General Characteristics

of ALGAE

Algae are eukaryotic organisms that have no roots, stems, or leaves but do have chlorophyll and other pigments for

carrying out photosynthesis. Algae can be multicellular or

unicellular.

Algae is classified into six main divisions: Chlorophyta: Green Algae, Rhodophyta: Red algae, Phaeophyceae: Brown Algae, Pyrrophyta:Dinoflagellates, Bacillariophyta: Diatoms,

Euglenophyta: Euglenoids, and Chrysophyta: golden-brown algae.

Here are the characteristics of each of these types of algae.

Chlorophyta: Green AlgaeCharacteristics: Green

colour from chlorophyll a and b in the same proportions as the 'higher' plants; beta-carotene (a yellow pigment); and various characteristic xanthophylls (yellowish or brownish pigments). Food reserves are starch, some fats or oils like higher plants. Green algae are thought to have the progenitors of the higher green plants but there is currently some debate on this point.

Live in both fresh and salt water.Many exist as long filaments, or strings.Produce most of the oxygen we breath.Some species pollute public water systems by

poisoning the water and producing a foul smell.

Rhodophyta: Red algaeCharacteristics: The red colour of

these algae results from the pigments phycoerythrin and phycocyanin; this masks the other pigments, Chlorophyll a (no Chlorophyll b), beta-carotene and a number of unique xanthophylls. The main reserves are typically floridean starch, and floridoside; true starch like that of higher plants and green algae is absent. The walls are made of cellulose and agars and carrageenans, both long-chained polysaccharide in widespread commercial use. There are some unicellular representatives of diverse origin; more complex thalli are built up of filaments.

Live only in salt water.Color results from combination of blue, red,

and green pigments.Used as food.Produce carrageen, a thickener used in ice

cream and pudding.

Phaeophyceae: Brown Algae The brown colour of these algae

results from the dominance of the xanthophyll pigment fucoxanthin, which masks the other pigments, Chlorophyll a and c (there is no Chlorophyll b), beta-carotene and other xanthophylls. Food reserves are typically complex polysaccharides, sugars and higher alcohols. The principal carbohydrate reserve is laminaran, and true starch is absent (compare with the green algae). The walls are made of cellulose and alginic acid, a long-chained heteropolysaccharide.

Live only in salt water.Color results from combination of green and

brown pigments.Represent the largest species of algae.Used as food.Produce algin, a gummy substance used in

making cosmetics and ice cream.

Pyrrophyta:DinoflagellatesLive only in salt

water.Have two flagella:

one for locomotion and one for steering.

Often appear red.Some release toxins

into the water, causing a "red tide" that often kills large numbers of fish and other marine life.

Euglenophyta: EuglenoidsThe Euglenophyta or

euglenoids are 800 species of unicellular, protozoan-like algae, most of which occur in fresh waters. The euglenoids lack a true cell wall, and are bounded by a proteinaceous cell covering known as a pellicle.

Euglenophytes have one to three flagellae for locomotion, and they store carbohydrate reserves as paramylon. The primary photosynthetic pigments of euglenophytes are chlorophylls a and b, while their accessory pigments are carotenoids and xanthophylls.

Most euglenoids have chloroplasts, and are photosynthetic. Some species, however, are heterotrophic, and feed on organic material suspended in the water. Even the photosynthetic species, however, are capable of surviving for some time if kept in the dark, as long as they are "fed" with suitable organic materials.

Chrysophyta: golden-brown algaeThe Chrysophyta are the

golden-brown algae and diatoms, which respectively account for 1,100 and 40,000-100,000 species of unicellular algae. These algae occur in both marine and fresh waters, although most species are marine. The cell walls of golden-brown algae and diatoms are made of cellulose and pectic materials, a type of hemicellulose.

Live in both fresh and salt water.Have glassy cell walls, which form a two-part

shell that fits together like two halves of a Petri dish.

Form the base of the marine food chain.Large deposits of diatomaceous earth found

in many places were formed from the remains of diatoms.

Used to make cleansers, pool filters, and toothpaste.

BacillariophytaIt is unicellularProdominant color:

Olive BrownLives only on

Freshwater and seawater.