ENERGY FLOW

• All living things need energy to survive• What is the source of that energy?

The Sun!

• Producers (or primary producers) use the sun’s energy to make food

• This process is called photosynthesis

• energy from light is

absorbed by proteins 

that contain green 

chlorophyll pigments

• Organisms that make their own food are called Autotrophs

• “Auto”=self “Troph”=feed

Plants

Some Bacteria

Moss

Algae

• Consumers cannot make their own food.• They must eat other organisms to get energy.

• Breaking down food to release the stored energy for use is called cellular respiration

• Organisms that use cellular respiration to get energy are called Heterotrophs.

• “Hetero”=other “Troph”=feed

Animals

Some Bacteria

Fungi

Food Chains and Food Webs• Primary consumers (herbivores) feed directly on

producers• Herbivores are organisms that eat plants or algae

• ex. Moose, cattle, grasshoppers, rabbits • Secondary consumers feed on primary consumers• Tertiary consumers feed on secondary consumers

• High-level consumers are usually carnivores• Carnivores are organisms that eat mainly meat

• ex. lions, polar bears, sharks

• Omnivores are organisms that eat both plants and meat (producers and consumers)• ex. humans, raccoons, most bears, most primates

• Food chains show the relationship of feeding and energy transfer in organisms of an ecosystem

• Many food chains become connected in a complex relationships called a food web

• Each step in a food chain is known as a trophic level

Energy moves up the trophic levels

• Detritivores eat dead organisms and waste• ex. earthworms, maggots

• Decomposers consume and break down dead organisms or waste matter into simple substances. • Send nutrients back into the soil• ex. mold, fungi

• Scavengers are carnivores that feed on dead animals• ex. vultures, hyenas, seagulls, ravens

• Pyramid of biomass shows the total amount (mass) of living material at each trophic level

• Only 10% of the energy received from food is stored in the body; 90% is used to run your organs

• Pyramid of energy shows the total amount of energy at each trophic level

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Photosynthesis

• The process of photosynthesis is a chemical reaction

• It is the most important chemical reaction on our planet!

• The process of changing light energy to chemical energy

• Energy stored as sugar• Occurs in plants and some algae• Takes place in the chloroplasts, using chlorophyll, the green pigment in plants

• Plants capture light energy and use that energy to make glucose (sugars)

• Sunlight provides the energy needed by chlorophyll to change molecules of carbon dioxide and water into glucose

• Oxygen is also released in this reaction

Why is it important to us?

• We cannot make our own food (glucose, energy), we must get our food from plants.

• Plants are the first step in the food chain.• The oxygen released during photosynthesis is necessary for all living things.

Cellular Respiration• The release of chemical energy for use by cells.• The breakdown of glucose molecules to release

energy

• Once the energy that was in sunlight is changed into chemical energy by photosynthesis, an organism has to transform the chemical energy into a form that can be used by the organism.

Energy Pyramid• Species in the highest trophic levels have less energy available to them than species near the bottom

• This often results on their populations being much smaller than species lower in the food chain (number of predators<herbivores)

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