An illustration of Classification of protist.

FIGURE 21–2 Protist Classification—A Work in Progress This cladogram represents an understanding of protist relationships supported by current research. Interpret Diagrams Which group of “protists” is most closely related to plants? Which group is most closely related to animals? To fungi?

d

Multiple Kingdoms? The most recent studies of protists divide them into six major clades, shown in Figure 21–2, each of which could be considered a kingdom in its own right. Where would that leave the plant, animal, and fungi kingdoms? Surprisingly, they fit right into these six clades, and two of them, animals and fungi, actually emerge from the same protist ancestors.

In a way, this should have been expected. Protists were the first eukaryotes, and evolution has had far more time to develop differences among protists than among more recently evolved eukaryotes like plants and animals. In other words, by finding the fundamental divisions among protists, we also identify the most basic differences among all eukaryotes. You should expect protist classification to change yet again as biologists learn more about the genomes of these remarkable organisms.

What “Protist” Means Today Today biologists assembling what is often called the Tree of Life favor the classification shown above. But the word “protist” remains in such common usage, even among scientists, that we continue to use it here. Bear in mind, however, that the “protists” are not a single kingdom but a collection of organisms that includes several distinct clades. This is why the term is sometimes surrounded by quotation marks.

For more on the diversity of protists, go to the Visual Guide. A sea shell.DOL•10–DOL•15

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Table of Contents

Miller & Levine Biology
About the Authors
Changing the World of Biology Education
Contents
Diversity of Life: A Visual Guide DOL•1–DOL•64
Labs and Activities
Features
UNIT 1 The Nature of Life
1 The Science of Biology
2 The Chemistry of Life
Unit Project
UNIT 2 Ecology
3 The Biosphere
4 Ecosystems and Communities
5 Populations
6 Humans in the Biosphere
Unit Project
UNIT 3 Cells
7 Cell Structure and Function
8 Photosynthesis
9 Cellular Respiration and Fermentation
10 Cell Growth and Division
Unit Project
UNIT 4 Genetics
11 Introduction to Genetics
12 DNA
13 RNA and Protein Synthesis
14 Human Heredity
15 Genetic Engineering
Unit Project
UNIT 5 Evolution
16 Darwin's Theory of Evolution
17 Evolution of Populations
18 Classification
19 History of Life
Unit Project
UNIT 6 From Microorganisms to Plants
20 Viruses and Prokaryotes
21 Protists and Fungi
22 Introduction to Plants
23 Plant Structure and Function
24 Plant Reproduction and Response
Unit Project
UNIT 7 Animals
25 Introduction to Animals
26 Animal Evolution and Diversity
27 Animal Systems I
28 Animal Systems II
29 Animal Behavior
Unit Project
UNIT 8 The Human Body
30 Digestive and Excretory Systems
31 Nervous System
32 Skeletal, Muscular, and Integumentary Systems
33 Circulatory and Respiratory Systems
34 Endocrine and Reproductive Systems
35 Immune System and Disease
Unit Project
A Visual Guide to The Diversity of Life
HOW TO USE THIS GUIDE
THE TREE OF LIFE
Bacteria
Protists
Fungi
Plants
Animals
Appendices
Appendix A Science Skills
Appendix B Lab Skills
Appendix C Technology & Design
Appendix D Math Skills
Appendix E Periodic Table
Glossary
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q, R
S
T
U
V
W
X, Y, Z
Index
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Credits
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