Chapter 27 BB Biological Science (PDF)

Biological Science Seventh Edition Chapter 27 Diversification of Eukaryotes Copyright © 2020, 2017, 2014 Pearson Ed...

Biological Science Seventh Edition Chapter 27 Diversification of Eukaryotes Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Chapter 27 Opening Roadmap Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Introduction (1 of 2) Domain Eukarya—third domain on tree of life Range from single-celled organisms the size of bacteria to sequoia trees and blue whales Eukaryotes are diverse, yet share fundamental features that distinguish them from bacteria and archaea: – Most are large, have more organelles, and more extensive cytoskeleton – Nuclear envelope – Multicellularity evolved multiple times – Asexual and sexual reproduction Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Introduction (2 of 2) Protists: – Protists include all eukaryotes except land plants, fungi, and animals – Have no defining features – Do not form a naturally occurring unified group – Tend to live in environments where they are surrounded by water most of the time, but can be found in a variety of environments – Protists are amazingly diverse in: ▪ Size, (from bacteria-sized to giant kelp) and morphology Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Figure 27.1 The Term “Protist” Refers to All Eukaryotes Except Land Plants, Fungi, and Animals Biologists study protists for three reasons: – They are important medically – They are important ecologically – They are critical to understanding the evolution of plants, fungi, and animals Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Impacts on Human Health and Welfare Several types of protists can cause human disease, and some also cause disease in our crops: – Irish potato famine of 1845 – Caused by protist Phytophthora infestans: ▪ Type of water mold ▪ Led to emigration, and mass starvation caused deaths Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Malaria Malaria: – One of the world’s worst chronic infectious diseases – Caused by five species of parasitic protist Plasmodium: ▪ Transferred to humans from Plasmodium Lives in Mosquitoes and in Huma mosquitoes Where It Causes Malaria – Cell types that make up each stage of Plasmodium’s life cycle are each specialized for infecting a specific host Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Table 27.1 Some Human Health Problems Caused by Protists Species Disease Five species of Plasmodium, These organisms cause malaria. Over 3.4 billion people (roughly primarily P. falciparum and P. vivax one-half of the world’s population) live in areas at risk of malaria transmission. Naegleria fowleri Brain-eating amoeba causes meningoencephalitis; infections are almost always fatal. Toxoplasma gondii Toxoplasmosis may cause eye and brain damage in infants and in AIDS patients. Many species of dinoflagellates Toxins released during harmful algal blooms accumulate in shellfish and poison people if eaten. Trypanosoma gambiense and T. Trypanosomiasis (“sleeping sickness”) is a potentially fatal disease rhodesiense transmitted through bites from tsetse flies. Occurs in Africa. Trypanosoma cruzi Chagas disease affects 6–7 million people and causes 50,000 deaths annually, primarily in South and Central America. Entamoeba histolytica Amoebic dysentery results in severe diarrhea and subsequent dehydration. Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Harmful Algal Blooms Bloom occurs when unicellular species’ population grows rapidly and reaches high densities in aquatic environment: – Caused by photosynthetic, toxin-producing protists called dinoflagellates – Rapid growth of some dinoflagellates is responsible for causing “red tides,” (caused by blooms of dinoflagellates) which can be toxic to humans – Harmful to humans because toxins build up in clams and other shellfish: ▪ Shellfish are typically not harmed ▪ But humans eating shellfish Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Protists Play a Key Role in Aquatic Food Chains (1 of 2) Photosynthetic protists take in CO2 from atmosphere and reduce (“fix”) it to form sugars Primary producers—species that produce chemical energy by photosynthesis Production by marine protists represents almost half of total carbon dioxide that is fixed on Earth Plankton—diatoms and other small organisms that drift in the open oceans or lakes Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Protists Play a Key Role in Aquatic Food Chains (2 of 2) A food chain describes nutritional relationships among organisms: – Many of the species at the base of food chains in aquatic environments are protists Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Could Protists Help Limit Global Climate Change? (1 of 3) Global carbon cycle: – Movement of carbon atoms from CO2 molecules in atmosphere to organisms on land or ocean and then back to atmosphere Researchers are trying to reduce global climate change by: – Decreasing CO2 concentrations in atmosphere – Increasing amount of carbon stored in aquatic and terrestrial environments Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved  Could Protists Help Limit Global Climate Change? (2 of 3) Protists play a key role in the global carbon cycle: – Act as carbon sinks: long- lived carbon repository: ▪ Sedimentary rocks: – From protists with shells made of calcium carbonate ▪ Petroleum: – Accumulation of dead bacteria, archaea, and protists at bottom of ocean Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Could Protists Help Limit Global Climate Change? (3 of 3) Recent research shows that fertilizing the ocean with iron may speed up carbon cycle: – Protist populations increase – Movement of carbon into carbon sinks increases – Atmospheric CO2 concentrations decrease Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved 27.2 How Do Biologists Study Protists? Protists have been the focus of intense study, but it is difficult to find any overall patterns in their evolution: – Eukaryotic lineages split over a billion years ago – There has been a great deal of divergence among protists: ▪ No synapomorphies (shared derived trait) Protists do not make up a monophyletic group; instead, they are a paraphyletic group- Do not share derived characteristics that set them apart from all other lineages Data on morphology and phylogenetic analyses of Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Microscopy: Studying Cell Structure (1 of 2) Studies show that protists can be grouped according to their overall cell structure and/or distinctive organelles Both light and electron microscopy allowed researchers to identify characteristics of specific lineages: – For example, stramenopiles have unusual flagella covered with hollow, hairlike structures Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Microscopy: Studying Cell Structure (2 of 2) Seven major groups of eukaryotes have been identified on the basis of diagnostic morphological characteristics Table 27.2: – Land plants, fungi, and animals represent subgroups within the two of the seven major eukaryotic lineages Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Table 27.2 Distinguishing Features (Synapomorphies) of Major Lineages of Eukaryotes Lineage Distinguishing Morphological Features (Synapomorphies) Amoebozoa Cells lack cell walls. When portions of the cell extend outward to move the cell, they form large lobes. Opisthokonta Reproductive cells have a single flagellum at their base. The cristae inside mitochondria are flat, not tube shaped as in other eukaryotes. This lineage includes protists as well as the fungi and the animals. (Fungi and animals are discussed separately in Chapters 29–32.) Excavata Most cells have a pronounced “feeding groove” where prey or organic debris is ingested. Most species lack typical mitochondria, although genes derived from mitochondria are found in the nucleus. Plantae Cells have chloroplasts with a double membrane. (The diversity of green algae and land plants is covered in Chapter 28.) Rhizaria Cells lack cell walls, although some produce an elaborate shell-like covering. When portions of the cell extend outward to move the cell, they are threadlike in shape. Alveolata Cells have sac-like structures called alveoli that form a continuous layer just under the plasma membrane. Alveoli are thought to provide support. If flagella are present, cells usually have two—one of which is covered with hairlike Stramenopila projections. Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Evaluating Molecular Phylogenies Morphological data and DNA sequence data suggest that seven groups are monophyletic Phylogenetic tree of the seven eukaryotic lineages shows that: – The Opisthokonta and Amoebozoa form the monophyletic group Unikonta (one tailed) – The other five major lineages form the monophyletic group Bikonta (two tailed) One hypothesis suggests that original split occurred between unikonts Copyright © 2020, and Education, Inc. All Rights Reserved 2017, 2014 Pearson Discovering New Lineages via Direct Sequencing Direct sequencing is based on: – Sampling soil or water – Analyzing DNA sequence of specific genes sample – Using data to place organisms in sample on a phylogenetic tree Subsequent work confirmed existence of many, diverse species called picoplankton Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved What Morphological Innovations Evolved in Protists? Earliest eukaryotes were probably single-celled organisms with: – Mitochondria – Nucleus and endomembrane system – Cytoskeleton – No cell wall These cells probably swam using a novel type of flagellum Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Endosymbiosis and the Origin of the Mitochondria (1 of 3) Mitochondria—organelles that generate ATP Endosymbiosis theory: – Mitochondria originated when bacterial cell took up residence inside another cell about 2 billion years ago Symbiosis—when individuals of two different species live in physical contact Endosymbiosis—when an Proposed Initial Steps in the organism of one species lives Evolution of the Mitochondria inside the cells of an organism of another species Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Endosymbiosis and the Origin of the Mitochondria (2 of 3) Observations consistent with endosymbiosis theory: – Mitochondria similar size to α-proteobacteria – Mitochondria replicate by fission, as do bacteria – Mitochondria have their own ribosomes and manufacture their own proteins – Mitochondria have double membranes, consistent with the engulfing mechanism – Mitochondria have their own genomes: ▪ Organized as circular molecules, like bacterial chromosomes Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Endosymbiosis and the Origin of the Mitochondria (3 of 3) Phylogenetic data support endosymbiosis theory: – Mitochondrial gene sequences more closely related to sequences from α-proteobacteria than to sequences from nuclear DNA of eukaryotes Genes from endosymbiotic bacterium moved into nuclear genome via lateral gene transfer Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Endosymbiosis and the Origin of Chloroplasts (1 of 3) All photosynthetic protists have chloroplasts: – Hypothesis: ▪ Eukaryotic chloroplast originated when protist engulfed a cyanobacterium ▪ Once inside the protist, photosynthetic bacteria provided host with oxygen and glucose ▪ Host provide bacterium protection and access to light Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Endosymbiosis and the Origin of Chloroplasts (2 of 3) Support for endosymbiosis hypothesis for origin of chloroplast in eukaryotes: – Chloroplasts have bacteria-like characteristics – Chloroplasts have circular DNA with genes similar to those in cyanobacteria – Peptidoglycan in cell wall – Extant endosymbiotic cyanobacteria live in cells of protists and animals Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Endosymbiosis and the Origin of Chloroplasts (3 of 3) Biologists hypothesize that endosymbiosis leading to photosynthesis first occurred in common ancestor of the Plantae: – This ancestor gave rise to all Plantae subgroups Chloroplasts also occur in four other major protist lineages: – In these species, chloroplasts are surrounded by more than two membranes Hypothesis: Ancestor of these Secondary Endosymbiosis Leads to Organelles with Four protists acquiredCopyright their© 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Membranes Figure 27.10 Photosynthesis Arose in Eukaryotes by Primary Endosymbiosis and Then Spread among Lineages via Secondary Endosymbiosis Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved  The Nuclear Envelope (1 of 2) Leading hypothesis for origination of nuclear envelope: – Derived from infoldings of plasma membrane – Infoldings would have given rise to endoplasmic reticulum (ER) at the same time Evidence for this hypothesis includes: – Infoldings of plasma membrane are found in some extant bacteria – Nuclear envelope and Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved The Nuclear Envelope (2 of 2) Nuclear envelope was advantageous: – Separated transcription and translation Nuclei diversified, leading to unique types of nuclei in major protist lineages Distinctive structure of nucleus is synapomorphy that distinguishes these lineages as distinct monophyletic groups Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Structures for Support and Protection Great variation in presence and nature of structures that provide support and protection for protists: – Cell walls: ▪ Diatoms are surrounded by glass-like cell wall of silicon dioxide ▪ Dinoflagellates have cell wall made of cellulose plates – Hard external shells – Rigid structures inside the plasma membrane – Diversification of protists associated with evolution of innovative structures for2017, Copyright © 2020, support 2014 Pearson Education, Inc. All Rights Reserved Multicellularity Multicellularity—organisms with more than one cell Mutations leading to multicellularity probably first caused cells to stick together after cell division: – Selection pressures acting on larger, colonial organisms allowed them to evolve and diversify – Eventually, cells became specialized for different functions: ▪ Not all cells express the same genes Multicellularity arose independently in a wide array of eukaryotic lineages Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved How Do Protists Obtain Food? (1 of 2) Bacteria and archaea obtain their food in a wide variety of ways: – Many protists ingest their food – They eat bacteria, archaea, or other protists whole: ▪ This process is called phagocytosis ▪ When phagocytosis occurs, individual takes in packets of food much larger than individual molecules Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved How Do Protists Obtain Food? (2 of 2) Protists feed in various ways: 1. Ingesting packets of food 2. Absorbing organic molecules directly from environment 3. Performing photosynthesis 4. Some species are mixotrophs; they can be autotrophic or heterotrophic depending on the environmental conditions, i.e. when sunlight is unavailable they can become heterotrophic by absorbing organic nutrients from their environment. Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Ingestive Feeding (1 of 2) Ingestive lifestyles: – Based on eating live or dead organisms or on scavenging loose bits of organic debris Some protists are large enough to surround and ingest bacteria and archaea Some protists are large enough to ingest other protists or microscopic animals Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Ingestive Feeding (2 of 2) Ingestive Feeding Feeding by phagocytosis is possible in protists that lack a cell wall: – Flexible membrane and dynamic cytoskeleton allow them to surround and “swallow” prey with pseudopodia (long, fingerlike projections) Many ingestive feeders actively hunt prey Other ingestive feeders attach themselves to a surface: – These protists feed by sweeping food particles into their mouth with Copyright © cilia 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Absorptive Feeding Absorptive feeding—nutrients taken up across plasma membrane, directly from the environment: – Common among protists Some absorptive feeders are decomposers: – Feeding on dead organic matter, or detritus Many absorptive feeders live inside other organisms: – If an absorptive species damages its host, it’s called a parasite Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Photosynthesis Autotrophic protists: – Produce organic compounds via photosynthesis – Range in size from single-cell organisms to giant seaweeds – Use carbon dioxide as primary source of carbon Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved How Do Protists Move? (1 of 2) Many protists actively move to find food or light Amoeboid motion: – Sliding movement observed in some protists accomplished by streaming of pseudopodia: ▪ Requires ATP ▪ Related to muscle movement in animals ▪ Key immune system cells in humans use amoeboid motion ▪ Amoeboid Motion Is Possible in Species That Lack Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved How Do Protists Move? (2 of 2) Other major mode of locomotion involves swimming via flagella or cilia Flagella and cilia have identical structures, however: – Flagella are long and are usually found alone or in pairs – Cilia are short and numerous Even closely related protists can use radically different formsCopyright of locomotion © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved How Do Protists Reproduce? Asexual reproduction: – Based on: ▪ Mitosis and cell division in eukaryotic organisms ▪ Fission in bacteria and archaea – Results in daughter cells that are genetically identical to the parent Sexual reproduction: – Based on meiosis and fusion of gametes – Results in daughter cells that are genetically different from their parents and from each other Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Sexual Versus Asexual Reproduction Meiosis: – Adaptive because genetically variable offspring may be able to thrive if the environment changes Genotypes of many parasites and pathogens evolve very quickly: – Natural selection favors host individuals with new genotypes that may be able to resist these parasites and pathogens Many biologists view sexual reproduction as an adaptation to fight disease Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Life Cycles—Haploid Versus Diploid Dominated (1 of 2) Life cycle: – Describes sequence of events that occur as individuals grow, mature, and reproduce Evolution of meiosis: – Introduced new event in protist life cycle – Created distinction between haploid and diploid phases of protist life cycle Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Life Cycles—Haploid Versus Diploid Dominated (2 of 2) Bacteria and archaea are always haploid: – In contrast, virtually, every aspect of life cycle is variable among protists To analyze a life cycle: – Start with fertilization—fusion of two gametes to form diploid zygote – Then trace what happens to zygote Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Figure 27.16a Life Cycles Vary Widely among Unicellular Protists Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Figure 27.16b Life Cycles Vary Widely among Unicellular Protists Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Life Cycles—Alternation of Generations Alternation of generations: – One phase of life cycle based on haploid form and another based on diploid form – Gametophyte—multicellular haploid form: ▪ Specialized cells produce gametes (single haploid cells) by mitosis and cell division – Two gametes fuse to produce a diploid zygote – Sporophyte: ▪ Multicellular diploid form: – Specialized cells that produce haploid cells (spores) via meiosis – Spores: Single haploid cells that divide mitotically to form haploid gametophyte Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Figure 27.17a Alternation of Generations Occurs in Many Multicellular Protists Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Figure 27.17b Alternation of Generations Occurs in Many Multicellular Protists Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Web Activity: Alternation of Generations in Protists Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved 27.4 Key Lineages of Eukaryotes Each of the seven major Eukarya lineages has at least one distinctive morphological characteristic Once an ancestor evolved distinctive cell structure, its descendants diversified into a wide array of lifestyles Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Amoebozoa (1 of 2) Amoebozoa: – Lack cell walls and take in food by engulfing it – Move via amoeboid motion and produce large, lobe-like pseudopodia – Are abundant in freshwater habitats and in wet soils – Some are also parasites of humans and other animals Major subgroups: – Amoebae – Cellular slime molds – Plasmodial slime molds Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Table 27.3 Key Lineages of Eukaryotes (1 of 6) Blank Morphology and Movement Reproduction Relevance Lack cell walls; Both asexual Slime molds flexible and and sexual influence dynamic cell reproduction. nutrient cycling by membranes. Cellular slime feeding on Display amoeboid molds are microorganisms. movement with haploid Dictyostelium cytoplasmic dominant. discoideum is streaming. Plasmodial used as a model slime molds are organism for cell diploid biology. dominant. Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Amoebas They have lobe like pseudopods which they use to move and to feed. They contain digestive vacuoles which help to break down the food particles they take in by phagocytosis The contractile vacuole helps to expel excess water They reproduce asexually via fission Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Excavata (1 of 2) Excavata: – Have “excavated” feeding groove on one side of cell – The clade Excavata is characterized by its cytoskeleton – Some lack mitochondria, but ancestors are thought to have had them: ▪ Some have genes in nuclear genome of mitochondrial origin ▪ Some have vestigial mitochondria Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Excavata (2 of 2) Blank Morphology and Movement Reproduction Relevance Excavated feeding Primarily Trichomonas groove on side of asexual causes cell. reproduction. trichomoniasis. Most swim via Sexual Giardia is flagella. reproduction responsible for Diplomonads have has been giardiasis. two nuclei. observed in Euglenids are only a few abundant in Many euglenids members. are photosynthetic. freshwater plankton. Major subgroups: – Parabasalids – Diplomonads – Euglenids Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Plantae Plantae: – Monophyletic group – All subgroups descended from a common ancestor that engulfed a cyanobacterium- plastids arose when a heterotrophic protist acquired a cyanobacterial endosymbiont – The photosynthetic descendants of this ancient protist evolved into red algae and green algae – Plants are descended from the green algae Subgroups: – Glaucophyte algae – Red algae – Green algae – Land plants Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Table 27.3 Key Lineages of Eukaryotes (3 of 6) Blank Morphology and Movement Reproduction Relevance Algae can be Both asexual Primary producers unicellular, and sexual in most colonial, or reproduction. ecosystems. multicellular. Some algae Agar is derived Contain and all land from cell walls of chloroplasts. plants exhibit red algae. Cell walls alternation of Some red algae composed of generations. aid in development cellulose. of coral reefs. Algae produce flagellated cells. Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Red Algae Red algae are reddish in color due to an accessory pigment called phycoerythrin Some species lack pigmentation and function heterotrophically as parasites on larger red algae Red algae are usually multicellular; the largest are seaweeds Red algae are the most abundant large algae in coastal waters of the tropics Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Green Algae Green algae are named for their grass-green chloroplasts Plants and green algae are closely related Green algae are a paraphyletic group The two main groups are the charophytes and the chlorophytes Charophytes are most closely related to plants- in their ultrastructure and pigment composition Chlorophytes include unicellular, colonial, and multicellular forms Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Rhizaria Rhizaria: – Single-celled organisms that lack cell walls – Some species have elaborate shell-like coverings – Move by amoeboid motion and produce long, slender pseudopodia 11 major subgroups Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Radiolarians Radiolarians, mostly marine protists, have delicate, symmetrical internal skeletons that are usually made of silica Pseudopodia (known as axopodia) reinforced by microtubules Radiolarians use their pseudopodia to engulf microorganisms through phagocytosis A radiolarian showing numerous threadlike pseudopodia Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Forams Foraminiferans, or forams, are named for porous, generally multichambered shells, called tests made of calcium carbonate. Pseudopodia extend through the pores in the test and function in swimming, test formation and feeding Many forams have endosymbiotic algae. Some are also nourished by the photosynthetic activity of symbiotic algae living within their tests Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Alveolata (1 of 2) Alveolata: – Flattened, membrane-bound vesicles, called alveoli, located just under their plasma membranes – Unicellular, but diverse in morphology and lifestyle Some species are capable of bioluminescence: – Emit light via an enzyme-catalyzed reaction Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Alveolata (2 of 2) Blank Morphology and Movement Reproduction Relevance Contain vesicles Both asexual Dinoflagellates are called alveoli and sexual photosynthetic, and that support the reproduction. some are plasma bioluminescent. membrane. Apicomplexans are Move by cilia or parasites flagella. Some responsible for apicomplexans several diseases. move by amoeboid motion. Major subgroups: – Ciliates – Dinoflagellates – Apicomplexans Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Figure 27.18 Bioluminescent Dinoflagellates Light Up Ocean Waves at Night Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Ciliates Ciliates, a large varied group of protists, are named for their use of cilia to move and feed The cilia may completely cover their cell surface or be clustered in a few rows or tufts A distinctive feature is the presence of two types of nuclei: tiny micronuclei and large macronuclei. The macronucleus contains the genome and controls everyday functions such as feeding, waste removal and water balance. Genetic variation results from conjugation, in which two individuals exchange haploid micronuclei Conjugation is a sexual process, and is separate from reproduction, which generally occurs by binary fission. Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved  Cilia along a funnel-shaped oral groove move food Paramecium constantly takes in water (mainly bacteria) into the cell mouth, where the food is by osmosis from its hypotonic engulfed into food vacuoles by phagocytosis. environment. Bladderlike contractile vacuoles accumulate excess water from radial canals and periodically expel it through the plasma membrane. Food vacuoles fuse with lysosomes. As Thousands of cilia cover the the food is digested, the vacuoles follow surface of Paramecium. a looping path through the cell. Wastes are released when the vacuoles fuse with a specialized region of the plasma membrane that functions as an anal pore. Structure and function in the ciliate Paramecium caudatum. Feeding, waste removal and water balance. Stramenopila (Heterokonta) Stramenopila: – At some stage of life cycle, have flagella covered with distinctive hollow “hairs:” ▪ Synapomorphy This lineage includes a large number of unicellular forms, but some are multicellular: – Water molds – Diatoms – Brown algae Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Stramenopiles The clade Stramenopila includes some of the most important autotrophs on earth- such as algae It also includes several clades of heterotrophs Name of the clade is derived from the Latin for Stramen-straw and pilos-hair) which refers to a flagellum with numerous fine hairlike projections Most have a “hairy” flagellum paired with a “smooth” flagellum Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Diatoms Diatoms are unicellular algae with a unique two-part, glass-like wall of hydrated silica (silicon dioxide), embedded in an organic matrix. The walls consist of two parts that overlap like a shoe box and its lid. These walls provide protection from the crushing jaws of predators Diatoms are a major component of phytoplankton 40 μm The diatom Triceratium morlandii Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved Brown Algae Brown algae are the largest and most complex algae All are multicellular, and most are marine Brown algae include many species commonly called “seaweeds” Seaweeds have the most complex multicellular anatomy of all algae- some even have specialized tissues and organs that resemble those in plants Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved The algal body is plantlike but unlike plants, brown algae lack true tissues and organs - they lack true roots, stems, and leaves and is called a thallus Brown algal seaweeds have plantlike structures: the rootlike holdfast, which anchors the alga, and a stemlike stipe, which supports the leaflike blades Some have gas-filled, bubble- shaped floats to keep their photosynthetic structures near the water surface