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Protists and Fungi CHAPTER 1 Protists and Fungi CHAPTER OUTLINE 1.1 Protist Characteristics 1.2 Protists Nutrition 1.3 Animal-like Protists 1.4 Plant-like Protists 1.5 Fungus-like Protists 1.6 Importance of Protists 1.7 Fungi 1.8 Symbiotic Relationships of Fungi 1.9 Fungi Structure 1.10 Fungi Reproduction 1.11 Fungi Classification 1.12 Human Uses of Fungi 1.13 References Introduction Would you eat this mushroom? Now that’s an interesting mushroom! In fact, fungi can be some of the most colorful species. And protists can be some of the most interesting. These two kingdoms are the first two eukaryotic kingdoms we discuss, and they have some of the most diverse members. 1 www.ck12.org But this mushroom? Probably not a good idea to eat. This is a poisonous and psychoactive fungus. With its large, white-gilled, white-spotted, usually deep red appearance, it is one of the most recognizable and widely encountered mushrooms in popular culture. However, you shouldn’t eat it! 2 www.ck12.org Chapter 1. Protists and Fungi 1.1 Protist Characteristics • Describe the main features of the protists. • Explain protist classification. Animal? Bacteria? Plant? Fungi? What do these figures represent? None of the above! These organisms may be single-celled like bacteria, and they may look like a fungus. They also may hunt for food like an animal or photosynthesize like a plant. And, yet, they do not fit into any of these groups. These organisms are protists! What are Protists? Protists are eukaryotes, which means their cells have a nucleus and other membrane-bound organelles. Most protists are single-celled. Other than these features, they have very little in common. You can think about protists as all eukaryotic organisms that are neither animals, nor plants, nor fungi. Although Ernst Haeckel set up the Kingdom Protista in 1866, this kingdom was not accepted by the scientific world until the 1960s. These unique organisms can be so different from each other that sometimes Protista is called the “junk drawer" kingdom. Just like a junk drawer, which contains items that don’t fit into any other category, this kingdom contains the eukaryotes that cannot be put into any other kingdom. Therefore, protists can seem very different from one another. 3 1.1. Protist Characteristics www.ck12.org Unicellular or Multicellular? Most protists are so small that they can be seen only with a microscope. Protists are mostly unicellular (one-celled) eukaryotes. A few protists are multicellular (many-celled) and surprisingly large. For example, kelp is a multicellular protist that can grow to be over 100-meters long ( Figure 1.1). Multicellular protists, however, do not show cellular specialization or differentiation into tissues. That means their cells all look the same and, for the most part, function the same. On the other hand, your cells often are much different from each other and have special jobs. FIGURE 1.1 Kelp is an example of a muticellular pro- tist. Characteristics of Protists A few characteristics are common between protists. 1. They are eukaryotic, which means they have a nucleus. 2. Most have mitochondria. 3. They can be parasites. 4. They all prefer aquatic or moist environments. Classification of Protists For classification, the protists are divided into three groups: 1. Animal-like protists, which are heterotrophs and have the ability to move. 2. Plant-like protists, which are autotrophs that photosynthesize. 3. Fungi-like protists, which are heterotrophs, and they have cells with cell walls and reproduce by forming spores. But remember, protists are not animals, nor plants, nor fungi ( Figure 1.2). Vocabulary • eukaryote: Organism with cells (or cell) that have a nucleus and membrane-bound organelles. • protist: Eukaryote that is not a plant, animal, or fungus. 4 www.ck12.org Chapter 1. Protists and Fungi FIGURE 1.2 Protists come in many different shapes. Summary • Protists are a diverse kingdom, including all eukaryotic organisms that are neither animals, nor plants, nor fungi. • For classification, the protists are divided into three groups: animal-like protists, plant-like protists, and fungi- like protists. Explore More Use the resource below to answer the questions that follow. • Protists at http://www.youtube.com/watch?v=8deF3Rw4ti4 (5:07) MEDIA Click image to the left for use the URL below. URL: http://gamma.ck12.org/flx/render/embeddedobject/57448 1. What defines the Kingdom Protista? 2. Are relationships between protists clearly defined? Why or why not? 3. What are phototrophs? How do they obtain their food? Give an example. 4. What are organotrophs? 5. Do all protists reproduce in the same manner? Explain. 5 1.1. Protist Characteristics www.ck12.org Explore More Answers 1. The Kingdom Protista is not clearly defined. It contains all eukaryotes that are not plants, animals or fungi. 2. Relationships between protists are not clearly defined. 3. Phototrophs make their own food, usually using energy from the sun. Kelp is an example. 4. Organotrophs feed on other organisms to obtain energy. 5. No, all protists do not reproduce in the same manner. Some reproduce asexually, and others reproduce sexually. Others yet reproduce both sexually and asexually. Review 1. What do all protists tend to have in common? 2. How are protists generally classified? 3. What can generally be said about the environments of protists? 4. Why is the Kingdom Protista referred to as the "junk drawer" kingdom? Review Answers 1. Protists are eukaryotes, which means their cells have a nucleus and other membrane-bound organelles. That is about all they all have in common. 2. Protists are classified as being animal-like, plant-like, or fungi-like. 3. Protists all prefer aquatic or moist environments. 4. The Kingdom Protista contains the eukaryotes that cannot be put into any other kingdom. 6 www.ck12.org Chapter 1. Protists and Fungi 1.2 Protists Nutrition • Describe how protists obtain food. • Explain endocytosis in protists. What can photosynthesize AND hunt for food? No, there are no man-eating plants or leaf-growing animals. The idea of an organism both photosynthesizing and hunting for food might seem strange, but this isn’t science fiction. These organisms, examples of Euglena, are protists that can feed like an animal or use the energy of the sun to make food like a plant. Protists Nutrition The cells of protists need to perform all of the functions that other cells do, such as grow and reproduce, maintain homeostasis, and obtain energy. They also need to obtain "food" to provide the energy to perform these functions. Recall that protists can be plant-like, fungi-like, or animal-like. That means that protists can obtain food like plants, fungi, or animals do. There are many plant-like protists, such as algae, that get their energy from sunlight through photosynthesis. Some of the fungus-like protists, such as the slime molds ( Figure 1.3), decompose decaying matter. The animal-like protists must "eat" or ingest food. Some animal-like protists use their "tails" to eat. These protists are called filter-feeders. They acquire nutrients by constantly whipping their tails, called flagellum, back and forth. The whipping of the flagellum creates a current that brings food into the protist. 7 1.2. Protists Nutrition www.ck12.org Other animal-like protists must "swallow" their food through a process called endocytosis. Endocytosis happens when a cell takes in substances through its membrane. The process is described below: 1. The protist wraps around its prey, which is usually bacteria. 2. It creates a food vacuole, a sort of "food storage compartment," around the bacteria. 3. The protist produces toxins which paralyze its prey. 4. Once digested, the food material moves through the vacuole and into the cytoplasm of the protist. Also, some of the animal-like and fungi-like protists are parasitic and absorb nutrients meant for their host, harming the host in the process. FIGURE 1.3 Slime molds live on decaying plant life and in the soil.