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