Science1206Final topics and review

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The atmosphere is a mixture of particles and gases which provides air, retains heat that warms the Earth, and has a layer of ozone that protects us

from UV radiation.

The atmosphere is made up of several layers. Two regions: the troposphere and the stratosphere are

relatively closer to the Earth than the others.

•The troposphere extends from the Earth's surface to an altitude as high as seventeen kilometers

above the Earth. In this region the temperature decreases as altitude increases.

•The stratosphere is located above the troposphere to about fifty kilometers above Earth and the temperature increases as altitude increases.

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Sources of Water Pollution

Water pollution is any physical or chemical change in surface or ground water that can harm living things.

Five categories:1)Organic solid waste2) Disease causing organisms3)Inorganic solids and dissolved minerals4)Heat5)Organic chemicals

Water is defined by its intended use. There are three main indicators of water quality:

1)Bacteria count2)Concentration of dissolved oxygen3)Biochemical oxygen demand

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Bacteria

Detection is expensive and difficult. Detecting coliform bacteria is used to see if disease causing bacteria is present. The presence of coliform bacteria indicates that more dangerous bacteria may be present.

Dissolved Oxygen

Different solutions are used to test for oxygen. They change color in the presence of oxygen. Another way is to examine living things in the water. Trout indicate high oxygen levels. Catfish and carp indicate low oxygen levels.

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BOD Biological Oxygen Demand

This is the measure of the amount of dissolved oxygen needed by decomposers(bacteria) to breakdown the organic matter in a sample of water over a 5 day period at 20 degrees C.

It indicates the amount of available organic matter in a water sample. As the number of organisms in an ecosystem increases, so does the BOD.

A productive lake with many living things will have a high BOD. As the number of organisms increases and biological demand increases , more organisms use oxygen from the water. This will cause dissolved oxygen to drop.

(eg. Low value=2 mg/L; high value= 20 mg/L)

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Too many nutrients can create problems for lakes.For example when raw sewage is released into an aquatic

ecosystem.

The greater the amount of decaying matter introduced into the water, the greater will be the population of

decomposing bacteria.Both bacteria and fish use oxygen, and fish will die if

oxygen levels drop too low.

Dead fish create detritus which further promotes bacteria growth. To prevent damage to ecosystems cities

install water treatment plants.

Sewage, Decomposers and Oxygen Levels

Aquatic eutrophication One of the factors that determines how many of these

microscopic organisms live in the water is the availability of nutrients.

The nutrients that have the most profound effect on the number of microorganisms found in the water are nitrates and phosphates. Low levels of nitrates and phosphates reduce the number of micro-organisms. The water appears clear and sunlight can penetrate deeper supporting the production of oxygen by photosynthetic organisms.

Under these conditions, the pond or lake can support large populations of fish and other organisms that are adapted to relatively high levels of oxygen. Such a lake in which oxygen levels are relatively high is known as an oligotrophic lake.

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Aquatic eutrophication

• Bodies of water enriched by nitrates and phosphates mainly from agricultural lands and from untreated human or animal sewage causes the number of micro-organisms to increase to the point that the water actually appears turbid (cloudy). As a result of the bacteria, less light is able to penetrate the water and oxygen concentrations tend to be reduced. Such a lake is said to be eutrophic.

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Go to Work

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• Read 4.2 "Sources of Water Pollution" on pages 132 - 134.

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Describe what is meant by short term stress and long term change

Identify factors that cause extinction of animals including: influence of humans, climate change, and pressure of competition

Compare a natural and an artificial ecosystem in terms of the influence of different abiotic factors on the organisms that live there

Describe how acid deposition affects a forest ecosystem

Describe how the introduction of an exotic species (zebra mussel) has affected life in the great lakes

Short Term Stress and Long Term Stress

• The way that a population responds to short term stress and long term change depends on the ability of the

organisms within the population to continue to meet their biological needs for appropriate range of climatic

conditions (temperature, light, moisture), food, water, shelter, space, and opportunity for reproduction.

• Most organisms are capable of withstanding a loss of one or more of these factors for a short period of time, but will die if one or more of these biological needs is not met for a long period of time. Some populations may become extinct

as a result of long term change.

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Examples of short term stress include seasonal peaks in temperature, sudden changes in water supply, or sudden but

limited human impact.

Climate change (global warming), infestation by foreign plants and animals (exotic species), and

permanent human influence (habitat destruction, acid deposition, etc.) are examples

of long term change.

Pine Marten

Keystone Species• A keystone species is one considered so important to

the stability of the ecosystem, that if there was a decline in that species, the community would not be able to maintain its stability and may even collapse.• Nearly any arctic organism could represent this

• Killer Whale Prairie dog European Beaver Flying Fox Grizzly Bear

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