The start of the problem • Many chemicals we use in our daily lives are toxic. Toxic chemicals include: • pesticides, • engine products and • many household cleaners. Most toxins are made by humans; they do not occur naturally.
Some of these toxins are persistent. • Persistent toxins can cause the following problems: • Reproductive failure • Birth defects • Immune system disorders (cancers and weakness to disease) • Behaviour and learning disorders • Death • Persistent toxins are also known as Persistent Organic Pollutants (POPs).
Waterways get polluted by: • Runoff from pesticides • Runoff from fertilisers • Stock effluent seepage and dispersal • Sedimentation from land clearance/erosion
Traveling through food chains • We (humans) may use toxins on land, but they can travel through the soil in groundwater into waterways and into the ocean. • All persistent toxins eventually end up in ocean food chains.
Bioaccumulation vs Biomagnification • Bioaccumulation refers to the accumulation of a toxic chemical in the tissue of a particular organism. • Biomagnification refers to the increased concentration of a toxic chemical the higher an animal is on the food chain.
The Effect of the Pollutant • Different organisms show varying degrees ofsensitivity to toxins. Even within a species,sensitivity to a particular toxin may depend onage, sex, food availability, reproductive condition • with DDT, the egg shells of large birds were so weak that they would be crushed by the weight of the adult birds.
A little goes along Way From the article: Blooms and Gloom Dinoflagellates are microscopic and some species can produce toxins – which can harm an organism.
Question 2 • ??????
Answer 2 • Biomagnification refers to the increased concentration of a toxic chemical the higher an animal is on the food chain. • Own words????
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Answer 3: Western Port Bay • a) Food chains: Detriustube worm squirter worm black bream pelican • b) DDT increases from 1.4 to 22.8 in this food chain Tern, Pelican, Cormorant are all
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Carnivores as they eat meat • The Black swan is the only bird that is a herbivore Answer 4
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Answer 5a:DDT levels in various organisms • a) Tern DDT level is less than the Pelican or the cormorant because: Tern is a 3rd order consumer Pelican is a 4th order consumer Cormorant can be a 4th order consumer
Answer 5b:DDT levels in the Black Swan • Black Swan feeds on eel grass and not detritus, therefore the DDT levels are lower in the swan compared to other birds
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Answer 6:DDT in detritus is very high • decomposing organic matter is found in the detritus – so any organism that had a high DDT content in it and dies will leave this DDT in the detritus
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Answer 7:Which fish would you buy? • Black Bream = 2.1 • Yellow-eye mullet =1.4 • King George whiting = 1.2 • Reason???
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Answer 8:How does DDT find its way into waterways??? • Runoff from pesticides • Runoff from fertilisers • Stock effluent seepage and dispersal • Sedimentation from land clearance/erosion
Question 9 • ????
Answer 9:Non-degradable substances • Summarize how they accumulate • What we want instead is: ✔
Biochallenge answers page 468 Answer a • Birds of prey are further up the food chain than the seed-eating birds and would be more affected by the accumulation of DDT
Answer b The average thickness of the shells over time has been reduced. The majority of the dots are 1.4 in mid 1970, compared to 2.0 in 1890
Answer c A range of thickness observed in egg shells in the same year could indicate: • Eggs were collected from different regions • Some birds may not have consumed as much DDT as others through their feeding
Answer d Based on the graph the DDT was most likely used extensively in Australia just before 1950 Evidence for this can be seen in the increase in dots at index 1.2 and 1.4
The idea is: DDT causes thinning of the shells of eggs Answer e Observation 1 supports the idea that DDT causes thinning of the eggshells Observation 2 neither supports or disproves this idea Observation 3 neither supports or disproves this idea
Answer f: DDT levels in breast milk from urban and rural areas in 1971 & 1979 • In 1971 Urban and rural differences existed because the DDT was entering the food chain via agricultural use – treatment for termites in rural areas • The change from 1971-1979 was that urban numbers decreased from 2300-1200, and rural numbers decreased from 17,000 to 1200 – due to the restrictions the government put on the way to treat termites