Algae

Algae are simple, autotrophic, plant-like organisms that live mostly in water. Like green plants, they are photosynthetic and prepare their own food using sunlight, water and carbon dioxide:

This chapter covers their general characteristics, their three main classes, and a detailed study of the green alga Spirogyra.

Introduction

The term algae is derived from the Latin word alga, meaning seaweed. The study of algae is known as phycology or algology. According to Smith (1955), there are about 1560 genera and 17535 species of algae.

General characteristics

• They are autotrophic thallophytes.
• They are aquatic in habitat.
• The thallus ranges from a simple unicellular form to a highly complex multicellular form.
• The cell wall is made up of cellulose.
• The reserve food is stored in the form of starch.
• The photosynthetic pigments are chlorophylls, carotenoids, xanthophylls and phycobilins.
• Reproduction takes place by vegetative, asexual and sexual methods.
• Asexual reproduction takes place by motile and non-motile spores.
• Examples: Spirogyra, Laminaria, Zygnema, etc.

Types of algae

Algae are grouped into three main classes:

1. Chlorophyceae (green algae)
2. Phaeophyceae (brown algae)
3. Rhodophyceae (red algae)