Introduction to

ENERGY FLOW

FOOD WEBS

AND

PYRAMIDS

Food Chains & Food Webs

Most organisms feed on more than

one trophic level and feed on

several different species at each

trophic level.

Food Chains & Food Webs

A food web is a series of interconnected food chains.

#1

Biomagnification

Increase in concentration of a

substance throughout the food

chain

http://www.youtube.com/watch?v=E

5P-UoKLxlA

sun eclipse with palm

The ultimate energy source is the

SUN

Ecological Pyramids

Instead of

representing

trophic levels in

a food chain, an

ecological

pyramid can be

used.

Ecological Pyramids

This

pyramid

represents

a food

chain.

#2

Ecological Pyramids

This pyramid would represent a food web if different organisms were present together at each level .

For example, a frog and a mouse on level 3 and/or a grasshopper and butterfly on level 2.

Types of pyramids

3 Types of ecological pyramids

–Energy

–Numbers

–Biomass

Pyramid of Energy

The big numbers represent the trophic levels.

kcal represents

the energy content at that level.

#3-4

Pyramid of Energy

As you go up the pyramid, the energy level

decreases.

Only about 10% of the

energy from the

previous level is

available.

This pyramid is called

an energy pyramid

because it shows the

amount of energy at

each trophic level.#5-7

Pyramid of Numbers

The numbers

pyramid

represents the

total number

of individuals

counted at

each level.

#8

Pyramid of Numbers

To get a number

total for a

population of

organisms, you

have to count

the organisms in

a specific area,

such as an acre

and then

estimate.

#9

Pyramid of Biomass

A biomass pyramid represents an

estimate of the mass of the

population.

To get this

information, you

calculate the mass

of a sample of

organisms and

then estimate.

#10

Ecological Pyramids

A pyramid is often used to represent

feeding relationships because

energy, biomass and the number of

organisms generally decrease as you

move up the food chain.

Ecological Pyramids

This pyramid is different because it shows the producers as being very small.

Something to think about (but not answer yet): How can the producer level be so small and support the trophic levels above it?

Pyramids of Aquatic

Ecosystems

Numbers

Biomass

Energy

Pyramids of Temperate

Forests

Numbers

Biomass

Energy