Transcript Energy_Flow_in_Ecosystems

Energy Flow in
Ecosystems
Environmental Science
Fall 2009
Life Depends on the Sun

Energy enters an ecosystem when a plant uses
sunlight to make sugar (carbohydrates)
 This process is called photosynthesis
6CO2 + 6H2O + energy  C6H12O6 + 6O2
Plants, algae, and some bacteria use sunlight,
carbon dioxide, and water to produce sugar and
oxygen.
Producers

Sunlight is the ultimate source of energy for
most life on earth
 Organisms that convert sunlight into chemical
energy are called producers
Also called autotrophs OR
chemotrophs


Chemotrophs the exception
to the rule – they are found at
the bottom of the ocean where
no sunlight reaches
 Bacteria use hydrogen sulfide to
create energy
 Other organisms feed off the bacteria
Consumers
 Organisms
that consume
other organisms for energy
are consumers (heterotrophs)
 Types of heterotrophs



Herbivores – eat only
producers
Carnivores – eat only other
consumers
Omnivores – eat producers and consumers
More consumers…

Detrivores – also
called scavengers


Eat animal remains
and other dead matter
Decomposers break down organic
matter

Include bacteria and
some fungus
Cellular Respriation

The process in which cells use sugar to create
energy is called cellular respiration
C6H12O6 + 6O2  6CO2 + 6H2O + energy
 Cells use glucose (sugar) and oxygen to
produce carbon dioxide, water, and energy.

Cellular respiration occurs inside the cells of
most organisms
Energy Transfer

Each time one
organism eats
another, energy is
transferred
 Food chains


Show one-way flow of
energy in an
ecosystem
Each step on the food
chain is called a
trophic level
Feeding Relationships
 Food

webs
Includes more
organisms and
multiple food
chains linked
together
Trophic Levels

Visualization of the
loss of energy from
one trophic level to
the next
 Often shown as an
pyramid


Shows relative energy
movement in an
ecosystem
Only 10% of the
energy moves to the
next level
Biomagnification
can lead to biomagnification –
the concentration of toxic substances in
organisms as you move up trophic levels
 Pollution
 Ex.
DDT and birds of prey; mercury in tuna
and sharks