Subject: Biology
Algae are kept in division Thallophyta along with fungi. They differ from fungi in the presence of chlorophyll pigment and mode of their nutrition.
Sexual reproduction takes place by isogamy, anisogamy, and oogamy.
Isogamy
The fusion process of morphologically similar but physiologically dissimilar gametes is called isogamy. Male having the positive strain and female having negative strain are involved. Due to the opposite strains, they come close to each other and fuse together to form a diploid zygote. This process is also called conjugation.
Anisogamy
The fusion process of morphologically as well as physiologically different gametes is called anisogamy. The male is smaller and motile and female is larger and non-motile. Such types of gametes are called anisogamete and fusion process is called anisogamy or anisogamous sexual reproduction.
Oogamy
The fusion process of male gamete antherozoid and female gamete ovum or egg is called oogamy. Male gametes are developed in antheridium and female gametes are developed in archegonium. If the antherozoid and egg are developed in a separative reproductive sex organ fertilized product is zygote called oogamous type of sexual reproduction.
On the basis of dominant photosynthetic pigment, storage food material, and cell wall component division algae are divided into three classes;
S.N | Characters | Green algae | Brown algae | Red algae |
1 | Habitat | They are commonly found in fresh water. Some are terrestrial. | They are commonly found in cold marine water. Very few are freshwater. | They are commonly found in hot marine water.Eg; Batrachospermum is a freshwater red algae. |
2 | Habit | Unicellular and multicellular form are present. | Only multicellular form is present. | Unicellular and multicellular form are present. |
3 | Cellwall component | Cellulose, hemicellulose, and pectin. | Cellulose, pectin, algenic acid, ficoidin, and fucin. | Cellulose, pectin, agar and carrageenan. |
4 | Dominant photosynthesis pigment | Chlorophyll-a Chlorophyll-b carotene and xanthophyll | Chlorophyll-a Chlorophyll-c Fucoxanthin and fucocynin | Chlorophyll-a Chlorophyll-d r-phycoerythrin and allophycoerythrin |
5 | Storage food | Starch | Mannitol or laminarin | Floridian starch |
6 | Motile phase | Motile phase is present. | Motile phase is present. | Motile phase is absent. |
7 | Reproduction | It reproduce by vegetative, asexual and sexual methods. Sexually reproduce by isogamy, anisogamy, and oogamy. | It reproduces by vegetative, asexual and sexual methods. Sexually reproduce by anisogamy and oogamy. | It reproduces by vegetative, asexual and sexual methods. Sexually reproduce by oogamy. |
8 | Example | Spirogyra, volvox, Chlamydomonas. | Fucus, laminaria, actocarpus, sargassum. | Batrachospermum, Gelidium, polysiphonia. |
9 | It is represented about 7000 species. | It is represented about 2000 species. | It is represented about 5000 species. |
Molecular formula of;
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