Characteristics of algae:
· It is a unicellular or multicellular eukaryotic organism.
· Occurs in aquatic region.
· It is a photosynthetic organism. It consists of some pigment for the synthesis of food.
· They are autotrophs.
· Study of algae is known as phycology.
· Lives in ocean, fresh water, marine regions, ponds, lakes, soil, stones and tree barks.
· Some kind of algae can be seen only through microscope. They are known as planktons (or) phytoplanktons.
· Some algae can survive only at low temperature and some can survive at high temperature.
· Some kind of brown-pigmented algae contains flagella, forms algal mat on the surface of water.
· Some algae can survive at high salt concentrations, because they have adaptations.
· Some algae known as endophytic algae can survive only with in the host. It cannot live independently.
· Generally the algae are rod, spherical, spiral or club shaped.
· Some algae are flagellated and some are non-flagellated.
· Some algae can produce spores for reproduction.
· They contain discrete amount of nucleus, oil glands, vacuoles and pigments.
Reproduction of algae:
Algae reproduces by two types:
i) Asexual reproduction
ii) Sexual reproduction
· It is the vegetative mode of reproduction.
· Reproduces by any other part except seeds or spores.
· It takes place by gametes.
· It is of three types.
i) Isogamy (both spores are same)
ii) Heterogamy (two different spores are involved)
iii) Oogamy (female gametes are larger and non motile; male gametes are smaller and motile)
Based upon the pigments of algae they are classified into nine types:
i) Rhodophycophytae – red algae
ii) Xanthophycophytae – yellow green algae
iii) Chrysophycophytae – golden algae
iv) Phaeophycophytae – brown algae
v) Bacillaciophycophytae– the diatom
vi) Chlorophycophytae – green algae
vii) Euglenophycophytae – euglenoids
viii) Cryptophycophytae – cryptomonads
ix) Phyrophycophytae – dinoflagellated
· Also known as red algae.
· It is a marine algae i.e. it can survive only in marine regions.
· It is smaller in size up to 2-4 feets.
· It reproduces by asexual reproduction and produce non-motile spores.
· They have economic importance as it is used to produce geledium (agar).
· Also known as yellow green algae.
· Consists of yellow and green pigments.
· Produce single colonies and branched colonies.
· Reproduce by asexual reproduction.
· Cell wall consists of pectin.
· Consists of oil ducts and is found in moist soil region.
· Consists of flagella and amoeboidal in nature.
· It is pleomorphic (change its shape).
· Pigments and oils are stored with the help of silica.
· Reproduce by asexual method i.e. by binary fission.
· They are also known as brown algae.
· It is multicellular and consists of brown pigments.
· It has some adaptations such as hold fast and air bladder.
· Hold fast is used for binding with stones & air bladder is used for floating in the water surface.
· It reproduces by isogamy type of sexual reproduction.
· It plays major role in food, medicine & human consumption. Ex: sargassum
· They are also known as the diatom.
· It lives in fresh water, salt water and moist soil.
· Plays a major role as a food for aquatic animals.
· Produce single colonies (or) filamentous (linear form of colonies).
· Consists of nucleus and plastids (for photosynthesis).
· Outermost layer of the diatom is made up of silica and form shells.
· This is used to produce insulating agent and polishing agents.
· They are also known as euglenoids.
· They are motile, filamented algae.
· Reproduce by cell division.
· Cellulose, which is the outermost layer of the cell wall, is absent in it. So its cell wall is not rigid.
· It consists of eyespot, which is used to absorb sunlight during photosynthesis.
· It consists of vacuoles and fibres.
· During unfavorable conditions, it forms cyst (protect the cells by protective coating).
· They are also known as green algae.
· It is a kind of fresh water algae.
· Consists of well-defined nucleus and cell wall.
· Generally they are exhibited as reticulated (or) cup shape.
· Consisting of pigments known as pyrenoids, and apart from this it consists of hold fast also.
· Reproduce by zoospores and binary fission.
· Sexual reproduction – produce heterogamous, isogamous types of spores.
· Ex: Volvox, Ulothrix, Chlorella and Spirulina.
· It is a small group of biflagellated algae.
· Two flagella are entirely different from each other.
· Outer covering is made up of cellulose, and some of them apart from cellulose having plasmalemma in it.
· It consists of two plasmids.
· Food is stored as oils and starch
· Generally they reproduce by cell division and occasionally produce spores.
· It forms cyst during unfavorable conditions.
· It is also known as dinoflagellates.
· It is a marine freshwater algae.
· It is biflagellated.
· Flagella are attached with a girdle (mode of attachment).
· Flagella can move or rotate the cells.
· It can encircle the outer covering of algae with flagella.
· Cell wall consists of cellulose (outer) and plasmalemma (inner).
· Movement of this alga is faster than any other algae.