Steve Geraghty, age 12, of Bowling Green, Ohio,forhis question:

WHAT IS ACID RAIN?

Acid rain is caused by the ejection of sulfur dioxide and nitrous oxides into the atmosphere from power plants and motorvehicles. These chemicals interact with sunlight, moisture and oxidants to produce sulfuric and nitric acids, which are carried with the atmospheric circulation and come to earth in rainfall and snowfall.

Some precipitation in northern North America and Europe is equal to vinegar. It corrodes metals, weathers stone buildings and monuments, injures vegetation and acidifies lakes, streams and soils, especially in the poorly buffered, glaciated granite regions of northeastern North America and northern Europe. Lake acidity in those areas has already killed some fish populations.

Acid rain is also now a problem in the southeastern United States and in central North Africa. Acid rain can destroy aquatic life and slow forest growth. Thus. it is a major global environmental problem.

James Holmes, age 14, Casper, Wyo., for his question:

CAN YOU EXPLAIN ECOLOGY?

Ecology is the study of the relationship of plants and animals to their physical and biological environments. It is a branch of biology. Scientists who specialize in studying these relationships are called ecologists

Physical environment includes light and heat or solar radiation,  moisture, wind, oxygen, carbon dioxide nutrients in soil, water and atmosphere. The biological environment includes organisms of the same kind as well as other plants and animals.

To study organisms in their environment, ecologists draw upon such fields as chemistry, geology and soil analysis. To study the relationships between organisms involves such diverse sciences as animal behavior, taxonomy, physiology and mathematics.

The word "ecology" has become a common but often misused word because of an increased public awareness of environmental problems. It is sometimes confused with environmental programs and environmental science. Although the field is a distinct scientific discipline, ecology does indeed contribute to the study and understanding of environmental problems.

The term "ecology" was introduced back in 1869 by a German biologist named Ernst Heinrich. It is derived from the Greek word "oikos," meaning "household," and sharing the same root word as "economics." Thus the term implies the study of the economy of nature.

Modern ecology for the most part, started with Charles Darwin. Darwin stressed in developing his theory the adaptation of organisms to their environments through natural selection.

Also making important contributions were plant geographers who were deeply interested in the "how" and "why" of vegetational distribution around the world.

Ecologists study the activities and changes in the natural world. They study how all living things in an area, the biological or biotic environment, are related to each other and to the physical environment of earth, water, air and energy.

A biological community and its physical environment form what ecologists call an ecosystem. This is a term that was coined in 1935 by a British plant ecologist Tiamed Sir Arthur Tansley to stress the concept of each locale or habitat as an integrated whole.

A system is a collection of interdependent parts that function as a unit and involve inputs and outputs. The major parts of an ecosystem are the producers (green plants), the consumers (herbivores and carnivores), the decomposers (fungi and bacteria) and the nonliving (abiotic) component, consisting of dead organic matter and nutrients in the soil and water.

Inputs into the ecosystem are solar energy. water, oxygen and carbon dioxide, nitrogen and other elements and compounds.

Outputs from the ecosystem include heat of respiration, water, oxygen, carbon dioxide and nutrient losses. The major driving force is solar energy.

For an ecosystem to continue functioning, nutrient outputs must balance inputs. If inputs greatly exceed outputs, the system's cycle becomes stressed or overloaded, resulting in pollution. Pollution can be considered an input of nutrients exceeding the capability of the ecosystem to process them.