Chapter 3
Ecosystems: What Are They and How Do They Work
Summary
1. Ecology is the study of connections in nature. 2. Life on earth is sustained by the one-way flow of high-quality energy from the sun, by the cycling of matter, and by gravity. 3. Matter, energy, and life are the major components of an ecosystem. 4. Energy in an ecosystem decreases in amount to each succeeding organism in a food chair or web. 5. Soil is a complex mixture of eroded rock, mineral nutrients, water, air, decaying organic matter, and billions of living organisms. It covers most of the earth and provides nutrients for plant growth. Soils are formed by a breaking down of rock, decomposing surface litter and organic matter. Bacteria and other decomposer microorganisms break down some of soil’s organic compounds into simpler inorganic compounds. 6. Matter is recycled through the earth’s ecosystem of air, land, water, and living organisms. This vast global recycling system is composed of nutrient cycles. 7. Scientists study ecosystems through the use of aquarium tanks, greenhouses, and controlled indoor and outdoor chambers. Specific variables are carefully controlled, like temperature, light, carbon dioxide, and humidity. 8. Two principles of sustainability found from learning how nature works are the law of conservation of matter and the two laws of thermodynamics.
Outline
3-1 What is ecology? CORE CASE STUDY. Tropical rainforests make up only 2% of the earth’s land surface, but account for more than half of all biodiversity. Already more than half of this area has been destroyed, and degradation is increasing. This will cause a reduction in biodiversity, an increase in climate change, and changes in regional weather patterns.
B. Ecology is the study of connections in the natural world.
1. An organism is any form of life. The cell is the basic unit of life in organisms.
2. Organisms are classified as either eukaryotic or prokaryotic based on the presence or absence of a membrane-bound nucleus.
3. Organisms are classified into species, which groups organisms similar to each other together.
4. Sexually reproducing organisms are classified as a species if, under natural conditions, they can potentially breed with one another and produce live, fertile offspring.
5. The tiny microbes rule the world; they are unseen by the naked eye but keep the natural world operating.
6. About 1.4 million species have been identified, but estimates of number of species range from 3.6 million to 100 million.
C. A population consists of a group of interacting individuals of the same species occupying a specific area. Genetic diversity explains why these individuals may not behave nor look exactly alike. The habitat is the place where a population or an individual usually lives. Its distribution or range is the area over which a species may be found. D. A community represents populations of different species living and interacting in a specific area. A biological community consists of all the populations of different species interacting and living in a specific area; this is a network of plants, animals, and microorganisms. SCIENCE FOCUS: the importance of insects in maintaining the environmental balance.
E. An ecosystem is a community of different species interacting with each other and with their nonliving environment of matter and energy. All of the earth’s diverse ecosystems comprise the biosphere. 3-2 What keeps us and other organisms alive?
A. Various interconnected spherical layers make up the earth’s life-support system. 1. The atmosphere is the thin membrane of air around the planet. 2. The troposphere is the air layer about 11 miles above sea level. 3. The stratosphere lies 11–30 miles above the troposphere and filters the sun’s harmful radiation. 4. The hydrosphere consists of earth’s water, found in liquid water, ice, and water vapor. 5. The lithosphere is the
