Those algae that move from the cytoplasm of the cell by forming rhizopods or pseudopods are called amoeboids. Like Heterochloris, Chromulina etc.

A number of stationary unicellular algae without flagella join together to form a pentagonal or hexagonal colony. This is called stationary uncovered colony. It is not covered by gelatin coating. Eg- Pediastrum, Hydrodictyon, Scenedesmu etc.

A large number of single-celled flagellated algae form a motile free colony. There is no mucilage coating outside the colony. For example – Pyrobotrys.
5. Non-motile enveloped colony algae
Some non-motile unicellular algae form colonies by being enveloped in a gelatinous membrane. This is called a stationary covered colony. For example – Microcystis, Eucapsis etc.

When a large number of unicellular flagellated algae form a colony covered by a gelatinous membrane, it is called a motile enveloped colony. A colony in which a certain number of motile cells are arranged in a certain pattern is called a synobium. Synobium algae are interconnected and their flagella are outwardly oriented. Each synobium can contain 4-50,000 algae. E.g. Eudorina, Pleodorina, Pandorina, Volvox etc.

The body of algae is made up of a single cell and is spherical or oval in shape. Cells are stationary because they do not have flagella or cilia. Such as Chlorococcum, Chlorella, Chamaesiphon, Gloeocapsa etc.

The body of algae is composed of a single cell and is round or oval or ellipsoid. Cells have a nucleus and a chloroplast. 1-2 flagella are present in front of the cell. Such as Chlamydomonas, Euglena, Phacus, Navicula etc.

Algae show the greatest diversity in organisms due to their physical structure. Algae can range from microscopic (Micromonas) to large (30-60 m) kelp.
1. Motile unicellular: The body of algae is composed of a single cell and is round or oval or ellipsoid. Cells have a nucleus and a chloroplast. 1-2 flagella are present in front of the cell. Such as Chlamydomonas, Euglena, Phacus, Navicula etc.
2. Non-motile unicellular: The body of algae is made up of a single cell and is spherical or oval in shape. Cells are stationary because they do not have flagella or cilia. Such as Chlorococcum, Chlorella, Chamaesiphon, Gloeocapsa etc.
3. Motile enveloped colony: When a large number of unicellular flagellated algae form a colony covered by a gelatinous membrane, it is called a motile enveloped colony. A colony in which a certain number of motile cells are arranged in a certain pattern is called a synobium. Synobium algae are interconnected and their flagella are outwardly oriented. Each synobium can contain 4-50,000 algae. E.g. Eudorina, Pleodorina, Pandorina, Volvox etc.
4. Motile free colony: A large number of single-celled flagellated algae form a motile free colony. There is no mucilage coating outside the colony. For example – Pyrobotrys.
5. Non-motile enveloped colony: Some non-motile unicellular algae form colonies by being enveloped in a gelatinous membrane. This is called a stationary covered colony. For example – Microcystis, Eucapsis etc.
6. Non-motile free colony: A number of stationary unicellular algae without flagella join together to form a pentagonal or hexagonal colony. This is called stationary uncovered colony. It is not covered by gelatin coating. Eg- Pediastrum, Hydrodictyon, Scenedesmu etc.
7. Amoeboid: Those algae that move from the cytoplasm of the cell by forming rhizopods or pseudopods are called amoeboids. Like Heterochloris, Chromulina etc.
8. Pamelloid: Motile algae lose their flagella and become encased in a mucilage coat and survive the hostile environment. This condition is called Pamela Dasha. Such as Chlamydomonas, Ulothrix, Sargassum, Fucus, Tetraspora, Aphanothece, Gonium etc.
9. Filamentous: If the cells of algae are joined together to form a narrow, linear, unbranched structure, it is called filamentous. Eg- Oedogonium, Ulothrix, Scytonema, Tolypothrix, Cladophora, Pithophora, Spirogyra etc.
10. Dendroid: Dendroid means tree-like. The underside of each algal cell is covered with mucilage and joins together to form colonies. Such structures are called dendroids. For example, Prasinocladus.
11. Thalloid & Leaflike: If the cells of algae divide and form a thin and flat leaf-like thallus, it is called thalloid. For example, Enteromorpha, Porphyra, Ulva etc.
12. Web like: They make web like structure. Eg- Hydrodictyon.
13. Heterotricus: The thallus of algae consists of two parts. Recumbent part and aerial part. A thallus with such features is called heterotrichous. Such as Coleochaete, Fritschiella, Stigeoclonium, Trentepohlia etc.
14. Siphonus: Algae with hollow cylindrical body are called siphon algae. These hollow tubes are called sinusites. Such as Vaucheria, Botrydium, Protosiphonia etc.
15. Polysiphonus: The body of polysiphon algae consists of many siphons or hollow cylindrical parts. Its central sinusoid is called central siphon and surrounding sinusoid is called pericentral siphon. Eg- Codium, Polysiphonia.
16. Nodas: Their body consists of Parva and Parvamadhya. Lateral branches arise from the pars. Like- Chara, Nitella etc.
17. Complex Algae Body: The body of some algae is made up of three parts. Hold fast, stipe and frond. Fronds are flat like leaves. Such a structure is called a complex body. Such as- Fucus, Laminaria, Sargassum.

(i) Red algae appear red due to the presence of r-phycoerythrin pigment. These are called marine mosses.
(ii) Red algae that form coral reefs are called coralline algae. They excrete calcium carbonate to form coral reefs.
(iii) Red algae increase the body’s immune system by producing white blood cells.
(iv) Nori in Japan, Jim in Korea and Laver in UK are made from Porphyra algae.
(v) They are a large group of marine algae with over 7000 species.
Some red algae- Corallina elongata, Bangia fuscopurpurea, Stylonema alsidii, Polysiphonia lanosa etc.

[Some blue green algae- Nostoc calcicola, Anabaena laxa, Microcystis aeruginosa, Spirulina maxima, Scytonema varium]

(i) Brown algae appear brown or yellow-brown in color because they contain fucoxanthin pigment.
(ii) Macrocystis is a large kelp algae. It forms underwater kelp forests. Its length is 60 meters.
(iii) The region of Atlantic Ocean where Sargassum algae grows in abundance is called Sargasso Sea.
(iv) Many brown algae grow on seashore rocks.
(v) Antioxidants in brown algae are anti-cancer and enhance the human immune system.
(vi) Brown algae species number 2000.
Some brown algae- Macrocystis pyrifera, Sargassum muticum, Ascophyllum nodosum, Laminaria digitata, Fucus elastica etc.

(i) Diatom algae are golden-yellow in color. A complete diatom cell is called a frustule.
(ii) Their cell walls are strong, robust, composed of silica and richly ornamented bilayers.
(iii) They are called the ornaments of the sea or the living spectrum stones as they look very beautiful.
(iv) Dinoflagellate algae produce light in the darkness of night. The phenomenon is called bioluminescence (Noctiluca sp.).
(v) They have 10,000 species in 200 genera.
Some diatoms- Fragilaria capucina, Asterionella formosa, Tabellaria fenestrata, Navicula fossa, Noctiluca miliaris etc.