Algae are a group of unicellular or multicellular, eukaryotic and autotrophic organisms. This article explains the important characteristic features of these organisms, types of Algae present in nature and also the economic importance of this group of organisms.
Algae is a group of organisms include unicellular organisms as well as multicellular organisms. Chlamydomonas, Chlorella, Diatoms like single-celled organisms with a eukaryotic organization, will fit into Kingdom Protista. Multicellular algae-like Volvox, Cladophora, Sargassum with eukaryotic and autotrophic nature will fit into Kingdom Plantae. Depending on the pigment present in algal organisms, these organisms are green, blue-green, brown, golden-brown, and red in color. More than one million species of algae are presently existing in nature. The study of algae is known as Phycology and the person who studies algae is known as Phycologist.
Image of green algae (Courtesy:-wikipedia.org)
Important characteristic features of Algae
The size of algae ranges from microscopic like Chlamydomonas, Diatoms to giant kelps 60 meters length. Smallest unicellular organisms have single cells whereas the largest algae will have millions of cells. Algae include organisms from very simple microscopic to highly complex macroscopic.
Algae can grow in suspended water, grow on the surface of the water, grow in snow and ice, grow in hot springs, grow in soils, grow on animals. So algae adapt to live in different habitats.
Some algae have only one cell while others have many cells. Some algae form colonies that are made up of many single-celled algae. These single-celled algae are glued together by mucilage material to form colonies like in Volvox. Some algae like threads called filaments which are also attached to each other to form colonies. Many varieties of algae have jelly-like cell coverings which give them slimy nature and hard to grasp inside water. These cell coverings help the algae from losing water and protect themselves from unfavorable conditions.
Multicellular algae which belong to Thallophyta in their body organization lack roots, stem, and leaves. They lack conducting tissues like xylem and phloem as in higher plants. Ex:- Mosses, Liverworts, Hornworts.
As algae mostly contain green chlorophyll pigment and as they photosynthetic autotrophs they can prepare their own food like higher plants. The reserve food material from simple to largest algae is only starch.
The different colors of algae are due to different pigments present as chlorophylls, carotenoids, phycobiliproteins and different groups of complex pigments. Because of the different pigments present in algae along with chlorophyll, the algae will be green, blue-green, brown, golden brown and red in color.
Algae reproduce both asexually and sexually. All algae reproduce asexually by fission in which a single cell divides into two forming two algae. When algae in a colony reproduce by fission, the number of cells in the organism increase and the organism grows bigger. Many algae reproduce by spores in asexual reproduction. The spores swim around freely like tiny animals. Later, they settle against some object. Some spores form new algae immediately. But some algae remain dormant for long-duration till the conditions become favorable and then grow into new algae.
Some algae reproduce by sexual methods. These organisms reproduce by sex cells called gametes. The male sex cell is known as sperm and female sex cell is known as an egg. The male and female gametes fuse together to form a zygote. Some zygotes form new algae immediately. In some cases, zygotes remain dormant for some time but develop into new algae after the return of favorable conditions.
Types of Algae
These are one-celled organisms mostly found in fresh and saltwater. They can be found in every stream, ponds, and ditches. They are usually found in colonies. Mostly these algae look blue-green in color but some varieties are black or red. They reproduce by fission method. They grow best in the summer season. They give a fishy odor and taste to water. The pigments present in these organisms are chlorophyll, chlorophyll a, carotenoids, phycobilin, phycoerythrin. Blue-green algae are commonly known as Cyanobacteria which belongs to Kingdom Monera since they contain prokaryotic cells. Ex:- Nostoc, Anabaena, Oscillotoria.
These algae are found in freshwater, saltwater, and on land. Some green algae are one-celled whereas others form large colonies. These algae reproduce by fission, others by spores, and still others by sexual cells. Green algae include chloroplast and chlorophylls, carotenoids (carotenes and xanthophylls) and phycobilins in them. Ex:- Spirogyra, Ulva
The brown algae are found in saltwater usually near the seashore. Some brown algae are very small but others grow as long as 46 meters. Some of the larger brown algae are attached to rocks along the seacoast commonly called kelp or seaweeds. They have air bladders with air in them which helps them to float. Smaller brown algae reproduce by fission or by spores. The larger brown algae reproduce through gametes by sexual reproduction. Brown algae include a brown pigment called fucoxanthin along with Chlorophyll a and c, beta-carotene and other xanthophylls. Ex:-Fucus, Sargassum
Diatoms are exclusively one-celled tiny golden-brown in color. They are different kinds of shapes like round, oval, triangular, rectangular, spindle-shaped, or boat-shaped. Their cell walls are filled with a glass-like material called silica. Diatoms reproduce by fission. The pigments found in Golden-brown algae include chlorophylls a and c, and the accessory pigments are carotenoids and xanthophylls.
Red algae are mostly found in saltwater and these algae are small in size. Some red algae grow in shallow water and others grow in deeper water. They grow always attached to solid objects. Some red algae reproduce by fission or spores asexually while others reproduce by gametes sexually. Phycoerythrin pigment present in these red algae is the reason for this color. Ex:-Chondrus, Mastocarpus
Economic importance of Algae
Algae are the source of food for many aquatic animals.
As algae have chlorophyll and can carry photosynthesis, they can give off oxygen to for the aquatic animals to breathe.
Blue-green algae and Seaweeds are used for fertilizing lands by farmers.
The materials extracted from algae are used in making soups, gelatins and a variety of foods.
Algae are used to make ice creams smooth and in salad dressing as a thickener.
Agar agar, a jelly-like material prepared from some algae will be used in hospitals and laboratories for growing bacteria for research purpose.
Algae will be used in space flights to provide fresh oxygen for astronauts and also to remove carbon dioxide.
Being the most popular educational website in India, we believe in providing quality content to our readers. If you have any questions or concerns regarding any content published here, feel free to contact us using the Contact link below.