Ecosystems movement of energy

Food chains and webs

LEARNING FOCUS

Introducing a new species may
disrupt the balance in an ecosystem

31

SUCCESS CRITERIA

✔ I can use a food web to determine
trophic levels of organisms

FOOD WEBS

ALL LIVING THINGS REQUIRE ENERGY

32

Living things can be broken up into three categories:

•Organisms that make their own food

•Organisms that eat other organisms

•Organisms that break down dead things

Source of energy

The Sun is our source of heat and light energy and is crucial to the continuation of life on Earth. Plants, algae and some plankton use energy from the Sun to help them make the food they need for life. This process is called photosynthesis. The main products of photosynthesis are simple sugars, such as glucose, and oxygen. Organisms that can carry out photosynthesis are called producers. 

All life on Earth depends on the Sun and producer organisms.

PRODUCERS

PRODUCES ARE PART OF THE FIRST TROPHIC
LEVEL

38

•Producers are organisms that make their

own food by using energy from the Sun.

•They do this by photosynthesising

•Plants, algae and other singled-celled

organisms are known as producers.

•Other organisms consume producers to gain

energy from them. Without producers, other

organisms would not be able to survive.

Consumers

All other organisms on Earth cannot make their own food to then make energy and therefore must eat other living things. These organisms are called consumers. Humans, grasshoppers, cows, monkeys, dogs, worms, frogs and snakes are examples of consumers. 

The diagram below is called a food chain. It shows the feeding relationships among four organisms. One organism provides food for the second; the second provides food for the third and so on.

​Decomposers

CONSUMER
S

39

Multiple Choice

What is a producer? 

• Organism that creates their own food.

• Organism that eat other organisms for energy

• Organism that eat other dead organisms

Multiple Choice

What is a consumer? 

• Organism that creates their own food.

• Organism that eat other organisms for energy

• Organism that eat other dead organisms

Multiple Choice

What is a decomposer? 

• Organism that creates their own food.

• Organism that eat other organisms for energy

• Organism that eat other dead organisms

FOOD CHAINS MAKE UP FOOD WEBS

34

FOOD
WEBS

FOOD WEBS INCORPORATE DIFFERENT FOOD
CHAINS

•Food chains and webs show the relationships between producers,
consumers and decomposers

•They are a visual way of showing who eats what.

•The direction of the flow of energy in a food chain is shown by
the direction of the arrow.

33

Remember:
The arrows point
to the organism
that is doing the
eating.

SIMMILARITIES:
•Both visual ways of showing
who eats what in an ecosystem.

DIFFERENCES:
•Food chains show one predator-prey
pathway.
•Food webs show more than one food
chain occurring at once.

Multiple Choice

What animal is on the top of the food chain? 
*Remember Humans are on the top of all food chains because we do not get hunted. 

• Grass

• Grasshopper

• Mouse

• Owl

Multiple Choice

Who does the owl get energy from? 

• Grass

• Grasshopper

• Mouse

• Ow

Multiple Choice

Who is the producer in this food chain? 

• Grass

• Grasshopper

• Mouse

• Ow

Multiple Choice

Who does the grasshopper get energy from? 

• Grass

• Grasshopper

• Mouse

• Ow

Multiple Choice

Which organism in this food chain is a secondary consumer?

• Fish

• Grass

• Grasshopper

• Hawk

Multiple Choice

Which organism in this food chain is a primary consumer?

• Fish

• Grass

• Grasshopper

• Hawk

TROPHIC LEVELS

•The trophic level of
an organism is the
position it occupies in
a food web.

•An energy pyramid is
another way to
show energy
flow from one trophic
level to another.

ENERGY
FLOW

ONLY 10% OF THE ENERGY IN ONE TROPHIC
LEVEL IS TRANSFERRED TO THE NEXT.

37

•The rest is lost to the environment as heat or waste products.

https://www.youtube.com/watch?v=T5XhbhqOL_c
https://www.youtube.com/watch?v=Tn0_L-8amjM

Multiple Choice

In this food pyramid, which level has the greatest amount of energy?

• Producers

• Primary Consumers

• Secondary Consumers

• Tertiary Consumers

Multiple Choice

How much energy is passed from one trophic level to the next?

• 1%

• 10%

• 50%

• 100%

Multiple Choice

In this food chain, the bacteria is most likely acting as a -

• predator

• competitor

• decomposer

• producer

Multiple Choice

each level of the food chain is called a ________ level.

• Food-eating

• Trophic

• Sunlight

• Energy

Multiple Choice

A series of interrelated food chains in a given ecosystem is called a ______________.

• trophic level

• food pyramid

• predator-prey relationship

• food web

Multiple Choice

All energy in ecosystems starts here:

• the producers

• the clouds

• the sun

• the consumers

Multiple Choice

A nonliving part of an ecosystem

• nonlimiting factor

• limiting factor

• biotic factor

• abiotic factor

Multiple Choice

The overlapping food chains in an ecosystem

• food chain

• food web

• decomposers

• producers