1. Components of life and Ecosystems
Chapter 3-Ecosystems
Components of life and Ecosystems

2. 3-1 What Is Ecology? Cells are the most basic unit of life.
The notion that all living things are made of cells is called cell theory.
Large and complex organic compounds make up the molecular units found in cells.
A chromosome is a single strand of DNA and associated proteins.
Chromosomes contain genes, which are sequences of nucleotides that provide the cell with instructions for building proteins.

3. Genetic Diversity of a Caribbean Snail
Fig. 3-4, p. 41

4. Genetic Diversity of People
Fig. 3-4, p. 41

5. 3-1 Con’t
A species is a group of organisms that generally resemble one another in their appearance, behavior, chemistry, genetic makeup, and are able to mate and produce fertile offspring.
There are an estimated 4 to 100 million species of organisms on Earth.
Biologists have identified about 1.8 million species, about 54% of them insects.
Ecology is the study of connections in the natural world. Ecologists try to understand interactions among organisms, populations, communities, ecosystems, and the biosphere.
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.

6. 3-1 con’t
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.
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.
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.