G9 Chap 2.2 - Flow of Energy in an Ecosystem

How organisms get energy

Autotroph (Producer)

○Use energy from the Sun to produce energy in the form of sugar (food)

○Plants, algae

Heterotroph (Consumer)

○Consume other organisms to get energy

○Herbivore

■ only eats plants

○Omnivore

■eats plants and animals

○Carnivore

■only eats animals

How organisms get energy

Heterotroph (continued..)

●Detritivore - worms, insects

○Eat dead plant and animal material

●Decomposer - fungi, bacteria

○Absorbs nutrients from dead plants and animals

Both return leftover nutrients to the soil, water or air

●Without them, dead material would build up all over Earth

​Videos

​Energy Flow in Ecosystems

https://www.youtube.com/watch?v=LnPRHcp5_vo​

​

Classifying Organisms

https://www.youtube.com/watch?v=AHCOzc143Ec​

​

Decomposers​

https://www.youtube.com/watch?v=uB61rfeeAsM​

Multiple Choice

Which organism is an autotroph?

Multiple Choice

Which heterotroph eats only other animals?

• herbivore

• carnivore

• detritrivore

• decomposer

Multiple Choice

Which heterotroph eats only plants?

• herbivore

• carnivore

• omnivore

• decomposer

Multiple Choice

Most humans are which type of heterotroph?

• omnivore

• detritivore

• autotroph

• decomposer

Multiple Choice

What does a decomposer consume?

• living plants

• living animals

• dead plants and animals

• sunlight

Models for Energy Flow

Different ways to represent the flow of energy in an ecosystem

●Food chain

●Food web

●Ecological Pyramid

Each step is called a trophic level

●Autotrophs are always the first level

●Heterotrophs make up the other levels

○Each heterotroph gets its energy from the level below

Each organism uses some of the energy it eats for cellular processes

●Making new cells, moving, breathing

Some energy is released into the air as heat

Food Chain

Simple model

●Arrows show the one-way energy
flow

○The arrow points towards the
direction of energy flow

Food Web

Complex model

●More accurate of real life relationships

○Combination of many food chains

●Most organisms eat more than one
species

Ecological Pyramid

Can show either 1) Amount of energy, 2) Biomass or 3) Number
of Organisms at each trophic level
●Only 10% of energy is transferred to level above

●Amount of biomass decreases with each level
○Biomass = total mass of living organisms

●Numbers of organisms decreases with each level

(Pictures on next slide)

​Videos

​Food Chains

​https://www.youtube.com/watch?v=MuKs9o1s8h8

​

Food Webs and Energy Pyramids​

https://www.youtube.com/watch?v=-oVavgmveyY​

​

Multiple Choice

Which energy model is the best to show the relationships in the real world?

• food chain

• food web

• autotroph chain

• heterotroph pyramid

Multiple Choice

How much energy is transferred to the trophic level above?

• 1%

• 10%

• 100%

• 1000%

Multiple Choice

Which type of organism is always at the bottom of an energy model?

• autotroph

• heterotroph

• carnoivore

• herbivore