CHAPTER 5, SECTION 1 Energy Flow in Ecosystems
May 22, 2015
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.