Upload
oliver-alexander-todd
View
214
Download
1
Embed Size (px)
Citation preview
Chapter 15
Lecture Outline
Kingdom Protista
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Outline Introduction Features of Kingdom Protista Algae Phylum Chlorophyta – The Green Algae Phylum Chromophyta – The Yellow-Green Algae, Golden-Brown
Algae, Diatoms, and Brown Algae Phylum Rhodophyta – The Red Algae Phylum Euglenophyta – The Euglenoids Phylum Dinophyta – The Dinoflagellates Phylum Cryptophyta – The Cryptomonads Phylum Prymnesiophyta (Haptophyta) – The Haptophytes Phylum Charophyta – The Stoneworts Human and Ecological Relevance of the Algae Phylum Myxomycota – The Plasmodial Slime Molds Phylum Dictyosteliomycota – The Cellular Slime Molds Phylum Oomycota – The Water Molds
Introduction Less than 1 billion years ago, organisms
confined to oceans.• Protected from drying out, ultraviolet radiation, and
large fluctuations in temperature• Absorbed nutrients directly from water
About 400 million years ago, green algae began making transition from water to land.• Gave rise to green plants
– Coleochaete probably indirect ancestor of land plants.o Shares features with land plants: cells
that resemble parenchyma, development of cell plate and phragmoplast during mitosis, a protective covering for zygote, and production of lignin-like compound
Coleochaete
Features of Kingdom Protista Domain Eukarya - All members have eukaryotic cells.
• Includes Kingdoms: Protista, Plantae, Fungi, Animalia
Organisms in Protista vary from unicellular to multicellular.
• Nutrition varied: photosynthetic, ingestion of food, absorption of food
• Individual life cycles vary considerably.
• Reproduction generally by cell division and sexual processes.
Algae are in Kingdom Protista.
• Grouped into several phyla based on form of reproductive cells, and combinations of pigments and food reserves.
Phylum Chlorophyta Green algae
• Unicellular, filamentous, platelike colonies, netlike tubes, hollow spheres, lettuce-like leaves
• Greatest variety in freshwater lakes, ponds, and streams– Some on tree bark, in animal
fur, in snowbanks, in flatworms or sponges, on rocks, in lichen “partnerships.”
• Have chlorophylls a and b
• Store food as starch
• Most have a single nucleus per cell.
• Most reproduce both sexually and asexually.
Phylum Chlorophyta Chlamydomonas
• Common inhabitant of freshwater pools
• Unicellular
• Pair of whip-like flagella on one end pull cell through water.• Two or more vacuoles at base of
flagella– Regulate water content of cell and
remove waste
• Single, cup-shaped chloroplast with one or two pyrenoids inside– Pyrenoids - Proteinaceous
structures associated with synthesis of starch
• Red eyespot near base of flagella – Allows alga to swim toward light
Phylum Chlorophyta Chlamydomonas
• Asexual reproduction:– Nucleus divides by mitosis, and cell contents become
two daughter cells within cellulose wall.o Each develop flagella and swim away.o No change in chromosome number; all cells remain
haploid.
Phylum Chlorophyta Chlamydomonas sexual reproduction:
• Meiosis occurs in zygospore, producing 4 haploid zoospores that grow into full-sized algae.
• Under certain conditions, cells congregate together.
• Two cells fuse together to form zygote, that will become zygospore and may remain dormant.
Phylum Chlorophyta Ulothrix
• Filamentous with holdfast cell at one end
• Chloroplast - Wide, curved, somewhat flattened, with one to several pyrenoids
• Asexual reproduction:– Cells contents condense, divide by mitosis and become
zoospores inside parent cell.
– Zoospores escape through pore in parent cell wall.o Resemble Chlamydomonas cellso Grow into new filaments
Phylum Chlorophyta
• Cell contents condense and divide by mitosis inside parent cell.
• Each new cell produces flagella.
• Cells escape from parent cell and become gametes.
Ulothrix sexual reproduction:
Phylum Chlorophyta Spirogyra (watersilk)
• Filaments of cylindrical cells
• Frequently floats in masses on surface of quiet freshwater
• Chloroplast ribbon-shaped and spirally wrapped around vacuole, with pyrenoids at regular intervals.
• Asexual reproduction:– Only by fragmentation of
filament
Phylum Chlorophyta Spirogyra (watersilk)
• Sexual reproduction by conjugation.– Papillae fuse and form conjugation tubes.– Condensed protoplast of one filament flows or crawls through
tube to adjacent cell.– Protoplasts fuse, forming zygote that develops thick wall.– Eventually zygote undergoes meiosis.
Phylum Chlorophyta Oedogonium
• Epiphytic filamentous green alga with holdfast
• Large netlike chloroplast with pyrenoids at intersections of net
• Asexual reproduction:– By fragmentation or by zoospores
– Zoospores produced singly in cells at tips of filaments.o Have about 120 flagella that form fringe toward one
end of zoospore
Phylum Chlorophyta Oedogonium sexual
reproduction:• Exhibits oogamy - One
gamete is motile, while other is larger and stationary. – Antheridium - Boxlike cell that
produces two motile sperm– Oogonium - Swollen cell
containing single egg
• Sperm enters oogonium through pore.
• Zygote forms thick walls and may remain dormant.
• Zygote produces 4 zoospores by meiosis that grow into new haploid filaments.
Phylum Chlorophyta Other green algae
• Chlorella - Widespread green alga composed of tiny spherical cells– Only reproduce asexually by forming either daughter cells
or autospores through mitosis
– Used in research; may become important as food source
• Desmids - Mostly free-floating and unicellular– Reproduce by conjugation
Closterium, a desmid
Phylum Chlorophyta Other green algae
• Hydrodictyon (water nets) - Net-like, tubular colonies with hexagonal or polygonal meshes– Asexual
reproduction, as well as isogamous sexual reproduction
– Isogamous = two flagellated gametes
Phylum Chlorophyta Other green algae
• Acetabularia (mermaid’s wineglass) - Consists of a single, huge cell shaped like a delicate mushroom– Used in classic
experiments demonstrating influence of nucleus on form of cell
– Isogamous
Phylum Chlorophyta Other green algae
• Volvox - Colonial green algae held together in a secretion of gelatinous material, resembling hollow ball– Reproduction asexual
or sexualo Smaller daughter
colonies formed inside parent colony
Phylum Chlorophyta Other green algae
• Ulva (sea lettuce) - Multicellular seaweed with flattened green blades and basal holdfast to anchor blades to rocks– Haploid and diploid blades
o Diploid blades produce spores that develop into haploid blades.
o Haploid blades bear gametangia that form gametes.
o Gametes fuse to form zygotes that grow into diploid blades.
– Exhibit isomorphism - Haploid and diploid blades indistinguishable.
Phylum Chromophyta Yellow-green algae
(Xanthophyceae)
• Mostly freshwater, with a few marine and terrestrial representatives– Two flagella of motile cells are
oriented in opposite directions.
– Vaucheria - Oogamous, coenocytic, filamentous specieso Aplanospores formed during
asexual reproduction.o Sexual reproduction rare.
Sexual reproduction in Vaucheria
Stipitococcus, a yellow-green
algae
Phylum Chromophyta Golden-brown algae (Chrysophyceae)
• Most occur in the plankton of fresh water.– Motile cells have two flagella of unequal length inserted
at right angles to each other.o Photoreceptor on short flagellum.
Phylum Chromophyta The Diatoms (Bacillariophyceae)
• Unicellular
• Fresh and salt water, particularly abundant in cold marine habitats
• Also, dominate algal flora on damp cliffs, tree bark or buildings
• Look like ornate, glass boxes with lids– As much as 95% of wall is silica.
• Chlorophylls a and c and fucoxanthin
• Food reserves - Oil, fats or laminarin
Phylum Chromophyta The Diatoms (Bacillariophyceae)
• Asexual reproduction results in half of cells becoming progressively smaller.
• Original cell size restored through sexual reproduction.
Phylum Chromophyta Brown algae (Phaeophyceae)
• Relatively large; none unicellular or colonial
• Most marine; majority in cold, shallow water, except giant kelp
• Many have a thallus differentiated into a holdfast, a stipe, and blades.– Blades may have gas-filled
bladders.
• Chlorophylls a and c, fucoxanthin
• Food reserve = laminarin
• Algin in cell walls. Nereocystis, a kelp
Phylum Chromophyta Brown algae
(Phaeophyceae)
• Sargassum - Floating brown seaweed
• Asexual reproduction by fragmentation or autospores.
Sargassum
Phylum Chromophyta
– Sexual reproduction:o Receptacles at tips of
branches contain spherical chambers called conceptacles with gametangia inside.« Oogonium produces
8 eggs.« Antheridium
produces 64 sperm.o Eggs and sperm
released into water.
Brown algae (Phaeophyceae)• Fucus - Common rockweed
Phylum Rhodophyta The red algae
• In warmer and deeper waters than brown algae
• Most are filamentous with filaments so tightly packed they appear to have flattened blades or branched segments.
Phylum Rhodophyta The red algae
• Relatively complex life cycle involving three types of thallus structures
• Nonmotile reproductive cells
Phylum Rhodophyta The red algae
• Colors mostly due to phycobilins.– Similar to those of cyanobacteria
o Red algae may have been derived from cyanobacteria.
• Chlorophylls a, and sometimes d
• Food reserve - Floridean starch
• Numbers of species produce agar.
Phylum Euglenophyta The Euglenoids
• No cell wall; pellicle = plasma membrane and underlying strips that spiral around cell
• Flagellum pulls cell through water.
• Gullet ingests food.
• About 1/3 of species have disc-shaped chloroplasts.
• Red eyespot for light detection
• Paramylon food reserve
• Asexual reproduction by cell division.
• Sexual reproduction not confirmed.
Phylum Dinophyta The Dinoflagellates
• Red tides - Sudden multiplication of dinoflagellates– Some produce neurotoxins
that accumulate in shell fish.
• Cellulose “armor plates” inside cell membrane
• Two flagella in intersecting grooves– One trails behind cell - Acts
as rudder
– Other encircles cell at right angles - Gives cell spinning motion
Phylum Dinophyta The Dinoflagellates
• Most have disc-shaped chloroplasts.– Contain xanthophyll pigments
– Chlorophylls a and c
• About 45% nonphotosynthetic
• Chromosomes remain condensed and visible throughout life of cell.
• Starch food reserve
• Many have tiny projectiles that fire when irritated.
Phylum Cryptophyta The Cryptomonads
• Marine and freshwater
• Two flagella
• Plates on inside of plasma membrane
• Single, two-lobed chloroplast with starch granules surrounding a central pyrenoid
• Nucleomorph - Vestigial nucleus of primitive symbiotic organism
• Gullet lined with ejectosomes.
• Sexual reproduction unknown.
Phylum Prymnesiophyta (Haptophyta) The Haptophytes
• Fresh and saltwater; major component of marine plankton
• Most unicellular, with two smooth flagella of similar length inserted at the apex.
• Pigments and food reserve similar to Chromophyta.
• Haptonema - Third flagellum located between two flagella.– Aids in food capture
• Often covered in scales
• Two disc-shaped chloroplasts
Phylum Charophyta The Stoneworts
• Shallow, freshwater lakes and ponds
• Often precipitate calcium salts on their surfaces
• Axis with short lateral branches in whorls.
• Sexual reproduction is oogamous.
• Multicellular antheridia
Human and Ecological Relevance of Algae Protistan algal phyla at bottom of food chain.
Diatoms
• Oils are sources of vitamins.
• Diatomaceous earth– Filtration
– Polishes, toothpaste
– Paint that reflects light
Other algae
• Chlorella– Potential human food source
Human and Ecological Relevance of Algae Algin
• Produced by giant kelps and other brown algae– Ice cream, salad dressing
– Latex paint, textiles, ceramics
– Regulates water behavioro Controls development of
ice crystalso Regulates penetration
of watero Stabilizes suspensions
Vessel harvesting kelp
Human and Ecological Relevance of Algae Minerals and food
• Iodine from kelp
• Red algae– Food - Dulse, nori
– Carrageenan - Thickening agent
Agar
• Produced by red alga Gelidium– Solidifier of nutrient culture media
– Retains moistness in bakery products
– Base for cosmetics
Phylum Myxomycota The Plasmodial slime molds
• Without chlorophyll– Feed on bacteria and other organic particles
• Consist of a plasmodium– Protoplasm containing
many diploid nuclei
– No cell wall
– Flows rapidly and rhythmically
– Found on damp forest debris, under logs, on dead organic material
Plasmodium
Phylum Myxomycota The Plasmodial slime molds
• Sexual reproduction:– Plasmodium converts into separate small sporangia
that contain spores.
Sporangia from various plasmodial slime molds
Phylum Myxomycota
• Sexual reproduction: – Meiosis occurs
in spores.
– Spores grow into myxamoebae that act as gametes and fuse to form zygotes.
– Zygotes grow into new plasmodia.
The Plasmodial slime molds
Phylum Dictyosteliomycota The Cellular slime molds
• Individual amoebalike cells feed independently, dividing and producing separate new cells periodically.
• Clump together to form mass called pseudoplasmodium– Crawls like a garden slug
– Eventually transforms into sporangium-like mass of spores
Human and ecological relevance of the slime molds:
– Break down organic particles to simpler substances
Phylum Oomycota The Water molds
• Cottony growths on fish; often found on dead insects
• Range in form from single spherical cells to branching, threadlike, coenocytic hyphae
– Coenocytic hyphae are not divided into individual cells and may form large thread masses (mycelia).
• Share features with brown algae, including oogamy, cellulose in cell walls, predominantly diploid lifecycle, and zoospores with two flagella
• Asexual reproduction:
– Crosswalls form at tips of hyphae
– Zoospores produced inside and emerge through pore.
Phylum Oomycota The Water molds
• Sexual reproduction:– Meiosis takes place in
oogonia and antheridia.– Zygotes formed in
oogonia give rise to new mycelia.
• Human and ecological significance of the water molds:– Downy mildew on grapes– Potato blight
o 1846 famine in Ireland
Outline Introduction Features of Kingdom Protista Algae Phylum Chlorophyta – The Green Algae Phylum Chromophyta – The Yellow-Green Algae, Golden-Brown
Algae, Diatoms, and Brown Algae Phylum Rhodophyta – The Red Algae Phylum Euglenophyta – The Euglenoids Phylum Dinophyta – The Dinoflagellates Phylum Cryptophyta – The Cryptomonads Phylum Prymnesiophyta (Haptophyta) – The Haptophytes Phylum Charophyta – The Stoneworts Human and Ecological Relevance of the Algae Phylum Myxomycota – The Plasmodial Slime Molds Phylum Dictyosteliomycota – The Cellular Slime Molds Phylum Oomycota – The Water Molds