Features of Kingdom Protista All members have eukaryotic cells. Individual life cycles vary considerably, but reproduction is generally by cell division and sexual processes. Most multicellular members produce some motile cells.

Outline Phylum Chlorophyta Phylum Chromophyta Phylum Rhodophyta Phylum Euglenophyta Phylum Dinophyta Phylum Cryptophyta Phylum Prymnesiophyta Phylum Charophyta Phylum Myxomycota Phylum Dictyosteliomycota Phylum Oomycota

Phylum Chlorophyta The Green Algae  Includes about 7,500 species that occur in a rich variety of forms and occur in diverse, widespread habitats. - Greatest variety found in freshwater lakes, ponds, and streams. - Most have a single nucleus. - Most reproduce both sexually and asexually.

Fig. 18.2

Green Algae: contain pigments (chl a & b) similar to higher plants. store food in the form of starch within their chloroplasts.

Phylum Chlorophyta Chlamydomonas  Common inhabitant of freshwater pools.  Pair of whip-like flagella on one end pull the cell through the water.  Single, cup-shaped chloroplast with one or two pyrenoids inside. - Pyrenoids = Proteinaceous structures thought to contain starch synthesis enzymes.

Chlamydomonas

Asexual Reproduction  Nucleus divides by mitosis, and cell contents become two daughter cells within the cellulose wall. - Develop flagella and swim away.

Sexual Life Cycle of Chlamydomonas

Phylum Chlorophyta Ulothrix  Thread-like alga. - Single row of cylindrical cells forming a filament.  Basal cell functions as a holdfast.

Ulothrix Life Cycle

Phylum Chlorophyta Spirogyra (Watersilk)  Common freshwater algae consisting of unbranched filaments of cylindrical cells. - Frequently float in masses at the surface of quiet waters.  Asexual Reproduction - Fragmentation of existing filaments.  Sexual Reproduction - Papillae fuse and form conjugation tubes.

Spirogyra Sexual Reproduction

Phylum Chlorophyta Oedogonium  Epiphytic filamentous green alga. - Each cell contains a large, netlike chloroplast that rolls and forms a tube around and toward the periphery of each protoplast.

Phylum Chlorophyta Other Green Algae  Chorella - Widespread green alga composed of tiny spherical cells. - Reproduce by forming either daughter cells or autospores through mitosis.  Desmids - Mostly free-floating and unicellular. - Reproduce by conjugation.

Fig. 18.8

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.  Volvox - Colonial green algae held together in a secretion of gelatinous material - Reproduction asexual or sexual.

Fig. 18.9

Fig

Phylum Chlorophyta Other Green Algae  Ulva (Sea Lettuce) - Multicellular seaweed with flattened green blades. - Isomorphic reproductive structures.  Cladophora - Branched, filamentous green alga with species represented in both fresh and marine waters. - Mostly multinucleate.

Fig

Phylum Chromophyta The Diatoms (Bacillariophyceae)  Among best known and economically most important members of this phylum. - Mostly unicellular  Occur in both fresh and salt water.  Particularly abundant in colder marine habitats.

Fig

Reproduction in Diatoms

Phylum Chromophyta The Brown Algae (Phaeophyceae)  Relatively Large  Most Marine  Non-Unicellular or Colonial  Many have a thallus differentiated into a holdfast, a stipe, and blades. - Blades may have gas-filled bladders.  Sargassum - Floating Brown Seaweed  Fucus - Common Rockweed

Brown Alga Nereocystis

Fig

Fig

Phylum Rhodophyta The Red Algae  Most species are seaweed. - Tend to occur in warmer and deeper waters than brown algae.  Most are filamentous.  Relatively complex life cycle involving three types of thallus structures.  Colors mostly due to phycobilins.  Numbers of species produce agar.

Fig

Phylum Euglenophyta The Euglenoids  Spindle-shaped.  No cell wall, thus changes shape as it moves. - Sub-membrane strips and membrane form pellicle.  Contains gullet.  Contains red eyespot.  Reproduction by cell division.

Fig

Phylum Dinophyta The Dinoflagellates  Unicellular  Contain two flagella. - One trails behind the cell. - Other encircles the cell at right angles.  Most have disc-shaped chloroplasts. - Contain xanthophyll pigments.  Many have tiny projectiles.  Many types of toxins produced. (Red Tides)

Dinoflagellates

Human and Ecological Relevance of Algae Diatoms  Oils are sources of vitamins.  Diatomaceous Earth - Filtration - Polishes - Reflectorized Paint Other Algae  Chlorella - Potential human food source.

Human and Ecological Relevance Algae Algin  Produced by giant kelp. - Ice Cream, Salad Dressing - Latex Paint, Textiles, Ceramics Agar  Produced by red alga Gelidium. - Solidifier of nutrient culture media for growth of bacteria.

Table 18.2

Phylum Myxomycota The Plasmodial Slime Molds  Totally without chlorophyll and are incapable of producing their own food. - Distinctly animal-like during much of life cycle, but fungus-like during reproduction.  Plasmodium converts into separate small sporangia (each containing spores) during times of significant environmental changes.

Fig

Fig

Phylum Dictyosteliomycota The Cellular Slime Molds  About two dozen species of cellular slime molds are not closely related to the other slime molds. - Individual amoebalike cells feed independently, dividing and producing separate new cells periodically.  Human and Ecological Relevance - Break down organic particles to simpler substances.

Fig

Phylum Oomycota The Water Molds  Often found on dead insects.  Range in form from single spherical cells to branching, threadlike, coenocytic hyphae. - Coenocytic hyphae may form large thread masses (mycelia).