Transcript Food Webs and Energy Transfer

Matter Cycles, Energy Flows
Producers/Autotrophs
Sunlight is the main energy source for life
 Photosynthesis is the conversion of inorganic
molecules to sugars by photoautotrophes

Photosynthesis
inorganic
radiant
+ energy
matter
organic (C) matter
extra
(chemical energy) + atoms
[ Chemoautotrophes
Some autotrophes rely on energy stored in chemical
bonds of inorganic compounds (H2S) found at
hydrothermal vents ]
Consumers /Heterotrophs
Rely on other organisms for food (nutrients, fuel)
Primary consumers are herbivores (plant eaters)
producer
energy &
matter
transferred
primary
consumer
Respiration
Secondary Consumers
Carnivores that eat herbivores
producer
energy &
matter
transferred
primary
consumer
energy &
matter
transferred
secondary
consumer
Tertiary consumers
Carnivores or omnivores that eat carnivores/omnivores
aka top
consumers
Producers
etc
energy &
matter
transferred
Detritivores
consumers that derive
energy from organic
waste and dead
organisms
Bacteria, insects ,fungi
aka decomposers
Food Web contains many food chains
Arrows
indicate
energy
transfer
Pyramid Power
Shape reflects
trophic (feeding)
levels
Greek: trophos =
nutrition
Pyramid shape reflects energy use & transfer
Only 10% is
transferred on
average
Most energy is
transformed
(lost) into heat
Pyramid shape reflects number of organisms
Many producers
needed to
support a smaller
number of
consumers
Pyramid shape reflects relative biomass
Large base
supports smaller
(less productive)
trophic levels
Biomagnification/Bioaccumulation

Chemicals ingested that
cannot be broken down
or easily excreted

These accumulate in
tissues

The more one eats, the
more toxin that
accumulates
Organisms higher in the web have more opportunities to
ingest the toxin, increasing concentration in their tissues
10,000x
1,000x
100x
10x
1x
It’s exponential
13.8ppm
2.07ppm
0.23ppm
0.04ppm
The pyramid
is inverted
Greatest quantity of
toxin per individual is in
those top consumers
Mercury concentrates in fish
Brain damage, death
Limit your tuna intake:
Albacore 1x/2weeks
Chunk light 1x/5 days
Source: EPA/FDA
For a 100# person
DDT
Weakens bird egg shells
PCB’s from electrical, plastics industries
Linked to cancer
Also immune,
reproductive,
neurologic,
endocrine
disorders