Algae | Plant or animal?

What is Algae?

Algae comprises a group of chlorophyll containing thalloid, autotrophic plants of the simplest type, without true roots, stems, leaves or leaf like organs. In the two kingdom classification, they are placed in the division Thallopyta along with fungai. But in five kingdom classification, the multicellular algae are included in the kingdom Plantae, unicellular eukaryotic in Protista and prokaryotic blue greens in monera.


Habitats of Algae

Algae occur in a variety of habitats Such as fresh water, on snow, on rock, and on or within the plant and animal bodies. But, aquatic forms are most common. The body of multicellular algae ranges from simple, floating colonial aggregation of cells to filaments or sheets of cells. Some algae are very complex and their thalli attain a length of 60 meters or more. The plants body is differentiated into holdfast,  stem like stipe and flattened leaf like blades

The three divisions of multicellular algae are-

1) Red ( Rhodophyta) have chlorophyll a, chlorophyll d and phycobilins pigments.

2)  Brown ( Phaeophyta) have chlorophyll a and chlorophyll c, which absorb red and blue light, and large amounts of the brown pigment, fucoxanthin.

3) Green (Chlorophta) are biochemically similar to terrestrial plants.


Reproduction in Algae

The algae reproduce by vegetative, asexual and sexual methods. Vegetative reproduction is usually by fragmentation. Asexual reproduction is by the production of different types of spores, the most common being the zoospores. The zoospores are flagellated structures and on germination give rise to new plants.

Sexual reproduction takes place through fusion of two gametes. The male and female gametes gametes may be similar in size. Such reproduction is called isogamous. Fussion of two gametes dissimilar in size is termed as anisogamous. Fusion between one large, non motile female gametes (egg) and a smaller, motile male gametes (antherozoid) is termed as oogamous.

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