Question

To which division does red, brown and green algae belong to?

Answer 1

Hint: Algae exist in a wide range of environments like oceans, rivers, and lakes to ponds, brackish waters and even in snow. Algae are usually green, but they can also brown and red in colour. Red coloured algae are usually found in snow and they contain carotenoid pigments in addition to chlorophyll which gives them a distinct red colour.

Complete answer:
Algae can be described as a large and incredibly diverse group of eukaryotic, photosynthetic life forms which do not share a common ancestor and are not related to each other. Algae belongs to the division Thallophytes.

The scientific name of Red Algae is Rhodophyta and they are included in the Class Rhodophyceae. They are mostly found in the freshwater lakes. They are the oldest type of eukaryotic algae. They are called so because of the presence of a pigment called chlorophyll A, phycocyanin, and phycoerythrin. Phycoerythrin gives them the characteristic red colour.

The main features of red algae are:
- They lack flagella and centrioles
 - Photosynthetic pigments are present
- They exhibit biphasic or triphasic life cycle patterns.
- The structure can be described as multicellular, filament, blade structure.
- Food is stored in the form of starch and polymers of galactan sulphate
- The mode of nutrition can be saprophytic, parasitic or also epiphytic.
- Their cell walls are made up of cellulose and many different types of carbohydrates.
- Cytoplasmic connections are maintained through the presence of pits in cell walls.
- Sex organs are known as spermatangium which is the male sex organ and the female sex organs are called carpogonia or procarp.

Characteristics of the brown algae are:
- They contain special gas-filled bladders called pneumatocysts which are present near the lamina. Its function is to provide buoyancy to algae
- Their cell wall is made up of algin and inner cellulose, which provides strength to the membrane.
- They contain chlorophyll a, c, carotenoids and xanthophyll. Fucoxanthin is the main xanthophyll pigment and this pigment is responsible for their characteristic colour.
- Food is stored in the form of complex carbohydrates which are laminarin or mannitol.

Characteristics of green algae are:
- The primary photosynthetic pigments are chlorophyll a and b, along with auxiliary pigments such as xanthophylls and beta carotene.
- Green algae are used to conduct photosynthesis for higher organisms.
- Spirogyra, Ulothrix, Volvox are examples of green algae.

Note: Algae is classified into;
- Pyrrophyta
- Euglenophyta
- Red algae or Rhodophyta
- Brown algae or Phaeophyta
- Green algae or Chlorophyta
- Yellow-green algae or Xanthophyta
- Golden-brown algae or Chrysophyceae.

Algae act as natural source of food for fish and other aquatic animals. Red alga is the most important commercial food in Japan. Agar or agar-agar is extracted from algae. It is a substance which is used as used in puddings, dairy toppings and other instant food.