What are the major groups of algae? | Biology | Extraclass.com

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This video will help you to learn What are the major groups of algae?

What are the major groups of algae?

How many different plants do you see every day?

You might have seen Grass, rose, marigold etc.

According to the Royal Botanic Gardens in the United Kingdom, there are about 3,91,000 species of vascular plants currently known to science, out of which about 3,69,000 species are flowering plants.

About 2,000 new plant species are discovered or described every year, many of which are already on the verge of extinction.

All plants are grouped under two main categories-

(1) Cryptogams

These are non-flowering and non-seed bearing plants which include: Thallophyta, Bryophyta and Pteridophyta

(2) Phanerogams-

These are plants which include:- Gymnosperm and Angiosperm.
Members of division Thallophyta are the most primitive and simple plants.

Their plant body is not differentiated into root, stem, and leaves.

Thallophyta includes Algae and Fungi.

Let’s begin by learning more about algae and it’s a classification

Algae are chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic organisms.

The algae are divided into three main classes:-

(1) Chlorophyceae,

(2) Phaeophyceae and

(3) Rhodophyceae.

Chlorophyceae- The members of Chlorophyceae are commonly known as green algae.

Their Plant body may be unicellular, filamentous and colonial.

Green algae usually have a rigid cell wall made of an inner layer of cellulose and outer pectose layer.

They are mostly grass green in colour due to the presence of pigments chlorophyll A and B.

Chloroplasts may be discoid, plate-like, reticulate, cup-shaped, spiral or ribbon-shaped in different species.

The food is mostly stored in the form of cellulose.

Phaeophyceae

The members of Phaeophyceae are commonly called brown algae and they are mostly found in marine habitats.

Plant body may be simple branched, filamentous form as in Ectocarpus to profusely branched forms, which may reach a height of 100 metres

The cell wall is made up of two layers, an inner cellulose layer and an outer layer made by gelatinous substances called align.

Major pigments are chlorophyll A, Chlorophyll C, carotenoids and xanthophylls.

They vary in colour from olive green to various shades of brown depending upon the amount of the xanthophyll pigment and fucoxanthin present in them.

Food is stored in the form of complex carbohydrates, which may be in the form of laminarin or mannitol.

Rhodophyceae

The members of Rhodophyceae are commonly called red algae.

Mostly red algae are marine and multicellular, some have complex body organisation.

Cell walls are made up of cellulose, pectin and polyesterate.

Major pigments present in their body are chlorophyll A, Chlorophyll D and R-phycoerythrin.

The food is stored as floridean starch which is very similar to amylopectin and glycogen in structure.


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