How are algae classified, and what are some examples of major algal groups?

Algae are classified into several major groups based on their pigmentation, cell structure, and reproductive characteristics. Some of the main algal groups include:
Green algae (Chlorophyta): These algae contain chlorophyll a and b, similar to land plants, and are found in a variety of aquatic habitats.
Red algae (Rhodophyta): Red algae are typically multicellular and are commonly found in marine environments. They contain pigments such as phycoerythrin and phycocyanin, which give them their characteristic red color.
Brown algae (Phaeophyta): Brown algae are primarily marine and include large, multicellular seaweeds such as kelp. They contain pigments like fucoxanthin, which impart a brown coloration.
Diatoms (Bacillariophyta): Diatoms are unicellular algae with intricate silica shells and are abundant in both freshwater and marine environments. They play a significant role in primary production and nutrient cycling in aquatic ecosystems.