Calculating Energy Transfer in Food Webs and Pyramids

Food Chains, Food Webs, and Energy Pyramids

By Kate Harnage

Food Chains

• Definition: The pathway that energy and nutrients can follow through an ecosystem.

• Producers make up the (biggest) first level.

• Herbivores (primary consumers) make up the next level.

• Ominivores and Carnivores (secondary consumers) follow.

• Tertiary Consumers top the pyramid.

• Decomposers?????

Food Webs

• Definition: An interconnected food chain model that shows how energy flows through an ecosystem.

• Arrows show the direction of energy flow FROM one organism TO another.

• Obviously, all energy paths BEGIN at the CONSUMER level.

Second trophic level

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​Herbivores = only eat plants

Primary consumer

​​Secondary consumer

​Fourth trophic level

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Carnivores or Omnivore

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Predator or Scavenger​

Tertiary consumers

​Third tropic level​

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Carnivores = only eat animals

Omnivores = eat plants and animals​

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Predator or Scavenger​

90% of energy is lost with each trophic level.

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They show:

• the amount of energy decreases for higher consumers

• a large number of producers are needed to support an​ ecosystem.

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​Energy Pyramids

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Energy Pyramids

When an organism obtains energy, most of it is used to conduct life processes. A little of it is given off as heat, and a small amount is stored inside the body of the organism. This is how carnivores get energy.

There is less energy available at each level as you go up.

Multiple Choice

In what level of an energy pyramid is there the GREATEST amount of energy?

• Tertiary Level

• Secondary Consumer Level

• Primary Consumer Level

• Producer Level

Multiple Choice

What is the difference between food chains and food webs?

• Food chains show a single energy pathways, while food webs show several energy pathways

• Food web show multiple energy pathways, while food chains show only one energy pathway

Poll

How much energy do you think is passed to the consumer when they eat food?

• 100%

• 90%

• 75%

• 10%

Multiple Choice

A person who eats a chicken which feeds on grains is considered what type of consumer?

• producer

• primary consumer

• secondary consumer

• tertiary consumer

Multiple Choice

An organism that feeds on animals that are already dead is called a...

• producer

• consumer

• scavenger

• none of the above

Multiple Choice

What real life situation can affect food webs?

• Wildfires burning an ecosystem down

• People eating a lot

• Not watering plants

• Nothing can affect it

Multiple Choice

What would happen if there were no thrush in the model above?

• there would be more insects and slugs

• there would be less insects and sluga

• there would be more voles

• there would be more hawks

Multiple Choice

What is the producer in the picture above?

• grasshopper

• snake

• grass

• Sun

Levels of Organization Continued

• Population- A group of the same species living in the same place

• Community - all the LIVING things in an area interacting together

• Ecosystem - All the Living and Nonliving things in an area interacting
  

Multiple Choice

which is the correct order of the levels of organization from simple to complex?

• organism, population, community, ecosystem
• ecosystem, community, population, organism

Multiple Choice

Temperature, light, air, water, and soil are all  _____  parts of the environment

• alive
• biotic 
• abiotic
• living

Multiple Choice

Which of the following is not an abiotic factor?

• sun
• temperature
• soil
• grass

Multiple Choice

All of the living and nonliving things in an area that interact with each other are called a/an ______.

• community
• habitat
• population
• ecosystem

Multiple Choice

Where does the food chain START?

• with consumers that eat grass

• with the sun giving energy to producers

• with the sun giving energy to consumers

• with consumers eating other consumers

Multiple Choice

A Great White Shark would be found in what ecosystem?

• Freshwater

• Marine

• Terrestrial