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Chapter: 11th 12th standard bio zoology Human Body higher secondary school

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Classification of Algea

1. Chlorophyceae 2. Xanthophyceae 3. Chrysophyceae 4. Bacillariophyceae 5. Cryptophyceae 6. Dinophyceae 7.Chlromonodineae 8.Euglenophyceae 9. Phaeophyceae 10. Rhodophyceae 11. Myxophyceae

Classification of Algea

 

F.E. Fritsch (1944-45) classified algae into 11 classes in his book 'Structure and Reproduction of Algae' based on the following characteristics.

1. Pigmentation 2. Reserve food 3. Flagellar arrangement 4. Thallus organization 5. Reproduction.

 

The 11 classes of algae are:

1. Chlorophyceae  

2. Xanthophyceae  

3. Chrysophyceae

4. Bacillariophyceae        

5. Cryptophyceae    

6. Dinophyceae  

7. Chlromonodineae 

8. Euglenophyceae 

9. Phaeophyceae 

10. Rhodophyceae 

11. Myxophyceae



Thallus organization

 

The thalli of algae exhibit a great range of variation in structure and organization. It ranges from microscopic unicellular forms to giant seaweeds like Macrocystis which measures up to 100 meters long. Some of them form colonies, or filaments. The unicellular form may be motile as in Chlamydomonas or non-motile as in Chlorella. Most algae have filamentous thallus. eg. Spirogyra. The filaments may be branched.

 

Cell Structure & Pigmentation

 

With the exception of blue green algae which are treated as Cyanobacteria, all algae have eukaryotic cell organization. The cell wall is made up of cellulose and pectin. There is a well defined nucleus and membrane bound organelles are found.

 

Three types of Photosynthetic pigments are seen in algae.          

They are 1. Chlorphylls 2. Carotenoids 3. Biliproteins.

 

Nutrition and reserve food materials in Algae

Algae are autotrophic in their mode of nutrition. The carbohydrate reserves of algae are various forms of starch in different classes of Algae. For example, in Chlorophyceae, the reserve food is starch and in Rhodophyceae it is Floridean starch, in Phaeophyceae it is laminarian starch while in Euglenophyceae it is paramylon. Members of Phaeophyceae storemannitol in addition to carbohydrate. Members of Xanthophyceae and Bacillariophyceae store fats, oils and lipids. The nature of reserve food material is also another important criterion used in classification.


Arranagement of Flagella

 

Flagella or cilia( sing.flagellum / cilium) are organs of locomotion that occur in a majority of algal classes. There are two types of flagella namely whiplash (Acronematic) and tinsel (pantonematic).

 

Reproduction

 

Three common methods of reproduction found in Algae are 1. Vegetative 2. Asexual and 3. Sexual

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