Algae

Bharat Choudhary Reply 7:52 PM

BIOLOGY 


6. Algae

Introduction

These are chiefly plant like organisms found usually in water bodies and moist environments that are not subjected to direct sunlight. They make their own food by photosynthesis but theylack roots, leaves and other structures typical of true plants. They capture more of sun’s energy than all plants combined and form the foundation of most aquatic food webs. These are divided into 7 divisions one belonging to monera and the rest to plant kingdom.



Blue green algae (Cyanobacteria)

This belongs to the moneran division and contain a blue pigmentphycocyanin ,which in addition to chlorophyll but the chlorophyll is not located in chloroplasts rather it is found in chromatophores, infoldings of the plasma memrane where photosynthesis is carried out. It fixes atmospheric nitrogen. Some of this group likeGloeocapsa and Nostoc coexist with fungi to form Lichens. They give reddish colour to the Red sea. Euglenophycota is like Euglena found in stagnant water causes greenish colour and unpleasant flavour. Extensive quantities not desirable for drinking.

Green algae (chlorophyta)

These are found in fresh water and add more oxygen to water. Their excessive growth contaminate water . This unwanted growth can be removed by adding copper sulphate (CuSo4). Chlamydomonasis a green alage found in ditches,pools and even in artic . Spirogyrais green alage with a unique arrangement of its chlorophyll like a spirally twisted ribbon.


Brown algae 

The Brown colour is due to the presence of brown pigment,Flucoxanthin. They are the important sources of food for fish and other marine animals. They are also used as cattle feed, fertilizer. Its well known forms include Kelp (largest algae) and the sargassum weed.

Diatoms

They have colour ranging from yellowish green to yellowish brown containing silica. When they die, their skeletons are accumulated on the bottom of earth. This diatomaceous earth is used as insulating material for boilers, blast furnaces and refrigerators. It is also used as mild abrasive in polishes and scouring powders.

Red algae

These are characterized by reddish pigment phycobilin pigments . Most species grow near tropical and subtropical shores below the low tide mark and quite few are found on fresh water. Some secrete lime and there fore helped to build numours coral reefs . important edible varieties are Irish moss and laver(porphyra). Iris moss is used in curing leather, shoe polish and as an ingredient for creams and shampoos. Ceylon moss yield a gelatinous material known asagar-agar which is used as a medium for growing bacteria and fungi. Carrageenin obtained from Irish moss used as substitute for gelatin.

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