FOOD CHAINS
FOOD WEBS
ECOLOGICAL PYRAMIDS
October 22, 2014
Miss Mathieu
Who eats
whom or
what?
FOOD CHAINS
Grass
Rabbit
Fox
 Food chains show:
 What eats what
 How energy is passed through an ecosystem
 The arrows show the direction the energy is flowing
 All energy in the food chain comes from the SUN – it is the
sole course of energy of all life
WHAT IS ALWAYS AT THE BOTTOM OF THE
FOOD CHAIN?
Why?
1. Producers are the only organisms that can convert the sun’s
energy into food
2. All living things depend on producers for food
Page 24 in Textbook
FOOD CHAIN TERMS
 A TROPHIC LEVEL tells you the position an organism holds in a
food chain.
- Note: matter and energy are always ‘lost’ as urine, feces,
and heat energy at each trophic level.
 PRIMARY (1°) CONSUMERS feed at the first trophic level
above the producers.
 SECONDARY (2°) CONSUMERS eat primary consumers.
FOOD CHAIN TERMS
 TERITARY (3°) CONSUMERS eat secondary consumers.
 QUATERNARY (4°) CONSUMERS feed at the fourth trophic level
above the producers.
 TOP CARNIVORES are animals that are not hunted for food by
any other animal in the ecosystem.
 1 st LEVEL CARNIVORES are the carnivores that consume
herbivores.
EXAMPLE FOOD CHAIN
4th trophic level
Great Horned Owl
Tertiary (3°) Consumer
(third-order consumer)
(top carnivore)
3rd trophic level
Long-tailed Weasel
Secondary (2°) Consumer
(second-order consumer)
(1st level carnivore)
2nd trophic level
Jackrabbit
1st trophic level
Grass
Primary (1°) Consumer
(first-order consumer)
(herbivore)
Producer
(autotroph)
FOOD WEB
 Food webs are more complex,
showing more interrelationships. They give a more
accurate picture of the
ecosystem.
 They are made of many food
chains and have multiple
energy paths.
AS A CLASS..
Identify:
1. Trophic Levels
2. The primary producer
3. Primary Consumers
4. Secondary Consumers
5. Tertiary Consumers
6. Quaternary Consumers
7. Top Carnivore
FOOD WEB
Answer the questions on the board with your partner
FOOD CHAIN VERSUS FOOD WEB
FOOD CHAIN
- just one path of
energy
FOOD WEB
- many possible energy paths
- contains many food chains
ECOLOGICAL PYRAMIDS
 ECOLOGICAL PYRAMIDS show relationships between trophic
levels. They are another way of showing food chains.
 Pyramids are used to compare the total numbers, biomass, or
energy at each trophic level within the ecosystem.
PYRAMID OF NUMBERS
 Pyramid of Numbers shows the number of species at each
trophic level.
PYRAMIDS OF BIOMASS
 Biomass Pyramid shows the total amount of living tissue
available at each trophic level
PYRAMID OF ENERGY
 Trophic Ef ficiency is the amount of energy transferred from
one trophic level to the next.
 Only 10% of the energy available within one trophic level is
transferred to organisms at the next trophic level.
10 kcal
Largemouth bass
100 kcal
Shiners
1000 kcal
Algae
WHAT IS HAPPENING TO THE ENERGY AS
IT MOVES UP THE FOOD CHAIN?
PRACTICE
 Calculate the trophic ef ficiency of the following energy
pyramids:
ENERGY PYRAMIDS SHOW
 Amount of available energy decreases higher consumers
 It takes a large number of producers to support a small
number of primary consumers
 It takes a large number of primary consumers to support a
small number of secondary consumers
WORKSHEET WITH PARTNER
 Spend the remainder of the class working on the provided
worksheet with a partner. Each student should complete their
own sheet
 Show Miss Mathieu when you are finished!
 Keep your own copy in your binder for a reference on food
chains, food webs, and food pyramids when you are studying
for your unit test