Chapter 5.1Chapter 5.1Energy Flow in Ecosystems

Environmental ScienceSpring 2011

OjectivesOjectives

Describe how energy in transferred from the sun to producers and then to consumers

Describe one way in which consumers depend on producers

List two types of consumers Explain how energy transfer in a food web is

more complex than energy transfer in a food cycle

Explain why an energy pyramid is representation of trophic levels

Life Depends on the SunLife Depends on the Sun

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

Photosynthesis: solar drives a series of chemical reaction thatrequire carbon dioxideand water and produce sugars (carbohydrates).

Life Depends on the SunLife Depends on the Sun

Photosynthesis equatin:

Life Depends on the SunLife Depends on the Sun

Producer: organism that makes its own food◦Ex. Sunflower ◦Also called autotrophs

Consumers: organisms that get their energy from eating other organisms◦Ex. Deer, lion ◦Also called heterotrophs

All organisms get their energy directly or indirectly from the sun!

Life Depends on the SunLife Depends on the Sun

Producer or consumer? Autotroph or heterotroph?

An Exception: Deep-OceanAn Exception: Deep-Ocean

Large communities of worms, clams, crabs, mussels, and barnacles live near deep ocean vents

Exist in total darkness, photosynthesis can not occur

Where do they get energy:◦Bacteria live in some of the organisms and use

hydrogen sulfide to make their own food ◦Bacteria are producers◦Bacteria are eaten by the other underwater

organisms

What Eats What?What Eats What?

Herbivores: consumers that eat only producers ◦Ex. Rabbit, cow, sheep

Carnivores: eat only other consumers ◦Ex. Tiger, wolf, shark

What Eats What?What Eats What?

Omnivores: eat both plants and animals◦Ex. Humans, chimpanzees

Decomposers: consumers get their food by breaking down dead organisms ◦Ex. Bacteria, fungus

Cellular Respiration Cellular Respiration

Cellular Respiration: Process of breaking down food to yield energy◦Cells absorb oxygen and use it to release

energy from food

Cellular Respiration Cellular Respiration

Excess energy you obtain is stored as fat or sugar

All living things use cellular respiration to get the energy they need from food molecules◦Even organisms that make their own food

Energy TransferEnergy Transfer

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

Food chains, food webs, trophic levels ◦Trace transfer of energy

Food Chains and Food WebsFood Chains and Food Webs

Food Chain: a sequence in which energy is transferred from one organisms to the next as each organism eats another organism

Food Chains and Food WebsFood Chains and Food Webs

Food Webs: includes more organisms and multiple food chains linked together, shows many feeding relationships that are possible in an ecosystem

Trophic LevelsTrophic Levels

Trophic Level: each step through which energy is transferred in a food chain

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

About 90% of energy at each trophic level is used up, remaining 10% is all that is available to next trophic level

Trophic LevelsTrophic Levels

Energy PyramidsEnergy Pyramids

Each layer represents one tropic level Producers: at base, lowest trophic level,

contains most energy Herbivores: second level, contain less

energyCarnivores: third level, feed on

herbivores, contain less energyCarnivores that feed on carnivores:

highest level, contain less energy

Energy PyramidsEnergy Pyramids

Energy Loss in EcosystemsEnergy Loss in Ecosystems

Because so much energy is lost at each level, there are fewer organisms at the higher trophic levels ◦Ex. 1,000 zebras for every 1 lion on African

savannah ◦Must be enough herbivores to support

carnivores

Energy Loss in EcosytemsEnergy Loss in Ecosytems

Loss of energy from tropic level to trophic level limits the number of trophic levels in an ecosystem

Organisms that feed on organisms at the top trophic level are usually small, such as parasitic worms and fleas that require small amounts of energy