Chapter 5: EnergyPart 1: Food Chains, Food Webs, and the Transfer of

Energy

Autotrophs• An organism capable of making its

own organic substances from inorganic compounds

• Also called Producers

• Without autotrophs, there would be no life on this planet

A group of organisms that can change light energy into chemical energy (glucose) – Photosynthesis!– Example: green plants, algae, cyanobacteria

PhotoautotrophsThere are 2 types of autotrophs: The first type is the…

Photoautotrophs

Chemoautotrophs

Autotrophs that get their energy from inorganic substances, such as sulfur• Live deep down in the ocean where there

is no sunlight• Ex. Some bacteria

The second type of autotrophs are the …

Heterotrophs• Organisms that do not make their own food

(needs to eat)

• Another term for Heterotroph is Consumer because they consume other organisms in order to live. Heterotrophs give off carbon dioxide, which is required for green plants in photosynthesis

Ex. Rabbits, Deer, Mushrooms

Heterotrophs

Heterotrophs: Herbivores

1st Order Consumer = Herbivore Herbivores – eat ONLY plants

Ex. – Cows, Elephants, Giraffes

Heterotrophs

2nd Order ConsumerThey are carnivores (eat

meat)Eats first order consumersEx. – Lions, Tigers, Sharks

Heterotrophs

3rd Order Consumereats 2nd order consumers

4th Order Consumereats 3rd order consumers

Heterotrophs: Omnivores

Omnivores – eat BOTH plants and animals Ex. – Bears and Humans

Heterotrophs: Scavengers

Scavengers – feed on the tissue of dead organisms (both plants and animals)

Ex. – Vultures, Crows, and Shrimp

Heterotrophs: Decomposers

Decomposers – absorb any dead material and break it down into simple nutrients or fertilizers

Ex. – Bacteria and Fungi (such as mushrooms

Ok, now that we know the words…

Let’s put them together to show the flow of energy through the ecosystem …

Food web video

Transfer of Energy

When a zebra eats the grass, it does not obtain all of the energy the grass has (much of it is not eaten)

When a lion eats a zebra, it does not get all of the energy from the zebra (much of it is lost as heat)

Transfer of Energy

No organism EVER receives all of the energy from the organism they just ate

Only 10% of the energy from one trophic level is transferred to the next – this is called the 10% law

Trophic level = energy level (each step of the food chain is a trophic level)

Transfer of Energy: The 10% Rule

– Who eats who in the food chain– Steps along which materials & energy pass

The 10% Rule

Food Chains

The energy flow from one trophic level to the other is known as a food chain

It involves one organism at each trophic level

Food Chain

Identify:

Source of the energyProducerHerbivoreCarnivore

Food Chain

Identify:

Source of the energyProducerHerbivoreCarnivores1st order consumer2nd order consumer3rd order consumer

Food Web

• Food Web – all of the feeding relationships in an ecosystem

• Food webs are more complex and involve lots of organisms

Food Web

Food Web

Notice the direction the arrow points The arrow points in the direction of the energy transfer, NOT “what ate what”

Marine Food Web

Ecological Pyramids

4th order consumers

3rd order consumers

2nd order consumers

1st order consumers (herbivores)Producers

Ecological Pyramid

• An ecological pyramid shows the relationship between consumers and producers at different trophic levels in an ecosystem

• Shows the relative amounts of energy or matter contained at each trophic level

• The Pyramid shows which level has the most energy and the highest number of organisms

Ecological Pyramids

Illustrates:Food Chain

of numbersof biomassof energy

Pyramid of Numbers

Biomass

• The total mass of the organic matter at each trophic level is called biomass

• Biomass is just another term for potential energy – energy that is to be eaten and used.

• The transfer of energy from one level to another is very inefficient (10% Law)

Pyramid of Biomass

Energy Pyramid

Which level has the most energy?Which level has the most organisms?Which level has the least organisms?Which level has the least energy?