21.1 Protist Classification—The Saga Continues
What are protists?- How are protists related to other eukaryotes?
Preview Visuals Look at the names of the organisms in Figure 21–2. Are any of the organisms familiar to you? Formulate two questions you have about this diagram.
THINK ABOUT IT about it Some of the organisms we call “protists” live quietly on the bottom of shallow ponds, soaking up the energy of sunlight. Others swim vigorously in search of tiny prey. Some sparkle like diamonds in coastal waters, and others drift in the human bloodstream, destroying blood cells and killing nearly a million people a year, most of them children. What kind of life is this, capable of such beauty and such destruction?
The First Eukaryotes
What are protists?
More than a billion years ago, a new form of organism appeared on Earth. Subtle clues in the microscopic fossils of these single cells mark them as the very first eukaryotes. Single-celled eukaryotes are still with us today and are often called “protists”—a name that means “first.” Traditionally, protists are classified as members of the kingdom Protista. Protists are eukaryotes that are not members of the plant, animal, or fungi kingdoms.
Although most protists are unicellular, quite a few are not. The largest protists—brown algae called kelp—contain millions of cells arranged in differentiated tissues. They are considered protists because they are related more closely to certain unicellular protists than to members of any other kingdom. Kelp and several other protists are shown in Figure 21–1.
In Your Notebook Think about the things that define a group. What do you think defines protists as a group?
FIGURE 21–1 Extreme Diversity of Protists Protists vary greatly in size, form, and function. Here are several examples.
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