Science 9
Unit 3: Environmental Chemistry
Name: Danielle Murray
Topic 2: Pesticides
Pesticide use is now common practice worldwide. Herbicides control weeds,
insecticides control insects and fungicides control diseased crops. The use of
chemicals, such as DDT, was originally thought to be directed only at the insects
it was intended for. Unintentional harmful effects to other species resulted in a
closer look.
Issues Associated With the Use of DDT
The invention of DDT by Swiss chemist Paul Müller was seen originally as a
breakthrough in medicine. Typhus -transmitted by lice- which wiped out
Napoleon’s army in the 1800s, was rampant during World War II among the
Allied troops. DDT wiped it out. It proved to be so effective that Müller was
awarded the Nobel Prize in Medicine for his discovery. During the 1950s it was
used to try to control an outbreak of malaria.
The DDT Story
When DDT gets into the food chain bioaccumulation can have devastating
effects. As you move up the food chain the concentrations of DDT are higher.
What’s Bugging You?
The use of DDT was recognized as having potentially harmful effects. Banning its
use would also negate the positive effects it was having in controlling malaria (In
Zanzibar alone – the incidence of malaria dropped from 70% to 5% over a 6 year
span). When a restriction on the use of DDT was implemented in 1984, the
incidence of malaria returned to the 50-60 % level. Nothing else proved to be as
effective in controlling the insects that carried malaria. Should DDT be banned
completely?
Producing safe and effective insecticides, as alternatives to DDT is difficult due to
cost, effectiveness and the problem of resistance.
Where to Now?
No matter how it is developed, a pesticide (insecticide) is used to control pests.
The potential these chemicals have to harm non-target species has caused
concern and restraint on the widespread and uncontrolled use of pesticides in the
environment. Research and development into newer and safer pesticides has
resulted in these pesticides breaking down faster in the environment after they
have been applied. It is now widely recognized that natural processes and cycles
can minimize the effects of these pesticides, but it still remains a hotly debated
issue. In the future researchers must determine what effects combinations of
these pesticides will have on the environment and ultimately us.
Topic 2: Pesticides Assignment
1. Complete Topic 2 Review questions #1-6 on p. 196 of your textbook.
2. Investigation 3-B (p.189-191) Complete questions 1-8 & 11
Topic 2 Review questions #1-6 pg. 196:
1. What is a pest? What are pesticides?
A pest is weeds, Insects and Fungi. Pesticides are Herbicides (a chemical
used to control weeds), Insecticides (a chemical used to control insects) and
Fungicides (a chemical used to control moulds and fungi).
2. This event could occur in 1948 because people didn’t see anything bad
about using DDT. This event could not occur in 1978 because people
knew and found out what DDT was doing to the environment and people.
3. The difference between toxic and poisonous is that a toxic affects you
over time and poisonous affects you immediately.
4. Organic farming is farming that doesn’t use pesticides on the produce.
Yes, organic farming is better than conventional farming because organic
farming doesn’t use pesticides whereas, conventional farming uses
pesticides on produce.
5.
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use lady bugs to reduce pesticides in your home or yard
Don’t buy pesticides
Try to find pesticides that aren’t as harmful
6. Pesticides are harmful t birds at or near the top of the food chain because
the pesticides can travel to the water or the animal or insect (lunch) that
the bird is going to get can be affected by the pesticides and affect the
bird.
Investigation 3-B (pg.189-191) Complete questions 1-8 & 11:
1. DDT enters a food web by being used on crops to control damage caused
by insect pests, the pesticides spread throughout the environment. The
DDT was also sprayed in the areas where the animals were and caused
them to die.
2. The dolphins contain the most DDT.
3. The dolphins are at a higher trophic level
4. The relationship between the trophic level and the concentration of DDT in
the organisms body is that the higher up the animal is in the food chain the
more DDT it has in its body.
5. The fish is 43 times greater concentration of DDT than seawater. It is 5,
200 times greater in the dolphins than in the seawater.
6. Animals at the top of the food chain are particularly at risk from poisons in
the environment because the DDT is being used on land and it only floats
on top of the water.
7. An animal living hundreds of Kilometers away from an area sprayed with
DDT might get DDT in its body by breathing in the air that DDT might be
floating in or by eating an animal or insect that was exposed to DDT and
eating it.
8. These characteristics are undesirable in pesticides because then people
would want to buy the product that they used to buy from the farmer and
there would be less food to go around. The characteristics you would want
in a pesticide to make it less harmful to non-pest organisms would be that
the pesticide would have no harmful effect on killing the non-pest
organism.
11. a) The general differences between pesticide levels in birds’ eggs nesting
in the Bay of Fundy and pesticide levels in the Atlantic Ocean is that there is
more DDT in the Bay of Fundy than in the Atlantic Ocean.
b) The changes in pesticide levels in 1972 to 1984 is that the pesticide level
decreased. The restriction of DDT after 1969 may be the account for the
pesticide level decrease.
c) The differences in pesticide levels found in different species is that for
Leach’s storm- petrel (feeds on small organisms near the surface of the water)
the DDT was high because the small organisms were more affected by the DDT
and were closer. The Atlantic puffin (feed on smaller fish) DDT pesticide level
was small because the organisms the Atlantic puffin ate weren’t that affected by
DDT and were not as close to the dry land. The double- crested cormorant
(feeds on larger fish) is higher in DDT because the organisms the double-crested
cormorant ate were more affect with DDT and then the double- crested
cormorant ate it.
Vocabulary Words:
Pesticides- a chemical used to control “pests”
Herbicides- a chemical used to control weeds
Insecticides- a chemical used to control insects
Fungicides- a chemical used to control moulds and fungi
DDT- Dichloro Diphenyl Trichloro ethane- poison against several insects, also
affects human health.
Biomagnification – The process whereby chemicals accumulate in the tissues of
organisms along the food chain.
Toxic- Happens over a long time to cause effects
Poisonous- Happens immediately causing effects to you