Chapter 16 The Origin and Evolution of Microbial

Chapter 16 The Origin and Evolution of Microbial Life: Prokaryotes and Protists http: //genomed. dlearn. kmu. edu. tw Power. Point Lectures for 生物醫學暨環境生物學系 Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon 張學偉助理教授 changhw@kmu. edu. tw Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

How Ancient Bacteria Changed the World • Mounds of rock found near the Bahamas

• Fossilized mats 2. 5 billion years old mark a time when photosynthetic prokaryotes – Were producing enough O 2 to make the atmosphere aerobic Stromatolites Rocklike structure composed of many layers of bacteria and sediments. 希臘文 Stroma- bed; litos- rock Layers of a bacterial mat Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

EARLY EARTH AND THE ORIGIN OF LIFE 16. 1 Life began on a young Earth • 宇宙起源學說「大爆炸」- The "big bang" - the universe is occurred sometime between 10 and 20 billion yrs ago. (wiki; 二○○六年諾貝爾物理學獎 ) • Planet Earth formed some 4. 6 billion years ago Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• The first early atmosphere probably contained - mostly hot H 2 (but hard to hold) • The secondly early atmosphere probably contained - H 2 O, CO 2, N 2, H 2 S and some CH 4 , NH 3 • Volcanic activity, lightning, and UV radiation were intense also in early Earth. Figure 16. 1 A Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Fossilized prokaryotes called stromatolites – Date back 3. 5 billion years (photosynthetic

• A clock analogy tracks the origin of the Earth to the present day major events and its life 補充 The geologic record is divided into: Three eons: Archaean, Proterozoic, Phanerozoic c zoi o r ne n a h P eo Cenoo s c e i zoic M zo c i o zo Humans ale P Land plants Origin of solar system and Earth Animals Many eras and periods http: //tw. knowledge. yahoo. co m/question/? qid=12050 81201537 Proterozoic Archaean eon Multicellular eukaryotes Figure 16. 1 C 4 1 Bil lio 2 ns go of a rs 3 a ye Prokaryotes Single-celled eukaryotes Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Atmospheric oxygen

Planet Earth • formed some 4. 6 billion years ago Prokaryotes • Appeared about 3. 5 billion years ago Oxygen production • Began about 2. 5 billion years ago Single-celled eukaryotic organisms • Evolved about 1. 7 billion years ago Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

16. 2 How did life originate? • Early - life arose spontaneously • 1600 s – large organism can’t do as early guess • 1860 s – Pasteur confirmed all life today arises only from preexisting life. However, no deal with the origin of life. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Most biologists hypothesis that the earliest life forms evolved from nonliving matter. • Life arose from nonorganic molecules present in Earth’s early oceans and atmosphere. • Organic molecules - May have been formed abiotically in the conditions on early Earth Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

TALKING ABOUT SCIENCE 16. 3 Stanley Miller’s experiments showed organic molecules could have arisen on a lifeless earth • 1920 s, Oparin and Haldane - proposed that organic chemistry could have evolved in early Earth’s environment because it contained no oxygen (a reducing environment). • An oxidizing environment (e. g. Earth’s O 2 -rich today) is corrosive. • A reducing environment tends to add electrons to molecules, building more complex forms from simple ones. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Figure 16. 3 A

(23 yr-graduate student) • In 1953, Miller tested this hypothesis using an artificial mixture of inorganic molecules (H 2 O, H 2, CH 4, and NH 3) in a laboratory environment that simulated conditions on early Earth. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Simulations of such conditions – Have produced amino acids, sugars, lipids, and the nitrogenous bases found in DNA and RNA “Atmosphere” CH 4 Water vapor Electrode How about Today’s updated Miller’s experiments? Better! NH 3 H 2 Condenser Which provided the chemicals required for the origin of life. Figure 16. 3 B Cold water Cooled water containing organic molecules H 2 O “Sea” early Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Sample for chemical analysis

16. 4 The first polymers may have formed on hot rocks or clay • Review: polymerization occurs by dehydration synthesis. (ch 3) • Organic polymers (e. g. proteins, nucleic acids) can make by: - (now) enzyme - (early Earth) hot clays (e- charge concentrate monomer, metallic atoms as catalysts) hot mineral surfaces (heat forces dehydration synthesis) Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

16. 5 The first genetic material and enzymes may both have been RNA - The hypothetical period is termed the RNA world Ribozymes - that catalyzed their own replication (the essential difference between cells and nonliving) – assemble spontaneously without cells or enzymes A G U G C G A A U G C A U G G C U U A C G U U C A G U U C C U A G U C G A Monomers Figure 16. 5 U 1 Formation of short RNA polymers: simple “genes” Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 2 Assembly of a complementary RNA chain, the first step in replication of the original “gene”

16. 6 Membrane-enclosed molecular cooperatives may have preceded the first cells Self-replication of RNA Self-replicating RNA acts as template on which polypeptide forms. Polypeptide Figure 16. 6 A Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Polypeptide acts as primitive enzyme that aids RNA replication. RNA

• Membranes may have separated various aggregates of self-replicating molecules LM 650 Polypeptides and lipids selfassemble into microscopic spheres called protobionts, fluid-filled droplets with semipermeable, membrane-like coatings. Figure 16. 6 B, C Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

If these cooperating molecules were incorporated into a protobiont, the basic structures for self-replicating cells would be present. Membrane RNA Which could be acted on by natural selection easy for growing and replicating Protobiont relies in the environment and diversity is favored. Figure 16. 6 C Polypeptide Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

PROKARYOTES 16. 7 Prokaryotes have inhabited Earth for billions of years • Prokaryotes are the oldest life-forms Colorized SEM 650 – And remain the most numerous and widespread organisms Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Size (diameters) Prokaryotes – 1 -5 m Eurkaryotes – 10 -100 m pathogen Figure 16. 7. Bacteria on the point of a pin

16. 8 Bacteria and archaea are the two main branches of prokaryotic evolution • Domains Bacteria and Archaea – Are distinguished on the basis of nucleotide sequences and other molecular and cellular features Greek archaios, ancient Past view – diverged from each other Current view – see next page Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Differences between Bacteria and Archaea In most features, archaea are more similar to eukaryotes than to bacteria. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Review: modern archaea and eukaryotes

16. 9 Prokaryotes come in a variety of shapes • Prokaryotes may be shaped as Curves or spirals bacillus Colorized SEM 9, 000 Colorized SEM 12, 000 coccus Rods (bacilli) spirochete Colorized SEM 3, 000 Spheres (cocci) Figure 16. 9 A–C • often occur in defined groups of two or more • in clusters - staphylococci. • in chains - streptococci. • usually occur unaggregated • in pairs - Diplobacilli • in chains - streptobacilli Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings • commas - Vibrios • spiral - spirilla and spirochetes. • Spirilla are shorter than spirochetes

16. 10 Various structural features contribute to the success of prokaryotes One of the most important features of nearly all prokaryotic cells- cell wall. • maintains cell shape, • provides physical protection • prevents the cell from bursting in a hypotonic environment Plasmolysis occurs in a hypertonic environment and prevents binary fission (reproduction). Thus, salting is a method of preserving food. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

External Structures Colorized TEM 70, 000 • The cell wall – Is one of the most important features of nearly all prokaryotes – Is covered by a sticky capsule Capsule Figure 16. 10 A Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

課本只有文字說明, 此圖補充可以涵蓋課文 Using a technique called the Gram stain • classify bacterial species into two groups based on cell wall composition: Gram-(+) and Gram-(-) Lipopolysaccharide (LPS) Cell wall Peptidoglycan layer Cell wall Outer membrane Peptidoglycan layer Plasma membrane Protein Grampositive bacteria Gramnegative bacteria 20 m (a) Gram-positive bacteria have a cell wall with a large amount of peptidoglycan that traps the violet dye in the cytoplasm. Figure 補充 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings (b) Gram-negative bacteria have less peptidoglycan, and it is located in a layer between the plasma membrane and an outer membrane.

• Some prokaryotes – Stick to their substrate with pili (fimbriae) Pili - are protein filaments thinner than bacterial flagella Sex pili are specialized fimbriae that are used to transfer plasmids from one bacterial cell to another (conjugation) (Review ch 10). Figure 16. 10 B Colorized TEM 16, 000 Pili Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Motility Many bacteria and archaea Flagellum Colorized TEM 14, 000 --> Are equipped with flagella, which enable them to move Flagella composed of protein Plasma Figure 16. 10 C in two membrane parts: 1. External, nonmembr anebounded filaments 注意: 單複數 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings without Cell wall Rotary movement of each flagellum

Reproduction and Adaptation • Prokaryotes – Have the potential to reproduce quickly (several hours or less) in favorable environments. – Bacteria multiply by binary fission and, under ideal conditions, divide once ever twenty minutes. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Some prokaryotes can withstand harsh conditions – By forming endospores Endospores are thick walls around a replicated copy of DNA and are extremely resistant to decomposition or disintegration. Figure 16. 10 D Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings TEM 34, 000 Endospore They can resist high temperatures; But autoclaves can kill endospores (steam at 121 o. C and 15 pounds of pressure for 15 to 20 minutes).

Internal Organization • Some prokaryotic cells – Have specialized membranes that perform metabolic functions Figure 16. 10 E Thylakoid membrane TEM 6, 000 TEM 45, 000 Respiratory membrane Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Aerobic prok. photosynthetic prok. Ribosomes size: Prok. < Euk. containing slightly different proteins and RNA. antibiotics that block protein Prokaryotic DNA synthesis in is smaller than bacteria and not eukaryotic DNA eukaryotes. (1/1000) and is usually circular. Plasmids

16. 11 Prokaryotes obtain nourishment in a variety of ways • As a group – Prokaryotes exhibit much more nutritional diversity than eukaryotes Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Types of Nutrition Autotrophs = self-feeders • Autotrophs make their own organic compounds from inorganic sources & only CO 2 as a carbon source. – Photoautotrophs harness sunlight for energy & use CO 2 for carbon – Chemoautotrophs obtain energy from inorganic chemicals instead of sunlight & use CO 2 for carbon Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Heterotrophs = other-feeders • Heterotrophs obtain their carbon atoms from organic compounds – Photoheterotrophs can obtain energy from sunlight – Chemoheterotrophs are so diverse that almost any organic molecule can serve as food for some species. e. g. E. coli. Figure 16. 11 A Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Nutritional classification of organisms Table 16. 11 Copyright © 2005 Pearson Education,

Metabolic Cooperation Colorized SEM 13, 000 • In some prokaryotes – Metabolic cooperation occurs in surfacecoating colonies called biofilms Copyright © 2005 SEM Pearson Education, Inc. Publishingplaque as Benjamin Cummings Colored for dental Figure 16. 11 B Cells in colonies secrete signals & recruit nearby cells. Internal cells use channels for nutrient and waste exchange.

16. 12 Archaea thrive in extreme environments— and in other habitats • Archaea are common in: Salt lakes, acidic hot springs, deep-sea hydrothermal vents • Archaea are also a major life-form in the ocean Figure 16. 12 A, B Great Salt Lake Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Yellowstone National Park

• Extreme halophiles - thrive in salty places, e. g. Great Salt Lake. • Extreme thermophiles - thrive in hot springs, deep-ocean vents), high-temperature, verylow-p. H environments, e. g. , Yellowstone National Park. • Methanogens - are a group of anaerobic, methane-producing bacteria. - production of marsh gas & flatulence in humans. - digest cellulose in the gut of animals. Archaea are turning up in environments that are not so extreme. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

16. 13 Bacteria include a diverse assemblage of prokaryotes Bacteria are currently organized into 9 groups: • • • Proteobacteria- 5 groups, Gram (-) bact. Chlamydias Spirochetes Gram (+) bact. Cyanobacteria Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Thiomargarita namibiensis, showing globules of sulfur wastes Colorized TEM 5, 000 Figure 16. 13 A, B LM 13, 000 Proteobacteria Bdellovibrio bacteriophorus (flagellated cell) attacking a larger bacterium • a subgroup - can fix atmospheric nitrogen in the nodules of legumes. Agrobacterium, is used in genetic engineering and produce plant tumors. • g subgroup (largest in the proteobacteria clade) - can oxidize sulfur (Fig. 16. 13 A). This group has many pathogens, e. g. Salmonella typhi and Vibrio cholera. E. coli. • d subgroup include the slime-secreting myxobacteria that aggregate to form fruiting bodies during times of stress, releasing resistant spores. Bdellovibrios (Fig. 16. 13 B). Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Chlamydias - are responsible for causing blindness and a common sexually transmitted disease called nongonococcal urethritis (非淋菌性尿道炎) Spirochetes - move like corkscrews. , e. g. spirochetes (Fig. 16. 9). - some are pathogens, Treponema pallidum (syphilis) and Borrelia burgdorferi (Lyme disease) Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Gram-positive bacteria - actinomycetes was once mistaken for fungus, found in soil and is a major source of antibiotics (Fig. 16. 13 C). -Staphylococcus and Streptococcus - common pathogens -Mycoplasma - the smallest living organism in this group. Streptomyces, the source of many antibiotics (colorized SEM) Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Colorized SEM 2, 800 Nitrogen-fixing cells Photosynthetic cells Figure 16. 13 C, D LM 650 Colorized SEM 2, 8000 Cyanobacteria, generating oxygen during photosynthesis. • cyanobacterium Anabaena

CONNECTION 16. 14 Some bacteria cause disease • Pathogenic bacteria cause disease by producing: Exotoxins or endotoxins Exotoxins are proteins secreted by prokaryotes. - Clostridium botulinum causes botulism (肉毒桿菌中毒). SEM 12, 000 Figure 16. 14 A Staphylococcus aureus, an exotoxin producer • Normal microbiota found in moist skin folds, but when it grows inside a person, its exotoxin cause toxic shock syndrome. • cause food poisoning • cause scalded skin syndrome Harmless bacteria can develop pathogenic strains Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Endotoxins are components of the outer membranes of some gram (-)bacteria. • The signs and symptoms from all endotoxins are the same: chills, fever, aches, weakness and decreased blood pressure that can lead to shock. • Salmonella species causes typhoid fever (傷寒) and food poisoning Copyright © 2005©Pearson Education, Inc. Publishing as publishing Benjamin Cummings Copyright 2002 Pearson Inc. , as Benjamin Cummings

• Three of our defenses against bacterial diseases: 1. Sanitation, 2. the use of antibiotics, 3. education. Spirochete that causes Lyme disease Prevention of Lyme disease is best accomplished through public education. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings “Bull’s-eye”rash SEM 2, 800 The cause of Lyme disease, Borrelia burgdorferi, is carried by a tick and elicits a distinctive set of symptoms and potential disorders. Tick that carries the Lyme disease bacterium Figure 16. 14 B 萊姆症(又稱萊姆關節炎, 由扁蝨傳染, 症狀有紅斑、頭疼、發燒等等)

CONNECTION 16. 15 Bacteria can be used as biological weapons Bacillus anthracis (炭疽桿菌), a spore-forming bacterium, causes anthrax • Animals, plants, fungi, and viruses have all served as weapons, but bacteria is the most frequent. • The route of infection determines the mortality rate. • Cutaneous (skin) anthrax is easy to treat, while pulmonary anthrax is treatable if detected early; • However, it is usually ignored as a common cold. Figure 16. 15 Cleaning up a site where anthrax spores were released in October 2001 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

CONNECTION 16. 16 Prokaryotes help recycle chemicals and clean up the environment • Bioremediation – Is the use of organisms to clean up pollution from water, soil, air Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Prokaryotes are decomposers in – Sewage treatment to remove toxic wastes – help mine – clean up oil spills Rotating spray arm Rock bed coated with aerobic bacteria and fungi Liquid wastes Outflow The trickling filter system at a sewage treatment plant Figure 16. 16 A, B aerobic and anaerobic communities of organisms Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Treatment of an oil spill in Alaska Natural bacteria or recombinant strains are used

PROTISTS 16. 17 The eukaryotic cell probably originated as a community of prokaryotes • Eukaryotic cells – Evolved from prokaryotic cells more than 2 billion years ago Two theories of how the membrane-enclosed organelles arose: • endomembrane • Symbiosis (endosymbiosis) Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• The nucleus and endomembrane system – Probably evolved from infoldings of the plasma membrane – membrane-bounded organelles except mitochondria and chloroplasts • Mitochondria and chloroplasts – Probably evolved from aerobic (alpha proteobacteria) and photosynthetic (cyanobacteria) endosymbionts, respectively Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Figure 16. 17 A model of the origin of eukaryotes (layer 1) Cytoplasm Plasma membrane Endoplasmic reticulum Ancestral prokaryote Nucleus Nuclear envelope Membrane infolding Aerobic heterotrophic prokaryote Cell with nucleus and endomembrane system Some cells Ancestral host cell Photosynthetic prokaryote Endosymbiosis Mitochondrion Chloroplast Mitochondrion Photosynthetic eukaryotic cell Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Figure 16. 17 A model of the origin of eukaryotes (layer 2) Cytoplasm Plasma membrane Endoplasmic reticulum Ancestral prokaryote Nucleus Nuclear envelope Membrane infolding Aerobic heterotrophic prokaryote Cell with nucleus and endomembrane system Some cells Ancestral host cell Photosynthetic prokaryote Endosymbiosis Mitochondrion Chloroplast Mitochondrion Photosynthetic eukaryotic cell Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

16. 18 Protists (單細胞生物) are an extremely diverse assortment of eukaryotes • Protists are diverse and represent several kingdoms within Domain Eukarya. (Old: protists kindom) LM 275 • Protists are found in all habitats but most common in aquatic. Figure 16. 18 Protists in pond water Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Protists are nutritionally diverse. Algae - Photosynthetic protists. Protozoa are heterotrophs that eat bacteria and other protists. Other protists are fungus-like.

• Protists are more complex than prokaryotes: a nucleus, organelles, and cilia & flagella (9+2). • The simplest eukaryotes, as most are single-celled organisms. Protists’ taxonomic groups are presented based on the most current information obtained from molecular and cellular studies. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

16. 19 A tentative phylogeny of eukaryotes includes multiple clades of protists Plants Closest algal relatives of plants Green algae Red algae Animals Choanoflagellates Fungi Cellular slime molds Plasmodial slime molds Amoebas Brown algae Diatoms Water molds Ciliates Apicomplexans Dinoflagellates Euglenozoans Diplomonads • The taxonomy of protists is a work in progress Kingdoms for plants, animals, fungi, and the groups that were once part of the Protista kingdom Alveolates Stramenopila Amoebozoa Figure 16. 19 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ancestral eukaryote

16. 20 Diplomonads (雙滴蟲類) and euglenozoans include some flagellated parasites • The parasitic Giardia – Is a diplomonad with highly reduced mitochondria (What makes Giardia particularly interesting is its lack of mitochondria) Colorized SEM 4, 000 • Diplomonads contain two nuclei and multiple flagella and are considered the most ancient living eukaryotic lineage. • Nutrition mode - Anaerobic heterotrophs • Drinking water contaminated with Giardia without boiling it first will lead to severe diarrhea. Figure 16. 20 A A diplomonad: Giardia intestinalis Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Euglenozoans- containing photosynthetic autotrophs (Euglena), heterotrophs (Euglena in dark), and pathogenic parasites (trypanosomes). Host: African tsetse fly A euglenozoan: Trypanosoma (with blood cells) (睡病蟲) Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings One or two flagella from one end of the cells Colorized SEM 1, 300 RBC Colorized SEM 1, 300 Alter molecular structure of coats frequently (antigenic variation) escape host immune system A euglenozoan: Euglena (眼蟲) Figure 16. 20 B, C

16. 21 Alveolates have sacs beneath the plasma membrane & include 1. dinoflagellates, 2. apicomplexans, and 3. ciliates • Dinoflagellates (二鞭毛藻)- are unicellular algae • Some dinoflagellates are responsible for toxin-releasing blooms in warm coastal waters that are known as red tides. cause extensive fish kills and harmful to humans. Figure 16. 21 A A dinoflagellate: Gymnodium Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings SEM 2, 300 two flagella in perpendicular grooves are uniquely shaped phytoplankton (浮游生物), found in both fresh and marine water.

Apicomplexans (頂覆蟲) are parasites • have an apical structure designed to penetrate the host. e. g. Plasmodium, which causes malaria An apicomplexan: Plasmodium Figure 16. 21 B 瘧原蟲 Apex TEM 26, 000 are spread by mosquitoes; reproduce inside red blood cells; cause the cells to lyse, resulting in fever and severe anemia Red blood cell Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Cilliates (纖毛蟲) – Use cilia to move and feed Cilia looks like a string of beads Macronucleus Figure 16. 21 C LM 60 performs the daily functions of the cell and micronuclei involved in reproduction A ciliate: Stentor Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

16. 22 Stramenopiles (髮鞭藻門) are named for their “hairy” flagella and include the water molds, diatoms, and brown algae Greek stramen, straw pilos, hair • Water molds are not fungus, although they were originally classified as fungus. • They decompose dead plants and animals (like fungus) and can be parasitic to fish. Figure 16. 22 A Downy mildew is a plant parasite related to water molds and caused the potato blight famine in Ireland 1800 s. A water mold breaking down a dead insect Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Diatoms (矽藻) - Photosynthetic, unicellular with uniquely shaped and sculptured silica walls - food source for marine animal LM 400 Fossilized diatoms make up thick sediments of diatomaceous earth, which can be used either for filtering or as an abrasive. Figure 16. 22 B Diatoms, unicellular algae Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Brown algae, large complex seaweeds - the largest algae - all are multicellular, and the brown color is due to pigments in the chloroplast Brown algae (along with red and green algae) are commonly referred to as seaweed. Figure 16. 22 C Brown algae: a kelp “forest” Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Kelp forests are used as feeding grounds by many marine species.

16. 23 Amoebozoans have pseudopodia and include amoebas and slime molds • Amoebas cross many taxonomic groups. Here, only focus on amoebozoans. • includes free-living and parasitic amoebas, and slime molds. • All members of this group have lobe-shaped pseudopodia (單數pseudopodium). Figure 16. 23 A LM 185 Amoebas capture their prey by encasing them in their pseudopodia and engulfing them into food vacuoles Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings An amoeba ingesting a smaller protist

• A plasmodial slime mold is a yellow cytoplasmic mass with multinucleate, branched, single-celled plasmodium (變形體) – That forms reproductive structures under adverse conditions Figure 16. 23 B A plasmodial slime mold: Physarum Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Cellular slime molds – are amoeboid cells that feed on bacteria in rotting vegetation. – Have unicellular and multicellular stages No food with food LM 1, 000 Slug-like aggregate, multicellular 45 Figure 16. 23 C Reproductive structure 15 Amoeboid cells Stages in the life cycle of a cellular slime mold: Dictyostelium Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

16. 24 Red algae and green algae are the closest relatives of land plants See. Fig. 16. 19 Red algae – Contribute to coral reefs, most common in tropical marine waters – endosymbiosis of red algae led to the alveolates (16. 21) and stramenopiles (16. 22) Red color in red algae comes from accessory pigments that mask the green color of chlorophyll Figure 16. 24 A A red alga: an encrusted type, on a coral reef Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Green algae – May be unicellular, colonial, or multicellular – are common inhabitants of fresh water – gave rise to the land plants (see. Fig. 16. 19) Chlamydomonas (衣滴蟲屬) Figure 16. 24 B Green algae, colonial and unicellular (inset) Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings LM 80 LM 1, 200 Volvox (團藻屬) colonies

• The life cycles of many algae – Involve the alternation of haploid gametophyte and diploid sporophyte generations Mitosis Male gametophyte Spores Gametes Mitosis Meiosis Female gametophyte Fusion of gametes Sporophyte Zygote Mitosis Figure 16. 24 C Key Haploid (n) Diploid (2 n) A multicellular green alga: Ulva (sea lettuce) and its life cycle Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

16. 25 Multicellularity evolved several times in eukaryotes 1. Formation of ancestral colonies, with all cells the same. 2. Specialization and cooperation among different cells within the colony. 3. Differentiation of sexual cells from the somatic cells Gamete Sex cells Locomotor cells 1 Unicellular protist 2 3 Foodsynthesizing cells Somatic cells Early multicellular organism Later organism that Colony with specialized, interdepenproduces gametes Figure 16. 25 dent cells Copyright © 2005 A Pearson Education, Publishing as Benjamin Cummings model for. Inc. the evolution of a multicellular organism from a unicellular protist

• Multicellular life arose over a billion years ago Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ancestral eukaryote Plants Green algae Red algae Animals Choanoflagellates Fungi Cellular slime molds Amoebozoa 2 Closest algal relatives of plants Alveolates Stramenopila Amoeba s Brown algae Diatoms Water molds Ciliates Apicomplexans Dinoflagellates 1 Plasmodial slime molds The next chapter traces the evolution of plants. Euglenozoans Diplomonads Three distinct eukaryotic lineages that led to multicellular organisms: 1. One that led to brown algae. 2. One that led to fungi and animals. 3. One that led to red and green algae and plants. 3