AlgaeDavid Fan

I. AlgaeA. Characteristics

1. Algae are all photosynthetic (autotrophy) organisms that aren’t plants or animals

2. Plant-like protists3. Unicellular or multicellular, eukaryotic, motile or nonmotile4. Unlike plants, algae lack roots, leaves and flowers5. Major types: chrysophytes, diatoms, dinoflagellates, red algae,

brown algae, and green algae.

B. Classification1. Divided into seven main divisions for convenience, not

evolutional or biological significance: Chrysophyta, Pyrrophyta, Euglenophyta, Chlorophyta, Rhodophyta, Phaeophyta, and Xanthophyta.

2. Classification is based on the combination of photosynthetic pigments contained in the plastids, the cellular structure and organization, composition of the cell wall, the presence or absence of flagella, reproductive means, and motility

C. Chysophyta (Golden Algae)1. Diatoms2. Contain the photosynthetic pigments chlorophyll c and

carotenoids such as fucoxanthin that give them a yellowish brown color in addition to the chlorophyll a that is common to all algae.

3. Unicellular; motile. Some are non-motile4. Cell walls contain silicon compounds, pectin and cellulose5. In absence of light or food, chrysophytes can become

falculatively heterotrophic; they feed on diatoms and bacteria6. Closely related to diatoms7. Store food reserves as oil droplets giving buoyancy to position

closely to sun to store energy8. Usually reproduce asexually, sexually only when needed

D. Pyrrophyta (Fire Algae)1. Dinoflagellates

1. Unicellular2. Chlorophyll C3. Photosynthetic4. Closely resemble ciliated protists5. Perpendicularly arranged flagella, one at the posterior end

and another located within a groove and that spins as the cell swims.

6. Like diatoms, they store energy as oil droplets, also starch

7. Some are motile; free swimming. Some are non-motile; live in symbiotic relationships

a. Many coral have dinoflagellates living in them8. Tend to form algal blooms9. Salt and freshwater10. Reproduce asexually

E. Euglenophyta1. Third strictly unicellular division of algae2. Chlorophylls A, B and carotenoids3. Live in freshwater4. Flagella5. Light sensitive eyespot that searches for environment conducive

to photosynthesis6. Multiple chloroplasts7. Store food as starch

F. Chlorophyta (Green Algae)1. Most diverse and well known group of algae2. Like all plants, they have Chlorophyll A, B and carotenoids3. Mostly unicellular, freshwater4. Some are multicellular, saltwater5. Some live in terrestrial environments6. Filamentous algae forms green mat that coats top of lakes

F. Rhydophyta (Red Algae)1. Marine2. Mostly multicellular3. Contain phycobilins, photosynthetic pigments that capture green

and blue light that penetrates deep into the water. Helps them survive at deep depths

4. Some have cell walls made of calcium carbonate; help build coral reefs

5. Reproduce asexually and sexually (meiosis)G. Phaeophyta (Brown Algae)

1. Chlorophylls A and C and fucoxanthin2. Have structures similar to plants3. Mostly live in saltwater, 4 species live in freshwater 4. Attach to rocks near water or float near surface of water5. Gas-filled floats keep blades closer to sunlight6. Mostly multicelllar7. Brown and red algae together constitute seaweed

H. Xanthophyta (Yellow-Green Algae)1. Primarily inhabit freshwater2. No chlorophyll B or fucoxanthin3. Have Chlorophyll C4. Mostly unicellular, and have flagella5. Some are colonial (live in group, not motile

I. Reproduction1. Some reproduce asexually by mitosis2. Others reproduce by fragmentation or spore formation

1. Flagellated spores are common to aquatic algae2. Nonmotile spores are common to terrestrial algae

3. Some reproduce sexally by meosisJ. Ecological Importance

1. As primary producers, algae play a vital niche in many ecosystems

2. They play a vital part in aquatic food webs, produce most of he world’s oxygen and provide iodine and protein for humans

3. However, when algae are given too many favorable conditions, they can over reproduce and cause algae blooms

K. Economic Importance1. Many East Asian cultures eat red and green algae (seaweed)2. Carrageen is used to improve texture in products3. Other extracts are used in products