Algae can be unicellular,multicellular or colonial.Algae are found in ponds ,rivers and lakes etc.They have the characteristics of both plants and animals as some of the algae can prepare their own food by the process of photosynthesis because they have cholorophyll.However ,they are not classified as either of the two.Euglena, volvox,spirogyra are examples of algae.
In this article we will discuss about the morphological and cellular characteristics of algae.
Morphological Characteristics of Algae:
Algae exhibit a very wide range of morphological diversity. The simplest forms are unicellular, microscopic, motile or non-motile eukaryotic cells. They may be spherical (Protococcus, Chlorella), or pyriform (Chlamydomonas). When motile (Volvox, Chlamydomonas) the cells are generally provided with a pair of eukaryotic flagella. Diatoms show a characteristic type of non-flagellar locomotion.
Motile or non-motile algae may form a colony, known as a coenobium. There are also many multicellular algae. These may form uniseriate or multiseriate filaments which may be branched or un-branched. The branched filaments may have prostrate and erect branches (heterotrichous habit).
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The multiseriate filaments may form a cylindrical thallus or sometimes a flat thalloid structure. The siphonaceous algae have coenocytic body (multinucleate, without septa) which may be simple or complex and elaborate. The brown algae which are exclusively marine and always multicellular, often have large complex thalli. Diatoms are unicellular algae, but they have a cell which is unique. It consists of two overlapping halves or valves, like those of a petridish.
Some lower forms of algae have a doubtful systematic position. Many of them, like the chrysomonads are amoeboid. Euglenoids, have a flexible cell-covering. They are without a rigid cell wall and resemble protozoa in many ways. The dinoflagellates are also peculiar in having a typically flattened cell with an equatorial constriction, known as a girdle. However, all such atypical organisms are photosynthetic which justifies their inclusion in algae.