KINGDOM PROTISTA

I. Kingdom Protista

A. Heterogeneous assemblage of unicellular, colonial and multicellular Eukaryotes that do not have the distinctive characters of plants, animals or fungi

B. Contains a number of organisms previously classified as plants, animals or fungi. E.g. protozoans, all the algae except blue-greens, and several organisms previously called fungi

C. Flagella - most often involved in locomotion

1. Whiplash - without appendages

2. Tinsel - has appendages (barbs)

3. Vary in number, size and/or position, e.g. anterior, posterior, lateral. Flagella may be present only in reproductive cells or not at all

D. Sexual reproduction:

1. Isogamy - motile gametes the same size

2. Anisogamy - motile gametes with the female larger than the male

3. Oogamy - large non-motile female, smaller motile male

II. Classification

A. Our text recognizes 12 divisions. See tables in your text for a summary of their major characteristics

B. Classification based on modes of nutrition, pigments (if present), carbohydrate food reserves, flagella, cell wall components and the environments they inhabit

III. Importance

A. Important components of food chains. E.g. kelp beds are among the most productive ecosystems on earth

B. Unicellular aquatic Protista (plankton) form a very important component of the food chain. The photosynthetic ones are called phytoplankton and the heterotrophic ones are called zooplankton (which also includes many animal larvae or tiny crustaceans)

PHYLA OF PROTISTA

I. Euglenophyta - euglenoids - Named for Euglena

A. Mostly freshwater

B. About 900 species

C. Virtually all are unicellular except for one colonial genus

D. About 1/3 of the genera contain chloroplasts with chlorophylls A & B and carotenoids as found in true plants

E. Appears they are derived from protozoa by incorporation of chloroplasts. If grown under proper conditions cells may replicate faster than the chloroplasts, giving rise to non-photosynthetic cells which are nearly indistinguishable from protozoa. The heterotrophs ingest food

F. Paramylon carbohydrate food reserve (a polysaccharide glucan with 1-3 linkage)

G. Instead of a cell wall they have a pellicle, a flexible layer of interlocking proteinaceous strips inside plasma membrane

H. Reproduction via simple cell division. Sexual reproduction is lacking

II. Myxomycota - Commonly called plasmodial slime molds. 

A. About 700 species

B. Terrestrial

C. Heterotrophic

D. Glycogen carbohydrate food reserve

E. Diploid

F. Lack cell walls - exist as streaming masses of naked protoplasm which "creeps" over lawns, plants, rotting materials. They can cover an area of several meters

1. Plasmodium - masse of naked protoplasm. As they travel they engulf bacteria, yeast cells, fungal spores and decayed plant and animal matter. The plasmodium contains many nuclei which undergo synchronous divisions

G. Sexual reproduction involves the fusion of amoebae and/or flagellated gametes which come from spores produced within sporangia

H. The life cycle of Physarum is on p. 353 of your text

III. Rhodophyta - commonly called red algae

A. About 4,000 - 6,000 species

B. Mostly marine but a few freshwater species, particularly abundant in tropical and warm regions.

C. Usually grow attached to rocks or other algae, but there are a few free floating forms and a few unicellular or colonial forms

D. No flagellated cells at all in life cycle

E. They lack centrioles and structures called polar rings play the role of centrioles

F. Autotrophic - contain only chlorophyll A, plus carotenoids, phycobilins

1. Their chloroplasts seem to have originated as symbiotic cyanobacteria, which they resemble both biochemically and structurally

G. Floridean starch carbohydrate food reserve

1. Floridean starch is more glycogen like (found in animals and fungi) than other plant starches

H. Cell walls of cellulose or other polysaccharides, plus gelatinous pectic materials, e.g. agar and carrageenan (sulfated polymers of galactose)

1. Agar is used to make gelatinous capsules for pills, cosmetic base, culture medium for microbiology, rapid setting jellies and desserts

2. Carrageenan is a stabilizer in emulsions such as paints, cosmetics, and dairy products

I. Some species deposit calcium carbonate in their cell walls, called coralline algae. They play an important role in building coral reefs. They, along with dinoflagellates provide the food for the coral

J. Growth forms include simple filamentous as well as more complex three-dimensional forms composed of densely interwoven filaments held together by the gelatinous matrix

IV. Oomycota - Commonly called water molds. Also includes downy mildews, potato blight and many important agricultural pests on a variety of crops

A. About 700 species

B. Unicellular to highly branched, coenocytic, filamentous forms

C. Heterotrophic

D. Cellulose cell walls

E. Glycogen carbohydrate food reserve

F. Both sexual and asexual reproduction

1. Sexual reproduction involves an oogonium which contains many eggs and an antheridium which contains many male nuclei. Syngamy results in formation of thick walled zygote called an oospore

2. Asexual reproduction is via zoospores

G. Saprolegnia is the common water mold, see your text for its life cycle

V. Bacillariophyta - diatoms

A. About 100,000 extant species and many thousands of extinct species

B. Major component of aquatic ecosystems. May account for 25% of the total primary production on earth

C. Mostly unicellular but a few colonials

D. Diploid

E. Most autotrophic, a few are heterotrophic

1. Autotrophs contain chlorophylls A & C and fucoxanthin, a golden-brown carotenoid. Some have lost their shells and they live symbiotically inside marine protozoa

F. Chrysolaminarin (a glucose-mannitol polymer) carbohydrate food reserve ( similar to the laminarin found in the brown algae)

G. Lack flagella

H. Cell walls, called frustules, are polymerized, opaline silica (glass like)

1. The two halves of the frustules fit together like a Petrie dish

I. Reproduction mainly asexual. The two halves of the frustules open and each side generates a new half. Sexual reproduction takes place via oogamy

J. Diatoms are abundant in the fossil record from at least 250 million years ago. Their silica shells have accumulated in large numbers to form large deposits of diatomaceous earth. Diatomaceous earth is used as filtering agents, insulating materials, abrasives (toothpaste, silver polish). One cubic cm contains 4.6 million diatom shells

K. See your text for a typical diatom life cycle

VI. Phaeophyta - commonly called brown algae and/or kelps

A. About 1,500 species

B. Includes most of the conspicuous seaweeds of temperate regions, particularly along shorelines and intertidal zones

1. Kelp beds are some of the most productive ecosystems on earth. They flourish to depths of 100 ft., and may extend out about 6 miles from the coast line. The free floating forms may form dense masses, e.g. Sargassum forms the Sargasso Sea in the Atlantic northeast of the Caribbean Islands. Sizes range from microscopic to giant kelps up to 200 ft. long.

C. Almost entirely marine, primarily of colder oceans

D. Some of the kelps have tissue differentiation into holdfast, stipe and blade. Some also have air bladders for flotation

E. Some have conducting tissue in the stipe for food transport from photosynthetic blades way down into dark areas below sunlight penetration. There is also lateral translocation from outer photosynthetic layers to inner layers. Mannitol and amino acids are primary material that is translocated

F. Contain chlorophyll A & C, carotenoids, and fucoxanthin (same as Bacillariophyta)

G. Carbohydrate food reserve is laminarin (glucose-mannitol polymer) which is similar to the chrysolaminarin [more polymerized form of laminarin] of the Bacillariophyta

H. Only reproductive cells have flagella

I. Cell walls are a matrix of cellulose and alginic acids (polysaccharides)

1. Algin is a mucilaginous intercellular material used as a stabilizer and emulsifier for foods and paints, and coating for paper

J. See your text for the life cycle of  Fucus, a common tide pool alga of the California coast

VII. Chlorophyta - commonly called green algae

A. About 17,000 species

B. This is the group which gave rise to the true plants

C. Very diverse division with a wide variety of life forms and life histories

D. Most  are multicellular, but there are a few unicellular forms. Many growth forms:

1. Unicellular motile - Chlamydomonas is typical flagellated, unicellular type. It has one large chloroplast and reproduces asexually via successive mitoses or sexually by fusion of two cells. Chlamydomonas life cycle

2. Unicellular non-motile  - look much like Chlamydomonas but lack flagella

3. Non-motile colonial  - free floating colonies, e.g. the water net, Hydrodictyon

4. Motile colonial - two to thousands of Chlamydomonas - like cells held together in a gelatinous matrix. E.g. Volvox is a spectacular spherical colonial form made up of up to 60,000 Chlamydomonas like cells. The flagella of each cell beat in synchrony to move the colony about. There appears to be some division of labor and therefore beginnings of multicellularity & differentiation 

5. Filamentous - E.g. Ulothrix and Spirogyra

6. Siphonous - very large, coenocytic "cells" such as Acetabularia

7. Multicellular - E. g. Ulva, the sea lettuce. Some may be highly branched and differentiated. Fritschella is a terrestrial multicellular form which has underground rhizoids, a prostrate stem and erect branches. Chara is the most complex green alga. It has nodes and internodes, whorls of branches, and eggs contained in very complex structure

E. Mostly freshwater but some marine and terrestrial species found on soil, tree trunks, surface of snow, and as symbionts with fungi in Lichens

F. Have chlorophylls A & B and carotenoids, just like true plants

G. Starch carbohydrate food reserve and it is stored inside the plastids, just like true plants

H. Cell walls are composed of cellulose and some species also contain a matrix of hemicellulose and pectic materials, just like true plants

I. Classification: two types of green algae characterized by different types of cell division:

1. Phragmoplast line - Nuclear envelope disintegrates at the start of mitosis and the spindle persists after the chromosomes separate. A series of microtubles, the phragmoplast, forms perpendicular to the plane of cell division. The spindle remains until it is broken by either a cell plate or by furrowing. True plants have a phragmoplast and the nuclear envelope disappears. This line of the green algae gave rise to true plants

2. Phycoplast line - Nuclear envelope persists through mitosis and the non-persistent spindle collapses after the chromosomes separate. A new system of microtubles, the phycoplast, develops parallel to the plane of cell division. This ensures that the cleavage furrow passes between the two daughter nuclei

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