Transcript Food Webs and Pyramids

Food Webs and Pyramids
Nutrients and
energy flow
through
ecosystems in
food chains
and food
webs.
Food Chains
A food chain is the flow of energy
from one organism to another.
The arrows in a food chain
represent the energy flow!
 Here is an example……
Trophic Levels
Contains all organisms in a
feeding level that are the same
number of steps away from the
sun.
Moving up each trophic level,
there is a 90% loss of heat.
That means that
only 10% of
energy is passed
along from one
level to another.
Because of the
huge loss of
energy, there is
usually no more
that 4 or 5 trophic
levels.
VOCABULARY
1. Autotroph (producer) –
Organisms that can make its
own food.
2. Heterotroph (consumer) –
Organisms that relies on other
organisms for food
3. Primary consumer – the
first consumer that eats the
producer
4. Herbivore – organisms
that eat only PLANTS
5.Secondary consumer – second
level consumer that eats a first
level consumer
6.Tertiary consumer – third level
consumer
7. Carnivore – organisms that
eat only MEAT
8. Omnivore – Organisms
that eat both PLANTS and
ANIMALS
 9.
Decomposer (saprophyte) –
type of bacteria or fungus that
breaks down dead organisms
and wastes
10.Detritivore (detritus feeder)
– organisms that shred and
consume already dead
organisms and matter
(other than bacteria and
fungi).
FOOD WEBS
Interconnecting food chains
Gives us a better picture of the
ecosystem
Keystone Species
A species that has a strong or
wide-reaching impact on a
community is called a keystone
species.
If the keystone species is
removed, the community will
collapse and alter a large portion
of the food web.
Ecological Pyrmaids
Graphic way to represent the
relationship energy values in
each tropic level.
The bases of these pyramids
represent the producers.
Higher trophic levels are
layered on top of one another.
The source of energy for these
pyramids is the sun.
T YPES OF PYRAMIDS
Pyramid of Energy
Pyramid of Numbers
Pyramid of Biomass
PYRAMID OF ENERGY
Illustrates the energy content of
biomass of each tropic level.
Energy expressed in
kilocalories/square meters.
Larger at the bottom and gets
progressively smaller.
Shows that most of the energy
dissipates at the lower levels
The energy lost in each
successive trophic level is heat
that enters the environment.
Energy pyramids explain why
there are few trophic levels.
No biological process is 100%
efficient. There will be unusable
energy.
PYRAMID OF BIOMASS
Illustrates the total biomass at
each trophic level.
Biomass is a quantitative estimate
of the total mass or amount of
living material.
Biomass units vary. It can be
represented by total volume or
live weight.
Assumption – There is on the
average a 90% reduction of
biomass for each trophic level.
Biomass is calculated by finding
the average weight of an
organism of each species at that
trophic level and then
multiplying by the estimated
number of organisms in each
population.
Although carnivores do not eat
a lot of producers, it takes a lot
of producers to support them.
PYRAMID OF NUMBERS
This pyramid is based on the
number of organisms at each
level.
Not as useful as the other
pyramids because it provides no
information about energy levels
or biomass.
Inverted pyramid of numbers –
higher trophic level organisms
have more than lower trophic
levels.
INVERTED PYRAMID OF NUMBERS
Blue birds