Carbon and Chemicals in Food Chains Page 22. . THE CARBON CYCLE Carbon is the key element of life...
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Transcript of Carbon and Chemicals in Food Chains Page 22. . THE CARBON CYCLE Carbon is the key element of life...
Carbon and Chemicals in Food Chains
Page 22
. THE CARBON CYCLE
Carbon is the key element of life
Carbon does not decrease as it moves up a food chain, rather it is changed and
recycled
CARBON CYCLE: Two key steps Photosynthesis
CO2 +light
Respiration
C6H12O6 + O2 CO2 + H2O
carbon dioxide water glucose oxygen
glucose oxygen carbon dioxide water
H2O C6H12O6 + O2
Only plants do photosynthesis
All cells must do respiration
Decomposers break down dead plants & animals, releasing CO2 into the air
Fungi decomposing a log. Bacteria decomposing a tomato.
Humans burn fossil fuels and release ever more CO2 into the air
Car exhaust Industrial fumes
Other cycles:
There is a nitrogen cycle that includes: (tomorrow)proteins, muscles, wastes and bacteria decomposers
bones & teeth, rocks and weathering
There is a slow phosphorus cycle that includes: (tomorrow)
BIOAMPLIFICATION This refers to an increase in levels of a
chemical as you move up a food chain
Fish provides a heart-healthy source of protein and contains a host of nutrients including omega-3 fatty acids and vitamin B12.
Mercury exists in our waters and subsequently in fish eat.
The concentration of mercury in local-waters varies, and therefore, the content in any given fish.
Due to bioamplification, fish at the top of the predator chain are far more likely to contain high amounts of mercury than smaller fish.
BIOAMPLIFICATION The chemical must be fat soluble,
otherwise it is simply urinated out
If a carnivore eats an animal, it accumulates all of the chemical in that animal’s fat
and retains it for its whole life
Animals high in the food chain may accumulate lots of chemical
BIOAMPLIFICATION: Example The chemical DDT was sprayed to kill
mosquitoes
It did kill the mosquitoes, but some chemical ended up on leaves & grass
That chemical could enter food chains such as the one on the next slide
grass
cricket
frog
snake
hawk
1 hawk eats 10 snakes each with 50000 unit
• 1 snake eats 20 frogseach with 2500
units• 1 frog eats 25 cricket
each with 100 units
• 1 cricket eats 100 blades of grasseach with 1 unit DDT
• some blades of grass gets 1 unit DDT when we spray an area
NO HARM
NO HARM
NO HARM
NO HARM
500000 units in hawk
50000 units in snake
2500 units in frog
100 units in cricket
Effect of DDT If DDT at 500,000 units does NOT harm hawks, why are we concerned?
• DDT above 100,000 units makes egg shells thinner
• When the adult sits on these eggs, they break
• As a result, hawk and eagle populations dropped greatly in the 50’s, 60’s and 70’s
when DDT was used
Banning DDT Canada, U.S. and Europe have banned
DDT and bird populations have recovered
but South America and Africa still use DDT because it is cheap and effective at killing mosquitoes [which carry disease that kills millions of people each year]
Other chemicals Other fat soluble chemicals may
cause sperm problem in mammals
• New pesticides are not fat soluble and so cause fewer problems.
Some chemicals cause baby whales to refuse mother’s milk
In India, vultures clean-up the carcasses of the dead cows
But, 97% of all Indian vultures died between 2002 and 2006
The question was, what can be killing the vultures?
The first thing they noticed was that the vultures were sick for only a short time before death
Autopsies showed kidney failure.
Diclofenac – is an anti-inflammatory drug used on cattle
They then looked at what vultures ate, and concluded it was a cattle problem.
Originally they thought it was a virus, but it did not spread when healthy birds were put with sick birds.
Researchers were able to show that Diclofenac shuts down the vulture’s kidneys
and in late 2006 they banned the drug