Protist Kingdom

Douglas Wilkin, Ph.D. Jean Brainard, Ph.D.

Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required) AUTHORS Douglas Wilkin, Ph.D. To access a customizable version of this book, as well as other Jean Brainard, Ph.D. interactive content, visit www.ck12.org

CK-12 Foundation is a non-proﬁt organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-source, collaborative, and web-based compilation model, CK-12 pioneers and promotes the creation and distribution of high-quality, adaptive online textbooks that can be mixed, modiﬁed and printed (i.e., the FlexBook® textbooks).

The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by federal, state, and international laws.

Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms.

Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons Attribution-Non-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as amended and updated by Creative Com- mons from time to time (the “CC License”), which is incorporated herein by this reference.

Complete terms can be found at http://www.ck12.org/about/ terms-of-use.

Printed: November 17, 2015 www.ck12.org Chapter 1. Protist Kingdom

CHAPTER 1 Protist Kingdom

• Describe the protist kingdom.

Prokaryote or eukaryote? This organism consists of a single cell with several ﬂagella. Is it a prokaryote, such as a bacterium? Actually, it’s larger than a prokaryotic cell, and it also has a nucleus. Therefore, this organism belongs to the domain Eukarya, the domain that includes humans. This particular eukaryote is one of the smallest, simplest organisms in the domain, called a protist. It’s scientiﬁc name is Giardia lamblia. As a human parasite, it can make us sick.

Kingdom Protista

Protists are a group of all the eukaryotes that are not fungi, animals, or plants. As a result, it is a very diverse group of organisms. The eukaryotes that make up this kingdom, Kingdom Protista, do not have much in common besides a relatively simple organization. Protists can look very different from each other. Some are tiny and unicellular, like an amoeba, and some are large and multicellular, like seaweed. However, multicellular protists do not have highly specialized tissues or organs. This simple cellular-level organization distinguishes protists from other eukaryotes, such as fungi, animals, and plants. There are thought to be between 60,000 and 200,000 protist species, and many have yet to be identified. Protists live in almost any environment that contains liquid water. Many protists, such as the algae, are photosynthetic and are vital primary producers in ecosystems. Other protists are responsible for a range of serious human diseases, such as malaria and sleeping sickness. The term protista was first used by Ernst Haeckel in 1866. Protists were traditionally placed into one of several groups based on similarities to a plant, animal, or fungus: the animal-like protozoa, the plant-like protophyta (mostly algae), and the fungus-like slime molds and water molds. These traditional subdivisions, which were largely based on non-scientific characteristics, have been replaced by classifications based on phylogenetics (evo- lutionary relatedness among organisms). However, the older terms are still used as informal names to describe the general characteristics of various protists.

1 www.ck12.org

FIGURE 1.1 Protists range from single-celled amoe- bas to multicellular seaweed. Protists may be similar to animals, plants, or fungi.

Summary

• Kingdom Protista includes all eukaryotes that are not animals, plants, or fungi. • Kingdom Protista is very diverse. It consists of both single-celled and multicellular organisms.

Explore More

Use this resource to answer the questions that follow.

• Kingdom Protista at http://www.biologycorner.com/lesson-plans/phyla/kingdom-protista/.

1. List three characteristics of protists. 2. How are protists classiﬁed? 3. What is another name for animal-like protists and plant-like protists? 4. Complete this statement: Any eukaryote that is not a plant, animal or fungus is a ______.

Review

1. What are protists? 2. How are unicellular protists and multicellular protists similar? 3. How are protists classiﬁed? What are the main categories of protists?

References

1. Laura Guerin. Diversity of protists . CC BY-NC 3.0