4-1 The Nature of Ecology A. Ecology is the study of connections in the natural world. Ecologists try to understand interactions among organisms, populations, communities, ecosystems, and the biosphere. 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 group 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. B. 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. C. 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. D. 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.
4-2 The Earth’s Life-Support Systems A. Various interconnected spherical layers make up the earth’s life-support system. B. The atmosphere is the thin membrane of air around the planet. C. The troposphere is the air layer about 11 miles above sea level. D. The stratosphere lies above the troposphere between 11–30 miles; it filters out the sun’s harmful radiation. E. The hydrosphere consists of the earth’s water, found in liquid water, ice, and water vapor. F. The lithosphere is the crust and upper mantle of the earth’s soil. It contains nonrenewable fossil fuels, minerals, and soil, and renewable soil chemicals needed for plant life. G. The biosphere includes most of the hydrosphere, parts of the lower atmosphere, and upper lithosphere. All parts of the biosphere are interconnected. H. Ecology’s goal is to understand the interactions in the earth’s global skin of air, water, soil, and organisms. I. Sun cycles of matter and gravity sustain life on Earth. 1. The one-way flow of high-quality solar energy through materials and living things (as they eat) produces low-quality energy. Energy can’t be recycled. 2. Matter cycles through parts of the biosphere. 3. Gravity causes the downward movement of chemicals as matter cycles through the earth. J. Solar energy just passes through the earth as electromagnetic waves; they warm the atmosphere, evaporate and recycle water, generate wind, and support plant growth. K. As solar radiation interacts with the earth, infrared radiation is produced. Greenhouse gases trap the heat and warm the troposphere. This natural greenhouse effect makes the planet warm enough to support life. Energy from the sun supports photosynthesis. L. The earth’s temperatures, distance from the sun, and size all produce a livable planet. Its liquid water, orbit from the sun, and its gravitational mass all contribute to sustaining life in this natural greenhouse.
4-3 Ecosystem Components
A. Terrestrial parts of the biosphere are classified as biomes, areas such as deserts, forests, and grasslands. Aquatic life zones describe the many different areas found in a…