Energy in Ecosystems

• Producers– Basis of an ecosystem’s energy– Autotrophs: perform

photosynthesis to make sugars– Chemotrophs: Bacteria which

use minerals from deep-sea vents to make energy

• Consumers– Heterotrophs: Consumes

others for energy– Omnivores, herbivores,

carnivores, decomposers, detritivores

• Defined: Feeding level of an ecosystem

• Trophic levels consist of producers, consumers, and decomposers

• ~ 10% of energy is passed to the next level– ~ 90% is used by the organism or lost

as heat• If there are 45, 897 kcal at the primary

producer trophic level, how much energy is available to the other trophic levels?

– Food chains contain few trophic levels45,897 kcal

4589.7 kcal

458.97 kcal

45.897 kcal

4.5897 kcal

• 1st trophic level = Producers• Autotrophs (perform photosynthesis)• Bottom (basis) of food chain• Ex: Plants, algae, cyanobacteria

• 2nd trophic level = Primary consumers• Feed on producers• Herbivores (plant eaters)

• 3rd trophic level = Secondary consumers• Feed on primary consumers• Omnivores and carnivores

• 4th trophic level = Tertiary consumers• Feed on secondary consumers• Omnivores and carnivores

• 5th trophic level = Quaternary consumers• Feed on Tertiary consumers• Omnivores and carnivores

• Rarely shown on food chains

• Feed on any food chain level when organisms die

• Detritivores: Feed/ingest dead matter

• Decomposers: secrete enzymes to break down dead matter and then absorb the nutrients

What’s wrong with this food chain?The arrows are pointing the wrong direction.

This implies that the plant eats the grasshopper.

Food Chain Analysis

What’s wrong with this food chain?The arrows are pointing the wrong direction.

This implies that the grasshopper eats the mouse.

What’s wrong with this food chain?The arrows are pointing the wrong direction.

This implies that the mouse eats the snake.

What’s wrong with this food chain?The arrows are pointing the wrong direction.

This implies that the snake eats the hawk.

On your paper fix the arrows so they show the correct direction

energy travels…

Now the arrows show the direction that energy is passed up the food chain.

• Defined: diagram that compares energy used by producers & other organisms on trophic levels.

• Label the tropic levels in this energy pyramid

Defined: Group of interrelated food chainsArrows show direction energy (nutrients) travel

AnalysisTrace 2 food chains from this food web.

Defined: Group of interrelated food

chainsArrows show direction

energy (nutrients) travel

producer

Primary consumer

Secondary consumer

Tertiary consumer

Analysis:Highlight a food chain from this food web. Then label each trophic level.

producer

Primary consumer

Secondary consumer

Tertiary consumer

Quaternary consumer

Analysis:Highlight a food chain from this food web. Then label each trophic level.

Analysis• What could

happen if the grasshoppers die out due to pesticide use?

Spider death (no more

grasshoppers to eat)

Blue jay death (less spiders to eat)

Squirrel increase (less owls hunting them)

Owl death (less blue jays to eat)

YouTube Food Chain Video

Review1. How many trophic levels are in the following food chain?

Apple tree Worms Blue Jay Owl

2. If the tree in the example above makes 15,000 calories of energy from photosynthesis, how much energy is available for each other trophic level?

3. In the food chain above, which is the producer?4. In the food chain above, which is the primary consumer?5. In the food chain above, which is the tertiary consumer?6. Which level consumer are herbivores known as?7. What is the lowest consumer level possible for a carnivore?8. Examine the food web on the previous slides. Find a complete food

chain that is 6 trophic levels from start to finish.9. Why do food chains contain few trophic levels?

Review Answers1. How many trophic levels are in the following food chain? Four

Apple tree Worms Blue Jay OwlPrimary Producer, Primary Consumer, Secondary Consumer, Tertiary Consumer

2. If the tree in the example above makes 15,000 calories of energy from photosynthesis, how much energy is available for each other trophic level?Primary Producer, Primary Consumer, Secondary Consumer, Tertiary Consumer

1500 kcal 150 kcal 15 kcal3. In the food chain above, which is the producer? Apple Tree4. In the food chain above, which is the primary consumer? Worms5. In the food chain above, which is the tertiary consumer? Owl6. Which level consumer are herbivores known as? Primary Consumer7. What is the lowest consumer level possible for a carnivore?

Secondary Consumer

8. Examine the food web on the previous slides. Find a complete food chain that is 6 trophic levels from start to finish.Grass, Grasshopper, Spider, Blue Jay, Cat or Owl, Hawk

9. Why do food chains contain few trophic levels? Because only ~ 10% of energy is passed from one trophic level to the next, the longer the food chain, the more energy is lost overall. Less energy means there are less resources for the organisms in a particular trophic level.