Dr. P. Suganya
Department of Biotechnology
Sri Kaliswari College
Linnaeus in 1753 was first to introduced the term algae
(Latin- seaweeds) meaning, the Hepaticeae.
The algae (singular: alga) many of which are are unicellular.
Algae are ubiquitous, most of algae lives in aquatic
environment but many also thrive a terrestrial and a
Algae contains chlorophyll and are photosynthetic.
algae are of great general interest to all biologist because
single algal cells are complete organism capable of
photosynthesis and the synthesis of a multitude of other
compounds which constitutes the cell.
The branch that deals with the study of algae are known as
Algae chlorophyll bearing thalloid.
Algae are present everywhere in distribution.
They occur in great abundance in oceans, seas, ponds, fresh
water, steams and Salt Lake.
Many are found in soil of dam, rocks, stones, and bark of tree
and on other animals and plants surface.
Small aquatic forms make a large of the free floating
microscopic life in water, called plankton.
Phytoplankton is made up of plants i.e. algal forms.
Zooplankton is composed of animal organisms.
Some Species of algae grow on the snow and ice of polar region
and mountain peaks.
Some, algae grow in hot springes at temperature has high as
Some are Endophytice. They are not free living but live in other
organisms such algae are widespread in protozoa, molluscus,
sponges and corals.
Algae have a wide range of size and shapes.
Algae that occur as unicellular and they are spherical, rod-shaped,
club-shaped, or spindle shaped.
Many are multicellular and have understandable form, shape and
Algal cells are eukaryotic.
In most of the algal species cell wall is very rigid and thin.
Cell wall of diatoms are contain silica which makes them thick and
The motile algae have flexible cell membrane called Periplasts.
Algae contains a discrete nucleus.
Chlorophyll and other pigments are found in membrane bound
organelles known as Chloroplast.
Within the plastid matrix or stroma are found flattened membranes
vesicles called Thylakoid.
There are three kinds of photosynthetic pigments are present in
biloproteins or phycobilins
There are five chlorophylls: A, B, C, D and
Chlorophyll A is present in all algae.
Chlorophyll B – Euglenophycophyta, Cholorophycophyta.
Chlorophyll C– Xanthophycophyta, Bacillariophycophyta,
Chlorophyll D – Rhodophycophyta
Chlorophyll E – Xanthophycophyta.
There are two kinds of carotenoids:
Carotenes – linear, unsaturated hydrocarbon.
Xanthophyll – oxygenated derivatives.
Biloproteins or phycobilins
It is water soluble pigments.
Present in Rhodophycophyta.
Two types of phycobilins – Phycocyanin, Phycoerythrin
The are three main groups of algae being:
They are classified on the basis of following characteristics:
Primary photosynthetic pigments.
Cell wall composition.
Type and location of flagella.
CLASSIFICATION OF ALAGE
Habitat – Freshwater, Marine and terrestrial.
Photosynthetic pigments- Chlorophyll A and B carotenoid.
Cell wall components- Cellulose.
Storage food- Starch (stored inside the plastids).
Flagella- Two flagella per cell.
Asexual reproduction- reproduce vegetatively by fermentation
or by formation of mitospores.
Sexual reproduction- reproduction is of Isogamous,
Example- Chlamydomonas, Volvox, ulothrix, chara, ulva (sea
Example- Chlamydomonas, Volvox, ulothrix, chara, ulva (sea
GREEN ALGAE – CHLOROPHYCEAE
Habitat- Marine and freshwater.
Photosynthetic pigment- Chlorophyll A and D, carotenoids and
phycobilins. Commonly called red alage because of presence
of red pigment – phycoerythrin.
Cell wall components- Cellulose
Stored food- Floridian starch (alpha -1,4 glucon) stored in
Asexual reproduction- By fragmentation or by non-motile
Sexual reproduction- Oogamous and gametes are non- motile.
Example – Polysiphoria, Gracilaria and Gelidium.
RED ALGAE – RHODOPHYCEAE
Habitat- marine and freshwater.
Photosynthetic pigment- chlorophyll A and C, carotenoids and
Shades of brown depends on xanthophyll pigment,
Cell wall components- cellulose and alginic acid.
Cellulose is covered by a gelatinous coating of Algin.
Stored food- Laminarin, mannitol
Flagella- 2, unequal, lateral.
Asexual reproduction- by fragmentation or by motile
Sexual reproduction- is isogamous, anisogamous, Oogamous.
Example – Ectocarpus, Laminaria, fucus.
BROWN ALGAE – PHAEOPHYCEAE
Algae as primary producers- algae provides the base or beginning of most
aquatic animals or organisms because of their photosynthetic activities so
it is also known as primary producers of organic matter.
Commercial products from algae- many products are derived from algal cell
wall for economic value. Three of these are: Agar Alginic Acid,
and Carrageenan, are produced from the walls of algae.
Carrageenan is produced from the walls of several red algae. Species
of Chondrus, Gigartina are mostly used.
Agar is well known as a solidifying agent in the preparation of
microbiological media. It is obtained from red algae. Species
of Gelidium and Gracilaria are extensively used.
Alginic acid and its salts are obtained from the wall for brown algae.
Species of brown algae producing this compound include-
Macrocystis, Laminaria, Fucus.
Algae as food- many species of algae are (mostly red and brown algae) are
used as food in the far east.
Red algae one of the most important is Porphyra: it is used as food in
Japan where it is called
Other red algae such as Chondrus, Nemalion are locally collected and
ECONOMIC IMPORTANCE OF ALGAE
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