BIOLOGY CHAPTER 30
Humans and the Environment
30.1 The Pesticide Dilemma
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Advances in agriculture and industry have
prolonged and enriched the lives of humans.
The by-products produced are undesirable.
Pesticides that protect crops from insects also affect
the health of birds, fish, and humans.
Automobile exhaust, factory emissions, and
pesticides are examples of pollution – a
contamination of air, water, or soil by materials
released into the environment.
What is a pesticide?
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A chemical poison used to kill an unwanted
organism.
Examples: termites, moths, aphids, weeds, etc.
Weeds alone cause 10% loss of agricultural crops
per year.
We’ve learned in the last few chapters how to keep
populations in check.
When we plant a single field of one species, pest
populations can grow so large as to affect the
harvest.
Humans probably transferred the pests
to other parts of the world.
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Fruit flies were brought in from fruit smuggled from
Hawaii.
The flies have no natural predators here.
Populations grow unchecked.
Japanese beetles and gypsy moths are other
examples of transplanted pests.
Benefits of pesticides
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Have enabled us to replace natural ecosystems with
farmland, golf courses, lawns, and gardens.
Have enabled farmers to produce larger quantities
of food.
Look at corn harvest: Good year maybe average
220 bushels.
Average in 1950: 47 bushels per acre.
Problems with pesticides
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Only 10% lands on pests – other 90% hits harmless
organisms, predators of the pests, and gets in the
soil and water.
The pests that survive become resistant to the
pesticides.
These reproduce and produce a resistant population
over time.
Entire ecosystems can be affected by their use.
DDT
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1939 it was found to be extremely effective in
controlling insect pests.
Side-effects were not immediately known.
Banned in the U.S. now, but used in other parts of
the world.
Biological resistance built up in the organisms we
tried to kill.
DDT
Biological Magnification
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DDT remains toxic long after release.
Its nonbiodegradeable.
DDT biological magnification close to
home:
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Can be seen in red tail hawk population.
In small doses, it is not fatal to small birds and other
animals.
But it is still present in the tissues.
Concentration gets higher as we move up the food
chain.
When I was growing up, there were never any red
tail hawks in Iowa.
Now you can’t drive a mile without seeing one.
Alternatives to pesticides
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Cultural controls – devising methods that discourage
pest growth in the first place.
Biological control – introducing predators from
another area to keep pest population in check.
Autocidal control – sterilizing male species and
introducing them into an area.
Integrated pest management – system using all
three of these controls to check populations.
30.2 Pollution of Air and Water
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One of the chief causes of air pollution is burning of
fossil fuels.
By-products include carbon monoxide, carbon
dioxide, sulfur dioxide, nitrogen oxides, lead
compounds, and hydrocarbons.
All of these are considered pollutants.
Air Pollution
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Carbon monoxide – CO bonds with hemoglobin in
the blood. It takes up space reserved for oxygen.
Nitrogen oxides – can damage lungs, cause eyes to
tear, and contributes to ozone.
Ozone layer up in the atmosphere is actually a
good thing. Blocks out harmful UV rays.
Chloroflourocarbons (CFC’s) can damage the ozone
layer.
Acid Rain
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Rainfall with a pH of 5.5 and below is considered
acid rain.
Can wash nutrients out of the soil.
Can cause lakes to become dead zones.
Can alter the pH of the soil over time.
Global Warming
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Book talks about global warming next, but we will
study this on our own after this chapter.
30.3 Conservation of Resources
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Genetic Engineering – 200 bushels of beans/ acre
Focusing on renewable resources more.
Minimizing erosion.
Using alternative fuels (nuclear, solar, and
hydroelectric energy)
Conserving wildlife and habitat.