leopard seal

Adelie penguins Emperor

penguin

Petrel FishSquid

Carnivorous plankton

Krill Herbivorous plankton

Phytoplankton

Energy Loss in an Ecosystem

Each time energy is transferred from one organism to another, some of the energy is lost as heat and less energy is available to organisms at the next trophic level.

About 90% of the energy at each trophic level is used for life functions.

The remaining 10% of the energy becomes part of the organism’s body and is stored in its molecules.

The stored 10% is all that is available to the next trophic level when one organism consumes another organism.

Trophic Levels

Energy Loss in an Ecosystem

The Loss of Energy…

Means there are fewer organisms at each level.

Limits the number of trophic levels in an ecosystem

Summary Questions

1. Describe how energy is transferred from one organism to another. Give examples.

2. Describe the role that producers play in an ecosystem. What would happen if the producers became extinct?

3. Define and give examples of herbivore, carnivore, and omnivore.

4. Compare energy transfer in a food chain to energy transfer in a food web.

5. Could more people be supported by 20 acres of land if they only ate plants instead of both plants and animals. Explain your answer.