(15) Environmental Science

What is an Ecosystem



Ecosystems: What Are They and How Do They Work?

Have You Thanked the Insects Today?

Insects have a bad reputation. We classify many insect species as pests because they compete with us for food, spread human diseases such as malaria, and invade our lawns, gardens, and houses. Some people fear insects and think the only good bug is a dead bug. They fail to recognize the vital roles insects play in helping to sustain life on earth.

Pollination is a natural service that allows plants to reproduce sexually when pollen grains are transferred from one plant to a receptive part of another plant. Many of the earth’s plant species depend on insects to pollinate their flowers. Without pollinating insects, we would have very few flowers, fruits, and vegetables to enjoy. Not all flowering plant species would disappear because some are pollinated by hummingbirds, bats, wind, and flowing water.

Insects that eat other insects-such as the praying mantis - help control the populations of at least half the species of insects we call pests. This free pest control service is an important part of the earth’s natural capital. Some insects also play a key role in loosening and renewing the soil that supports terrestrial plant life. Insects have been around for at least 400 million years-about 4,000 times longer than we have-and are phenomenally successful forms of life. Some reproduce at an astounding rate and can rapidly develop new genetic traits, such as resistance to pesticides. They also have an exceptional ability to evolve into new species when faced with new environmental conditions, and they are very resistant to extinction. This is fortunate because, according to ant specialist and biodiversity expert E.O. Wilson, if all insects disappeared, parts of the life-support systems for us and other species would be greatly disrupted.

The environmental lesson: although insects do not need newcomers such as us, we and most other land organisms need insects. Learning about the roles of insects in nature helps us to understand how they and other organisms interact with one another and with their nonliving physical environment of chemicals and energy in most of the world’s ecosystems. We reach this understanding through ecology, the science that studies such relationships and interactions in nature.

Key Questions and Concepts

3-1 What is ecology?

CONCEPT 3-1 Ecology is a study of how organisms interact with one another and with their physical environment of matter and energy.

3-2 What keeps us and other organisms alive?

CONCEPT 3-2 Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.

3-3 What are the major components of an ecosystem?

CONCEPT 3-3 Some organisms produce the nutrients they need, others get the nutrients they need by consuming other organisms, and some recycle nutrients back to producers by decomposing the wastes and remains of organisms.

3-4 What is biodiversity and why is it important?

CONCEPT 3-4A The biodiversity found in the earth’s genes, species, ecosystems, and ecosystem processes is vital to sustaining life on the earth

ONCEPT 3-4B Soil is an important component of biodiversity that supplies most of the nutrients needed for plant growth and helps purify and store water and control levels of carbon dioxide in the atmosphere.

3-5 What happens to energy in an ecosystem?

CONCEPT 3-5 As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases.

3-6 What happens to matter in an ecosystem?

CONCEPT 3-6 Matter cycles within and among ecosystems and in the biosphere, and human activities are altering these chemical cycles.

3-7 How do scientists study ecosystems?

CONCEPT 3-7 Scientists use field research, laboratory research, and mathematical and other models to learn about ecosystems.

The earth’s thin film of living matter is sustained by grand-scale cycles of chemical elements.

G. Evelyn Hutchinson

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