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 CO 2 + light Respiration C 6 H 12 O 6 + O 2  CO 2 + H 2 O carbon dioxide water glucose oxygen glucose oxygen carbon dioxide water H 2 O  C 6 H 12 O 6 + O2O2

Only plants do photosynthesis

All cells must do respiration

Decomposers break down dead plants & animals, releasing CO 2 into the air Fungi decomposing a log. Bacteria decomposing a tomato.

Humans burn fossil fuels and release ever more CO 2 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 unit 1 snake eats 20 frogs each with 2500 units 1 frog eats 25 cricket each with 100 units 1 cricket eats 100 blades of grass each with 1 unit DDT some blades of grass gets 1 unit DDT when we spray an area NO HARM  units in hawk  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