Kelp is made by drying or burning algae. Kelp is used as poultry feed. Like- Laminaria, Mucus, Sargassum etc.

Algae is used as animal food in different countries of Europe. Such as Alaria, Laminaria, Rhodymenia, Ascophyllum, Sargassum, Fucus etc.

Algae act as producers in the food chain in water bodies. They produce sugary food in the process of photosynthesis.

(i) Food experts have identified 100 species of algae as human food. These algae are listed as nutritious foods as they contain protein.
(ii) Algae like Chlorella, Laminaria, Ulva, Chondrus, Gracilaria etc. have been used as human food since ancient times.
(iii) Arami and Kumbo prepared from brown algae are the most popular foods of the Japanese.
(iv) Nori in Japan, Jim in Korea and Laver in UK are made from Porphyra algae.
(v) Chlorella is a vitamin rich algae.
(vi) Spirulina is commented as the best food of the future.

1. Human food
(i) Food experts have identified 100 species of algae as human food. These algae are listed as nutritious foods as they contain protein.
(ii) Algae like Chlorella, Laminaria, Ulva, Chondrus, Gracilaria etc. have been used as human food since ancient times.
(iii) Arami and Kumbo prepared from brown algae are the most popular foods of the Japanese.
(iv) Nori in Japan, Jim in Korea and Laver in UK are made from Porphyra algae.
(v) Chlorella is a vitamin rich algae.
(vi) Spirulina is commented as the best food of the future.
2. Producer: Algae act as producers in the food chain in water bodies. They produce sugary food in the process of photosynthesis.
3. Animal food: Algae is used as animal food in different countries of Europe. Such as Alaria, Laminaria, Rhodymenia, Ascophyllum, Sargassum, Fucus etc.
4. Poultry food: Kelp is made by drying or burning algae. Kelp is used as poultry feed. Like- Laminaria, Mucus, Sargassum etc.
5. Oxygen production: Algae produce oxygen in the process of photosynthesis. Algae produce 60% of Earth’s oxygen.
6. Pollution control: Algae produce oxygen and absorb carbon dioxide. As a result, the purity of the atmosphere is preserved. Algae is used to treat sewage. Nitzschia (diatom) algae are used in water purification. Chlorella algae are used in air purification and sewage removal. As a result, environmental pollution is prevented.
7. Locating Marine Fish: Areas of the sea where there is a large amount of algae are found to have a large number of fish. The location of the fish is determined by satellite. As a result, a large amount of fish can be caught in a short time.
8. Biofuel production: Biofuel or Biodiesel is made from algae. So algae are called second generation biofuels. Botryococcus braunii algae is being used to make biofuel. Attempts are being made to produce biofuel from Chlorella and Scenedesmus algae. Recently, researchers are trying to produce third generation biofuels from microalgal biomass. Some micro-algal species Kirchneriella lunaris, Ankistrodesmus fusiformis, Ankistrodesmus falcatus, Chlamydocapsa bacillus, Chlorella, Scenedesmus etc. have been taken for biodiesel production.
9. Bio-fertilizer: Seaweed is used as a source of potash fertilizer. Such as Spirulina, Scytonema, Oscillatoria, Anabaena, Nostoc etc.
10. Determining the location of spy submarines: Blue-green algae contain pigment particles called phycobilin protein. These pigment particles (C-phycoerythrin, C-phycocyanin) absorb the diffracted rays from spy submarines. The location of the spy submarine is determined by the amount of absorbed radiation.
11. Diatomaceous earth: Diatomaceous (Navicula) algae bodies accumulate at the bottom of water bodies to form diatomaceous earth or diatomite. Soil age is determined by carbon dating the shells of diatoms deposited in the soil layer. Diatomite is used to make water filters, boilers, blast furnaces, metal polishes, toothpastes, etc. Diatomaceous earth was used to make dynamite.
12. Medicine: Agar agar is made from Gelidium, Gracilaria, Pterocladia etc., Goiter medicine is made from Sargassum and Laminaria and Chloreline antibiotic is made from Chlorella. Galactans are produced from the red algae Callophyllis variegate and Agardhiella tenera. Galactans are used to prevent HIV. Oral cancer drugs are made from algae containing beta-carotene, which has antioxidant properties.
13. Diseases control: Red algae increases immunity by producing white blood cells.
14. Aerospace research: Chlorella is used in space research to purify the polluted air of spacecraft. Chlorella fulfills the oxygen demand in space.
15. Importance of Industry
(i) Alum, glass, soda, potash, alginic acid and soap are made from seaweed kelp.
(ii) Ice-creams, jellies, paints, varnishes, shampoos and cosmetics are made from olgin of brown algae and gelatin of red algae.
(iii) Soap, paper, photography, rayon etc. are made from algae agar.
(iv) Polymers like starch and polyhydroxy-alkanoates are formed naturally in algae. Bioplastics are made from all these polymers.
(v) Carrageenan from algae (Chondrus crispus) is used in food processing, rayon, pharmaceutical industry, leather industry, toothpaste and dyes.
(vi) Algae (Furcellaria) furcellaran is used in making jam-jelly, preserving fish and meat and in toothpaste and pharmaceutical industry.
(vii) Algae (Gleopeltis furcata) is used in pulp and paper industry and for making glue.
(viii) Iodine and potash are produced from Laminaria algae.
16. Agar agar: Agar-agar is made from marine red algae (Gelidium, Gracilaria, Gigartina). It is used in the preparation of several types of food.
17. Petroleum and natural gas: Petroleum and natural gas are obtained from seaweed.
18. Fisheries: Different types of algae are used as fish food. So algae are used in ponds or reservoirs for fish farming. Several types of algae are used as feed in tilapia fish farming.
19. Nitrogen fixation: Algae like Nostoc, Anabaena, Aulosira etc. have heterocysts. Heterocysts fix nitrogen. These algae convert nitrogen into usable ammonia.
20. Nano filter making: A group of researchers from Dhaka University and Sweden’s Uppsala University have made nano filters from Pithophora algae. Nano filters are cellulose filters. It is like white paper and the pores of the filters are 17 nanometers. Waterborne microbes are 30-100 nanometers. So all viruses and bacteria are trapped in the filter. It is possible to separate toxic arsenic, ions, salts etc. from water.
21. Preparation of culture medium: Algae are widely used in the laboratory to prepare culture medium for bacteria and fungi.
22. Mosquito control: Mosquito larvae die in the presence of algae like Chara, Nitella etc. in water bodies. Mosquitoes can be controlled by cultivating these algae in water bodies.

1. Heplontic type: The organelles of this type of algae are diploid and the zygote is diploid in nature. eg Ulothrix.
2. Deplontic type: Gametes of these algae are haploid and organelles are diploid in nature. For example- Sargassum.
3. Isomeric type: Haploid and diploid organelles exist in this type of algae. Like- Laminaria, Macrocystis, Nerocystis etc.
4. Hetaromorphic type: The gametophytic state of these algae is haploid and
The sporophytic state is diploid. For example – Urospor.
5. Heplobiontic type: Two haploid stages and one diploid stage exist in their life cycle. eg Coleochaete.
6. Deplobiontic type: There are two diploid stages and one haploid stage in their life cycle. Eg- Polysiphon.

The process of sexual reproduction in which the male gamete is small and motile and the female gamete is large and stationary is called oogamy. A single ovule is produced in the female genitalia. A zygote unites with an egg to form a zygote. Such as Fucus, Oedogonium, Chlamydomonas, Vaucheria, Volvox, Chara, Polysiphonia, Sargassum etc.

The union of two gametes of different nature in terms of size, shape and structure is called anisogamy. Gametes that participate in sexual reproduction are called anisogametes. It can be flagellated and motile or non-flagellated and immobile. One is large in size and the other is small in size. Larger gametes are called macrogametes or female gametes and smaller gametes are called microgametes or pungametes. Such as Pandorina, Chlamydomonas, Caulerpa, Ectocarpus, Ulothrix etc.

The union of two gametes of the same nature in terms of size, shape and structure is called isogamy. Gametes that participate in sexual reproduction are called isogametes. It can be flagellated and motile or non-flagellated and immobile. Such as Ulothrix, Chlamydomonas, Spirogyra etc.

The process of sexual reproduction in which sperm and egg produced in different thallus combine to form zygote is called heterothelic sexual reproduction. eg Ulothrix.