Kingdom Protista

Chapter 18

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

Outline cont’d.

Phylum Myxomycota – The Plasmodial Slime Molds Phylum Dictyosteliomycota – The Cellular Slime Molds Phylum Oomycota – The Water Molds

Introduction

< 1 bya, organisms confined to oceans• Protected from drying out, UV radiation, and large

fluctuations in temperature• Absorbed nutrients directly from H2O

Ca. 400 mya, green algae began making transition from H2O to land• Gave rise to green plants• Coleochaete probably indirect ancestor of land plants

−Shares features with land plants: parenchyma-like cells, cell plate and phragmoplast during mitosis, 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 diverse and heterogeneous• Nutrition varied: photosynthetic, ingestion of food,

absorption of food • Individual life cycles vary considerably• Reproduction generally by cell division and sexual

processes

Algae 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• Have chlorophylls a and b• Store food as starch• Most have single nucleus per cell• Most reproduce both sexually

and asexually

Phylum Chlorophyta

Chlamydomonas• Common in freshwater pools• Unicellular• Pair of whip-like flagella• 2 or more vacuoles at base of flagella– Regulate H2O content of cell and remove waste

• Single, cup-shaped chloroplast with 1 or 2 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

Phylum Chlorophyta

Chlamydomonas asexual reproduction:−Nucleus divides by mitosis, and cell contents

become 2 daughter cells within cellulose wall Each develop flagella and swim away No change in chromosome number; all

cells 1n

Phylum Chlorophyta

Chlamydomonas sexual reproduction:

Phylum Chlorophyta

Ulothrix• Filamentous

with holdfast cell at one end

• Single, wide, curved, somewhat flattened chloroplast, with 1-several pyrenoids

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 by fragmentation of filament

Phylum Chlorophyta

Spirogyra (watersilk) cont’d.• Sexual reproduction by conjugation

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 and have ca. 120 flagella forming fringe at one end

• Sexual reproduction by oogamy - 1 gamete motile and other stationary and large

Phylum Chlorophyta

Oedogonium sexual reproduction

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 cont’d.• Hydrodictyon (water nets) - net-like, tubular colonies

with hexagonal or polygonal meshes

– Asexual reproduction and isogamous sexual reproduction

– Isogamous - 2 flagellated gametes

Phylum Chlorophyta

• Other green algae cont’d.– Acetabularia (mermaid’s

wineglass) - consists of single, huge cell shaped like delicate mushroom• Used in classic

experiments demonstrating influence of nucleus on form of cell

• Isogamous sexual reproduction

Phylum Chlorophyta

• Other green algae cont’d.– Volvox - colonial green

algae held together in secretion of gelatinous material, resembling hollow ball• Reproduction

asexual or sexual–Smaller daughter

colonies formed inside parent colony

Phylum Chlorophyta

Other green algae cont’d.• Ulva (sea lettuce) - multicellular seaweed with

flattened green blades and basal holdfast to anchor blades to rocks−1n and 2n blades 2n blades produce spores

developing into 1n blades 1n blades bear gametangia

- form gametes Zygotes grow into 2n

blades– 1n and 2n blades indistinguishable = isomorphic

Phylum Chromophyta Yellow-green algae

(Xanthophyceae)• Mostly freshwater, with few

marine and terrestrial species−2 flagella of motile cells

oriented in opposite directions

• Vaucheria - Oogamous, coenocytic, filamentous species

–Aplanospores formed during asexual reproduction–Sexual reproduction rare Sexual reproduction in Vaucheria

Stipitococcus, a yellow-

green algae

Phylum Chromophyta

Golden-brown algae (Chrysophyceae)• Most occur in plankton of fresh H2O−Motile cells have 2 flagella of unequal

length inserted at right angles to each other Photoreceptor on short flagellum

Phylum Chromophyta

Diatoms (Bacillariophyceae)• Unicellular• Fresh and salt H2O, particularly abundant in cold

marine habitats• Dominate algal flora on damp cliffs, tree bark or

buildings• Look like ornate, glass boxes

with lids− 95% of wall silica

• Chlorophylls a and c and fucoxanthin

• Food reserves = oil, fats or laminarin

Phylum Chromophyta

Diatoms (Bacillariophyceae) cont’d.

Phylum Chromophyta

Brown algae (Phaeophyceae)• Relatively large; none unicellular

or colonial• Most marine; majority in cold,

shallow H2O

• Many have thallus differentiated into holdfast, 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) cont’d.• Sargassum - floating

brown seaweed

• Asexual reproduction by fragmentation or autospores

Sargassum

Phylum Chromophyta

• Sexual reproduction

Brown algae (Phaeophyceae)• Fucus (Common rockweed)

Phylum Rhodophyta

Red algae• In warmer and

deeper waters than brown algae

• Most filamentous with filaments so tightly packed they appear to have flattened blades or branched segments

Phylum Rhodophyta

Red algae cont’d.• Relatively

complex life cycle involving 3 types of thallus structures

• Nonmotile reproductive cells

Phylum Rhodophyta

Red algae cont’d.• Colors mostly due to phycobilins

−Similar to those of cyanobacteria Red algae may have been derived from

cyanobacteria

• Chlorophylls a, c, and sometimes d

• Food reserve - Floridean starch

• Numbers of species produce agar

Phylum Euglenophyta

Euglenoids• No cell wall; pellicle = plasma membrane and underlying

strips that spiral around cell• Flagellum• Gullet ingests food• Ca. 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

Dinoflagellates• Red tides - sudden

multiplication of dinoflagellates−Some produce

neurotoxins that accumulate in shell fish

• Cellulose “armor plates” inside cell membrane

• 2 flagella in intersecting grooves−One acts as rudder−Other gives cell

spinning motion

Phylum Dinophyta

Dinoflagellates cont’d.• Most have disc-shaped chloroplasts

−Contain xanthophyll pigments−Chlorophylls a and c

• Ca. 45% non-photosynthetic• Chromosomes remain condensed and visible

throughout life of cell• Food reserve = starch• Many have tiny projectiles that fire when irritated

Phylum Cryptophyta

• Cryptomonads• Marine and freshwater • 2 flagella• Plates on inside of plasma

membrane• Single, 2-lobed chloroplast

with starch granules surrounding central pyrenoid

• Nucleomorph - estigial nucleus of primitive symbiotic organism

• Gullet with ejectosomes - aid in propulsion• Sexual reproduction unknown

Phylum Prymnesiophyta (Haptophyta)

Haptophytes• Fresh and saltwater; major component of marine

plankton• Most unicellular, with 2 smooth flagella of similar

length inserted at apex• Pigments and food reserve similar to Chromophyta• Haptonema – 3rd flagellum located between 2 flagella

−Aids in food capture• Often covered in scales• 2 disc-shaped chloroplasts

Phylum Charophyta

Stoneworts• Shallow, freshwater lakes

and ponds• Often precipitate Ca salts on

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 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 H2O behavior

Controls development of ice crystals

Regulates penetration of water

Stabilizes suspensionsVessel 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

Plasmodial slime molds• Without chlorophyll

−Feed on bacteria and other organic particles• Consist of plasmodium– Protoplasm containing

many 2n nuclei– No cell wall– Flows rapidly and

rhythmically– Found on damp forest

debris, under logs, on dead organic material

Plasmodium

Phylum Myxomycota

Plasmodial slime molds cont’d.• Sexual reproduction:

−Plasmodium converts into separate small sporangia containing spores

Sporangia from various plasmodial slime molds

Phylum Myxomycota

• Sexual reproduction of plasmodial slime mold:

Plasmodial slime molds cont’d.

Phylum Dictyosteliomycota

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

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 not divided into individual cells

and may form large thread masses (mycelia)• Share features with brown algae, including oogamy,

cellulose in cell walls, predominantly 2n lifecycle, and zoospores with 2 flagella

• Asexual reproduction:−Crosswalls form at tips of hyphae−Zoospores produced inside and emerge through

pore

Phylum Oomycota

Water molds cont’d.• Sexual reproduction:

−Meiosis takes place in oogonia and antheridia

−Zygotes formed in oogonia give rise to new mycelia

• Human and ecological significance of water molds:−Downy mildew on

grapes−Potato blight

Review

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

Review cont’d.

Phylum Myxomycota – The Plasmodial Slime Molds Phylum Dictyosteliomycota – The Cellular Slime Molds Phylum Oomycota – The Water Molds