PESTS AND PESTICIDES bioaccumulation

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PESTS AND PESTICIDESbioaccumulation

• Grade 9 Science

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PESTS AND PESTICIDES

• Pests are organisms that compete with or damage
  crop species. Examples include weeds,
  caterpillars, and mice.
• To maximize the growth of a crop, farmers try
  toeliminate pests.
• In nature, there are no such things as pests. All
  organisms are producers or consumers within food
  webs.

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• By controlling pests, farmers grow crops in an
  environment with hardly any consumers or
  competitors.
• When farmers plant monocultures, they create
  ideal environments for pests. If not controlled,
  pest populations could increase enough to
  devastate the entire crop.

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• Pesticides are poisons that kill pests.
• Types of pesticide include herbicides,
  insecticides, and rodenticides.

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CHARACTERISTICS OF PESTICIDES

• Long-lived pesticides persist in the environment
  for many years.
• Short-lived pesticides degrade in a matter of
  days.
• Broad-spectrum pesticides are toxic to a wide
  rangeof pest species.
• Narrow-spectrum pesticides are toxic to a limited
  number of species.
• Pesticides work by causing biological or physical
  harm to organisms.

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ISSUES WITH PESTICIDES

• Pesticide use has many benefits, but also has
  significant environmental costs.
• Sprayed pesticides that land on soil or are
  carried away by the air may become sources of
  pollution.
• Pesticides often kill species they were not
  intended to kill. For example, a broad-spectrum
  pesticide might kill the predatory insects that
  feed on pests.

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• Improper use of pesticides, such as spraying at
  the wrong time of year, can also kill non-target
  species.
• The consequences of non-target killing can be
  surprising and serious, such as the chain of
  events that took place on Borneo after spraying
  DDT to kill mosquitoes.

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What is ddt?

• colorless contact insecticide, toxic to humans
  and animals when swallowed or absorbed through
  the skin

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Where is borneo?

• Borneo is the third biggest island in the world
• It comprises three countries Malaysia as well
  as Brunei on the north side and Indonesia on the
  south
• The Dayak tribe are the indigenous people that
  live there

http//www.youtube.com/watch?vdYXCjENbqSs
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Borneo and ddt

• In the early 1950s, there was an outbreak of a
  serious disease called malaria amongst the Dayak
  people in Borneo. The World Health Organization
  tried to solve the problem. They sprayed large
  amounts of a chemical called DDT to kill the
  mosquitoes that carried the malaria. The
  mosquitoes died and there was less malaria. That
  was good. However, there were side effects. One
  of the first effects was that the roofs of
  people's houses began to fall down on their
  heads. It turned out that the DDT was also
  killing a parasitic wasp that ate thatch-eating
  caterpillars. Without the wasps to eat them,
  there were more and more thatch-eating
  caterpillars. Worse than that, the insects that
  died from being poisoned by DDT were eaten by
  gecko lizards, which were then eaten by cats. The
  cats started to die, the rats flourished, and the
  people were threatened by outbreaks of two new
  serious diseases carried by the rats, the plague
  and typhus. To cope with these problems which it
  had itself created, the World Health Organization
  had to parachute live cats into Borneo.

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DDT and rachel carson

• http//www.youtube.com/watch?vuARFfWFcV5Afeature
  related

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ISSUES WITH PESTICIDES - BIOACCUMULATION

• Some pesticides do not break down in the body. If
  an individual eats food contaminated with the
  pesticide, it accumulates in the body.
• The pesticide may continue to accumulate as the
  organism eats more contaminated food. This
  process is calledbioaccumulation.

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DDT BIOACCUMULATES UP THE FOOD CHAIN
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BIOAMPLIFICATION

• Pesticides that bioaccumulate are soluble in fats
  and oils, not water.
• Pesticides stored in the fat of organisms at one
  trophic level are passed on to consumers at the
  next trophic level.
• The higher up the food chain, the more
  concentrated the pesticides become. This process
  is called bioamplification.
• Arctic ecosystems are particularly vulnerable to
  bioamplification. Many long-lived top consumers
  live in the Arctic, such as whales, polar bears,
  and walrus. Inuit living in these environments
  rely on these species for food.

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BIOAMPLIFICATION OF MERCURY
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Pesticide Resistance

• Pest species may become resistant to a pesticide
  if it is used for a long time.
• When a pest species develops resistance, farmers
  need to apply a greater concentration of
  pesticide, or switch to a different pesticide.
• Pesticide resistance is a serious concern
  worldwide.

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