Transcript Food Chains and Food Webs

Food Chains and Food
Webs
Structure and Function
Diagrams used to show how energy
moves through an ecosystem.
Food Chain



A food chain is a diagram that shows
one particular example of energy
flow through an ecosystem.
Includes one organism per trophic
level.
Trophic level - place in the food
chain based on separation from the
sun
Food Web


Shows how energy flows through the
community.
Show more than one organism per
trophic level
Laws of Thermodynamics


1st Law of Thermodynamics- Energy
can never be created or destroyed in
a chemical reaction. It can only be
transferred from one form to
another.
2nd Law of Thermodynamics- Any
time energy is transformed that
process is not 100% efficient. Some
energy is converted to an unusable
form.
Implications for the Laws of
Thermodynamics

1st Law of Thermodynamics• Plants are able to convert light energy
to chemical energy in glucose and other
organic compounds
• Organisms that eat plant can covert
chemical energy stored in plant to forms
they can used to do work.

2nd Law of Thermodynamics
• Not all solar energy an autotroph
converts is usable to heterotrophs.
Some of that energy is used by the
autotroph.
• Some energy from the heterotroph is
also required to digest and store energy
they consumed.
• Therefore, there must be more energy
stored in the 1st trophic level than the
2nd, and more energy in the 2nd trophic
level than the 3rd.
Rule of 10%


In general 10% of the energy and
biomass stored in one trophic level
can be passed on to the next trophic
level.
This can diagramed using energy and
biomass pyramids.
Energy
Pyramid
Biomass Pyramids
A question


Given This Why are Carnivores Good
Predictors of Ecosystem Health?
If there is any trouble in a food chain
it will effect the top trophic level
Biodiversity & Stability

What’s biodiversity?

The number of different kinds of species
living in an area.

How does ecosystem biodiversity affect
ecosystem stability?

the more biodiverse the ecosystem the
more options. The more options, the
more stable
Introduced Species and Changing
Food Webs


Sometimes nonnative species are
introduced by humans into an
ecosystem. When this happens, they
may disrupt the cycle of energy flow.
How?
Adding a new member to a food web
will reduce resources from others
Rabbits in Austrailia
Rabbits in Australia

Rabbits are not native to Australia.

24 rabbits were introduced in 1859.

They reproduced, well like rabbits,
and the population rose quickly to
over 2 billion by 1952.
Introduced Species



Why do you think the population increased
so quickly and so much?
What do you think happened to the native
plant population?
What do you think happened to the
populations of animals that the competed
for resources with the rabbits?