Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu To View the presentation as a slideshow with effects select “View”

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” To advance through the presentation, click the right-arrow key or the space bar. From the resources slide, click on any resource to see a presentation for that resource. From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. You may exit the slide show at any time by pressing the Esc key. How to Use This Presentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Protists Chapter 21 Table of Contents Section 1 Characteristics of Protists Section 2 Protist Diversity Section 3 Protists and Health

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Characteristics of Protists Objectives List the characteristics of protists. List three environments where protists can be found. Identify the unifying features of protists. Distinguish asexual and sexual reproduction of Chlamydomonas. Differentiate two ways multicellular protists reproduce sexually. Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Diversity Characteristics The kingdom Protista consists of an unusually diverse assortment of eukaryotes that exhibit a broad array of characteristics. Some protists are photosynthetic (like plants), some ingest food (like animals), and some absorb their food (like fungi). Protists are found almost everywhere there is water. Many live in lakes and oceans, floating as plankton or anchored to rocks. Section 1 Characteristics of Protists Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Diversity, continued The First Eukaryotes Protists—the first eukaryotes—are thought to have evolved about 1.5 billion years ago through the process of endosymbiosis. The kingdom Protista contains life-forms similar to those that gave rise to the three kingdoms of multicellular organisms—fungi, plants, and animals. Two important eukaryotic features that evolved among the protists are sexual reproduction and multicellularity. Section 1 Characteristics of Protists Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Diversity, continued What Unites Protists? The kingdom Protista contains all eukaryotes that cannot be classified as animals, plants, or fungi. The major phyla of protists are very different from one another and, with a few exceptions, are only distantly related. Historically, scientists have referred to heterotrophic protists as protozoa and to photosynthetic protists as algae. Section 1 Characteristics of Protists Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reproduction Reproduction in the unicellular green alga Chlamydomonas is typical of unicellular protists. As a mature organism, the single-celled protist is haploid. When it reproduces asexually, Chlamydomonas first absorbs its tail and divides by mitosis, producing two to eight haploid cells called zoospores, which remain within the wall of the parent cell. Section 1 Characteristics of Protists Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reproduction, continued Sexual Reproduction in Unicellular Protists During environmental stress, such as a shortage of nutrients, Chlamydomonas species reproduce sexually. The haploid cell divides by mitosis to produce gametes. After they are released, a pair of gametes from different individuals fuse to form a pair. This pair of gametes then shed their cell walls and fuse into a diploid zygote with a thick protective wall called a zygospore. Section 1 Characteristics of Protists Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reproduction, continued Sexual Reproduction in Multicellular Protists The reproductive cycle of Ulva, called alternation of generations, is characterized by two distinct multicellular phases. The diploid, spore-producing phase is called the sporophyte generation. The haploid, gamete-producing phase is called the gametophyte generation. The adult sporophyte alga has reproductive cells called sporangia, which produce haploid spores by meiosis. Section 1 Characteristics of Protists Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reproduction, continued Sexual Reproduction in Multicellular Protists Conjugation is the temporary union of two protists to exchange nuclear material. The process begins when two filaments align side by side. The nucleus of one cell then passes through the tube into the adjacent cell. The two nuclei eventually form a resting spore, which produces a new haploid filament. Section 1 Characteristics of Protists Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Protist Diversity Objectives Identify how amoebas and forams move. Describe the structure of diatoms. Contrast three kinds of algae. Differentiate three different kinds of flagellates. Summarize the general characteristics of a Paramecium. Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Ameboid Movement Amoebas Amoebas, members of the phylum Rhizopoda, are protists that move by using flexible, cytoplasmic extensions. These extensions are called pseudopodia from the Greek words pseudo, meaning “false,” and podium, meaning “foot.” During ameboid movement, a pseudopodium bulges from the cell surface, stretches outward, and anchors itself to a nearby surface. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Ameboid Movement, continued Foraminifera Members of the phylum Foraminifera, or forams, are marine protists that typically live in sand or attach themselves to other organisms or rocks. Forams are characterized by their porous shells, called tests. Long, thin projections of cytoplasm extend through the pores in the tests to aid in swimming and in catching prey. Some forams also obtain nourishment from algae that live symbiotically under their tests. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Algae Green Algae Most green algae (phylum Chlorophyta) are freshwater unicellular organisms, but some are large, multicellular marine organisms. They also exist as a major part of microscopic marine plankton, inhabit damp soil, or even thrive within the cells of other organisms as symbionts. Green algae contain the same pigments found in the chloroplasts of plants. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Algae, continued Red Algae Red algae (phylum Rhodophyta) are multicellular organisms found in warm ocean waters. Their red pigments are efficient at absorbing the light that penetrates deep waters. Red algae have a complex life cycle, usually involving alternation of generations. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Algae, continued Brown Algae Brown algae (phylum Phaeophyta) are multicellular and are found mostly in marine environments. The larger brown algae known as kelp grow along coasts and provide food and shelter for many different kinds of organisms. They are among the largest organisms on Earth. Brown algae reproduce by alternation of generations. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Diatoms Diatoms, members of the phylum Bacillariophyta, are photosynthetic, unicellular protists with unique double shells. Diatoms can have one of two types of symmetry: radial (like a wheel) or bilateral (two-sided). Diatoms secrete chemicals through holes in their shells, enabling them to move by gliding. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Flagellates Dinoflagellates Dinoflagellates, members of the phylum Dinoflagellata, are unicellular phototrophs, most of which have two flagella. Most dinoflagellates have a protective coat made of cellulose that is often encrusted with silica, giving them unusual shapes. Their flagella beat in two grooves—one encircling the body like a belt, the other perpendicular to it. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Flagellates, continued Euglenoids Euglenoids members of the phylum Euglenophyta, are freshwater protists with two flagella. A member of Euglena has a protein scaffold called a pellicle inside the cell membrane. A light-sensitive organ called the eyespot helps orient the movements of these organisms toward light. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Flagellates, continued Kinetoplastids Kinetoplastids, members of the phylum Kinetoplastida, are unicellular heterotrophs that have at least one flagellum, and some species have thousands. Kinetoplastids are clearly related to euglenoids, and many taxonomists merge the two phyla together. While most reproduce only asexually, some are known to produce gametes and reproduce sexually. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Flagellates, continued Ciliates Ciliates are the most complex and unusual of the protists. All members of the phylum Ciliophora have large numbers of cilia, tightly packed rows of short flagella used for movement. The body wall of ciliates is a tough but flexible outer pellicle that enables the organism to squeeze through or move around many obstacles. Reproduction in ciliates is usually by mitosis, with the body splitting in half. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Protistan Molds Cellular Slime Molds Cellular slime molds, members of the phylum Acrasiomycota, resemble amoebas but have distinct features. The individual organisms behave as separate amoebas, moving through the soil and ingesting bacteria. During environmental stress, the individual amoebas gather together and move toward a fixed center. There they form multicellular colonies called slugs. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Protistan Molds, continued Plasmodial Slime Molds Plasmodial slime molds, members of the phylum Myxomycota, are a group of organisms that stream along as a plasmodium, a mass of cytoplasm that looks like an oozing slime. A plasmodial slime mold contains many nuclei, but they are not separated by cell walls. If the plasmodium becomes stressed, it divides into many small mounds that produce stalks tipped with a capsule in which haploid spores develop. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Protistan Molds, continued Other Molds Oomycetes, members of the phylum Oomycota, are the water molds, white rusts, and downy mildews that often grow on dead algae and dead animals in fresh water. Oomycetes are unusual in that their spores have two flagella: one pointed forward, the other pointed backward. Many oomycetes are plant pathogens. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Sporozoans Parasitic protists that form spores during their reproduction cycle are called sporozoans. All sporozoans are parasitic and cause many serious diseases. Malaria, a sporozoan disease, kills more people than any other infectious disease. Sporozoans have complex life cycles that involve both asexual and sexual reproduction. Section 2 Protist Diversity Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Protists and Health Objectives Identify two ways that protists affect human health. Name three human diseases, other than malaria, caused by protists. Summarize how malaria is transmitted. Evaluate the methods used to control malaria. Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Protists and Humans One of the greatest effects protists have on humans is that they cause disease. Protists also affect humans through the diseases they cause in livestock. The added cost of treating diseased livestock is passed on to consumers in the form of higher meat prices. Section 3 Protists and Health Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Protists and Humans, continued Beneficial Protists Cattle could not digest the cellulose in the hay and grass they eat without the aid of commensal protists in their digestive tract. Protists are also the single largest group of photosynthesizers on the planet. Many protists are also detritivores, so they help recycle important chemicals, such as nitrogen, carbon, and phosphorus, in the environment. Section 3 Protists and Health Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Malaria Malaria is one of the most deadly diseases in humans. The symptoms include severe chills, fever, sweating, confusion, and great thirst. Victims die of anemia, kidney failure, or brain damage unless the disease is treated. Section 3 Protists and Health Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Malaria, continued Malaria Life Cycle Malaria is caused by several species of Plasmodium and is spread by the bite of certain mosquitoes. If the mosquito is infected with Plasmodium, it will also inject about 1,000 protists with its saliva. This infective stage of Plasmodium is called the sporozoite. Sporozoites infect the liver, where they rapidly divide and produce millions of cells of the second stage of the life cycle, called the merozoite. Section 3 Protists and Health Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Malaria, continued Treating and Preventing Malaria In the middle of the seventeenth century, quinine, a chemical derived from the bark of the cinchona tree was discovered to be a remedy for malaria. Derivatives of quinine, such as chloroquine and primaquine, are now used to treat malaria. Malaria can also be controlled by reducing mosquito populations. Section 3 Protists and Health Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice The chart below shows the daily temperature of a patient who has malaria. Use the chart to answer questions 1–3. Standardized Test Prep Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 1.This pattern of temperature variation occurs when Plasmodium merozoites infect and destroy A.liver cells. B.red blood cells. C.the digestive tract. D.the salivary glands. Standardized Test Prep Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 2.If the pattern continues, what will be the approximate temperature of the patient on Monday? F.37 ° C G.39 ° C H.41 ° C J.45 ° C Standardized Test Prep Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 2. If the pattern continues, what will be the approximate temperature of the patient on Monday? F.37 ° C G.39 ° C H.41 ° C J.45 ° C Standardized Test Prep Chapter 21

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 3. In this patient, the cycle of fever and chills repeats every A.12 hours. B.24 hours. C.48 hours. D.72 hours. Standardized Test Prep Chapter 21

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