18.3 Building the Tree of Life
What are the six kingdoms of life as they are now identified?- What does the tree of life show?
domain • Bacteria • Archaea • Eukarya
Concept Map As you read, construct a concept map describing the characteristics of the three domains.
THINK ABOUT IT The process of identifying and naming all known organisms, living and extinct, is a huge first step toward the goal of systematics. Yet naming organisms is only part of the work. The real challenge is to group everything, from bacteria to dinosaurs to blue whales, in a way that reflects their evolutionary relationships. Over the years, new information and ways of studying organisms have produced major changes in Linnaeus's original scheme for organizing living things.
Changing Ideas About Kingdoms
What are the six kingdoms of life as they are now identified?
During Linnaeus's time, the only known differences among living things were the fundamental characteristics that separated animals from plants. Animals were organisms that moved from place to place and used food for energy. Plants were green organisms that generally did not move and got their energy from the sun.
As biologists learned more about the natural world, they realized that Linnaeus's two kingdoms—Animalia and Plantae—did not reflect the full diversity of life. Classification systems have changed dramatically since Linnaeus's time, as shown in Figure 18–13. And hypotheses about relationships among organisms are still changing today as new data are gathered.
FIGURE 18–13 From Two to Six Kingdoms This diagram shows some of the ways in which organisms have been classified into kingdoms since the 1700s.
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Table of Contents
- Formulas and Equations
- Applying Formulas and Equations
- Mean, Median, and Mode
- Estimation
- Using Measurements in Calculations
- Effects of Measurement Errors
- Accuracy
- Precision
- Comparing Accuracy and Precision
- Significant Figures
- Calculating With Significant Figures
- Scientific Notation
- Calculating With Scientific Notation
- Dimensional Analysis
- Applying Dimensional Analysis