GENERAL CHARACTERS, HABITAT, THALLUS
Algae are small autotrophic plants that fail to show any cellular
differentiation. In simple we can call it chlorophyllous thallophytes.
ALGAE IN LATIN MEANS SEA WEEDS
The Algae word first used by Carolus Linnaeus 1753
(For a group of Bryophytes)
The actual delimitation
of a group plants from their macroscopical features
naming as Algae was done by Antoine Laurent De
The branch of botany under which we study about Algae is known as
The father of Algology is Felix Eugen Fritsch
The father of Modern Algology is William Henry Harvey
The Indian father of Algology is M.O.P. Iyengar
The book wrote by F.E. Fritsch was “The Structure and Reproduction of Algae”
Vol. I & II 1935
The two main phycologist of india work on algae are:
R. N. Singh- N2 fixing with the help of Blue Green Algae
P. K. Dey- Pioneer of N2 fixation
Algae are simple, thalloid, autotrophic, non vascular having unicell sex
organs (exception multicellular sex organ in Chara) and no embryo formation (embryo 1st
In algae embryo did not formed because of zygotic meiosis. Due to zygotic meiosis haploid nuclei
are formed which further grow in to the new plants. Algae generally are Haploid in nature and for
very little duration diploid stage comes in the form of zygote. (If mitosis occurs in zygote results in
the formation of Embryo)
Unicellular Prokaryotes Monera
ALGAE Unicellular Eukaryotes Protista
Multicellular Eukaryotes Plantae
Algae differ from Bacteria in being eukaryotic in nature (except BGA)
Algae differ from Fungi in being autotrophic in nature
Algae differ from Bryophytes in not having a jacket of sterile cells
around their reproductive structures (except Chara, Bryophytes has
multicelled sex organ covered by sterile cell jacket while Algae has single cell sex organ
and are exposed)
BGA differ from bacteria in having oxygenic photosynthesis, it takes
water as electron donor and release O2 while Bacteria take electron
from hydrogen sulphide
In Algae oxygenic photosynthesis occurs due to Chl. a
I. Habit: Algae are
Unicellular = Single
Multicellular = Colony/Filamentous
II. Habitat: Algae may be
1. Aquatic Algae
2. Terrestrial Algae
3. Aerial Algae
4. Algae of Unusual Habitats
1. Aquatic Algae may be
A. Fresh Water Still Water ( EX. Chara, Oedogonium, Zygnima)
Running Water ( Has Holdfast for attachment, EX.
Vaucheria, Ulothrix, Cosmopogan)
B. Marine Algae = Members of Phaeophyceae and Rhodophyceae like
Ectocarpus, Polysiphonia, Sargassum, Ulva.
Terminologies used for Aquatic Algae:
Habit Habitat Example
1. Benthophytes Algae remains attached to any
substratum ( growing on mud and
other bottom )
The Benthic Algae may be
Grows on Sediments Located on Sand
Ex. Porphyra Ex. Sargassum
Fresh Water are
Marine are members
of Phaeophyceae and
2. Epactiphytes Growing along shores of lakes or
3. Neustonic They grow on water surface Ex. Hydrodictyon
Habit Habitat Example
4.Thermophytes Growing in thermal water can tolerate
very high temperature
Based on temp.
Hypothermae ( Below 18 ‘C)
Hliarothermae (18- 30 ‘C)
Euthermae (30 -50 ‘C)
Aerothermae (50 -70 ‘C)
Hyperthermae ( Above 70’C)
Majority of thermal
algae belongs to
Ex. Synechococus elongatus,
5. Planktophytes Floating Algae.
Are of two types:
1.Euplanktophytes: True floating Algae
ex. Volvox, Hydrodictyon
floating accidentally ex. Oedogonium,
Ex. Spirulina, Volvox,
Abundant growth of planktonic algae begin to impart colour to the water, such
phenomenon is called Water Bloom as caused due to algae so called as Algal Water
Bloom. Formation of blooms depends on temp. increase and nutrient availability.
Water Bloom may be
1. Temporary & Mixed type are produced by Chlamydomonas, Scendesmus,
Chlorella, Ankistrodesmus, Pediastrum etc.
2. Temporary & Pure contains only one species Volvox globator or Chlamydomonas
3. Permanent & Mixed are made up of Anabaena, Anabaenopsis, Microcystis etc.
4. Permanent & Pure
a. Trichodesmium sp forms a permanent red water bloom in red sea.
b. Microcystis aeruginosa forms permanent blue green water bloom in temple
Habit Habitat Example
6. Halophytes Growing in saline habitat
In salt lakes ex. Chlamydomonas
In salt springs ex. Enteromorpha sp.
7. Epiphytes Growing attached on other plants or
Epiphytic algae on submerged
hydrophytes known as Periphyton
association with Chara
Cladophora on leaves
of Vallisneria &
8. Epizoophytes Grows on aquatic organisms Cladophora crispata on
Protoderma on Turtle
2. TERRESTRIAL ALGAE
Algae that grows on or in soil called as Edaphophytes
a. Sapophytes- Algae grows on the soil surface ex.
b.Cryptophytes- Algae grows in the soil, fix nitrogen for
the soil fertility ex. Nostoc, Anabeana
3. AERIAL ALGAE
Habitat is aerial and are called as Aerophytes
Habit Habitat Example
1. Epiphyllophytes Grows on the leaves of terrestrial plants Trentopholia sp on the
leaves of Butea
Growing on the Mosses, Liverworts and on the
3. Epizoophytes They grow on the body of terrestrial animals Ex. Cyanoderma on the
hairs of Sloth Bear
4. Lithophytes Growing attached to stones and rocky surface
a.Epilithic- On rock surface ex. Calothrix
b.Endolithic- Inside the rock or inside the
skeleton of corals ex. Dalmatella
c.Chasmolithic- Grows in rock fissures ex.
4. Algae of Unusual Habitat
A. Cryophytes: Algae grow on Ice or Snow
Only on snow- Raphidonema
Only on ice- Ancyclonema
On both ice & snow- Trachiscia
Not true cryophytes-Phormidium
In Europe some mountain become green colour due to Raphidonema
Yellowishgreen due to Chlamydomonas yellowstonensis
Red colour due to Chlamydomonas nivalis (Arctic & Alpine Region)
Brown colour due to Ancyclonema nordenskioldii
Yellow colour due to Protoderma
Green colour due to Scotiella
Some Algae live in association with certain Plants and Animals
1. Endophytic Algae: With Plants
Nostoc in Anthoceros
Anabeana cycadeae in the corolloid root of Cycas
BGA Cyanailae in Protozoa
2. Endozoic Algae: With Animals
Zoochlorella in Hydra viridis
Trochisia sp. In Rana agilis
Oedogonium undulatum in Insect Larva
Oscillospira sp. In Guinea Pig
C. Parasitic Algae
Some BGA like Simonosiella sp. are found as
parasite in the Human Intestine
Cephaleuros virescens grows on the leaf of Thea
sinensis (Tea Plant) and cause the disease
known as Red Rust
III. THALLUS ORGANIZATION
Vegetative body of Algae is called as thallus
It is not differentiated in to Root, Stem and Leaf, so algae are simple plants
A. Unicellular- All vital function of life performed by a single cell, these are of
1. Flagellated/Motile Form: Have flagella
One Flagella ex. Trachelomonas, Chromulina
Two Flagella- When both flagella are equal in size is called Isokont
ex. Chlamydomonas, Haematococcus
When both flagella are unequal in size called Hetrokont ex. Gonyostomum
2. Amoeboid/Rhizopodial Form
Having protoplasmic projection called pseudopodia
3. Non Motile/Coccoidal Form
Lack cell wall and no locomotary organ ex, Diatoms, Chlorella
B. MULTICELLULAR THALLUS: Multicelled Thallus
1. Colony: It is formed by the aggregation of individual cells
a. Coenobium- A colony with definite numbers of cells and having a constant
shape and size
Non Motile :
Aggregations of non-motile cells in the form of a colony (non-motile) are
common only in Chlorophyceae. Here the cells are, more or less, fused
together (e.g., Hydrodictyon) or connected by mucilaginous threads (e.g.,
Dictyosphaerium) and the colony may be of various shapes. It may be plate
like e.g.. Scenedesmus or net-like as in Hydrodictyon.
Motile flagellated cells aggregate together to form motile
colonies. Colonies vary in shape and size and in the number of cells.
The colonies are either “plate-like” (e.g., Gonium) or spherical
In a large number of genera this habit is a permanent one e.g., Tetraspora
(Chlorophyceae), Phaeocystis (Chrysophyceae) or is a temporary phase, in the life-
cycle e.g., Chlamydomonas (Chlorophyceae) Chromulina, (Chrysophyceae). The
habit is named after the genus Palmella (Palmeflaceae, Chlorophyceae)
Here the individual lion-flagellated cells have mucilaginous sheaths around
them and are enveloped in a common gelatinous matrix of indefinite shape which
may be microscopic or macroscopic in size.
A variation of the palmelloid condition is seen in
dendroid colonies. Here the mucilage is produced locally, generally at the
base of the cell.
Dendroid forms are seen e.g. Prasinocladus (Chlorophyceae),
Mischococcus (Xanthophyccae) and in Chrysophyceae and Euglenineae
2. Filamentous Forms:
the division of the single cell into many daughter cells with septa between the divided
cells a filamentous type of construction would be formed.
(i) Un-branched Filaments:
Simple un-branched filaments are found in many forms. They are either
free-living e.g., Spirogyra or attached, at least initially e.g., Oedogonium, or
aggregated in colonies e.g., Nostoc
(ii) Branched Filaments:
A simple branched filament with dichotomous branching pattern and a basal
attaching cell, holdfast or hapteron is common with many types e.g.,
Cladophora. A peculiar form of branching, known as ‘false’-branching is
observed in Cyanophyceae e.g., Scytonema
This most highly evolved type of plant-body, showing a good amount
of division of labour.
The plant-body consists of two distinct parts:
(1) A basal or prostrate creeping system, and
(2) An erect or upright system.
The prostrate system is attached to some substratum, grows apically and
gives rise to numerous photosynthetic and rhizoidal filaments. Rhizoidal filaments
sometimes penetrate the substratum . The erect system develops from the prostrate
system and is composed of one or more and usually branched photosynthetic filaments.
In Stigeoclonium and Trentepohlia these two systems are equally
developed and easily distinguished.
Whereas in Coleochaete (Chlorophyceae) and Ascocyclus (Phaeophyceae) the
prostrate system is highly elaborated and the erect system is reduced. This
gives the body a discoid type of appearance. On the other hand, in many
species of Ectocarpus, the prostrate system is reduced, and the erect system
is well developed. This gives the body a crust or cushion type of appearance.
In many cases the reduction of one system has gone to the limit of practical
elimination. Thus in an endophytic species, Endoderia and in Chaetopeltis
(Chlorophyceae) only the prostrate system is developed. Complete absence
of prostrate system is noticed in Microthamnion.
(iii) Pseudoparenchymatous forms:
As indicated by the term ‘pseudo’ = false, the plant body gives the
appearance of parenchymatous construction. The pseudoparenchymatous
structure is a secondary development, close association of cells is a result of
interweaving of filaments. Intercellular connections may be densely packed
and firmly coherent (e.g., Dumontia, Rhodophyceae) or, the association may
be loose and can easily be separated by pressure (e.g., Castanea,
Two types are: (1) uniaxial construction = a single colourless central axial
filament e.g., Batrachospermum
(2) multi-axial = many filaments e.g., Polysiphonia
5. Siphonaceous Forms:
In a number of algae, belonging to Siphonales e.g., in Vaucheria, Botrydium,
the growth of the plant body takes place without the usual cross-wall
formation except during formation of reproductive organs. Thus a ‘tube’-
like multinucleate structure, or a coenocyte, is produced.
6. Parenchymatous Forms:
Parenchymatous thallus organization also is a modification of the
filamentous habit, with cell division in more than one plane. The
parenchymatous thalli may be ‘leaf-like’ or foliose, tubular or highly
Foliose or Tubular thalli are formed by the division of the cells two or
three planes. Common examples of foliose structures in Viva
(Chlorophyceae), Porphyra (Rhodophyceae). The example of tubular
structure is Enteromorpha (Chlorophyceae).
Reproduction Found in Algae
There are three common methods of reproduction found in algae – (i)
vegetative, (ii) asexual, and (iii) sexual.
1. Vegetative reproduction:
This may be of several types.
(i) By cell division:
The mother cells divide and the daughter cells are produced, which become
new plants. This is exclusive type of reproduction in Pleurococcus, some
desmids, diatoms, Euglena, etc.
The plant body breaks into several parts or fragments and each such
fragment develops into an individual. This type of vegetative reproduction is
commonly met within filamentous forms, e.g., Ulothrix, Spirogyra, etc. The
fragmentation of colonies also takes place in several blue green algae, e.g.,
Aphanocapsa, Aphanothece, Nostoc, etc.
(iii) Hormogone formation:
When the trichomes break in small pieces of two or more cells, such pieces are called
‘hormogones’. Each hormogone develops into a new plant, e.g., Oscillatoria, Nostoc, etc.
(iv) Hormospores or hormocysts:
They are thick-walled hormogones, and produced in somewhat drier conditions.
(v) By adventitious thalli:
Certain special structures of thalli are formed which help in vegetative reproduction. The
well known propagula of Bryopsis, Sphacelaria and Nereocystis are good examples.
(vi) By primary secondary protonema:
Such thread-like vegetative bodies develop in the case of Chara, which help in
Usually these bodies are rounded and filled up with abundance of starch. Each body may
give rise to a new plant, e.g., Chara.
(viii) Starch or amylum stars:
Such special star-shaped, starch filled bodies give rise to new plants frequently reported
Small bud-like structures. Usually develop on the rhizoids of Chara are called bulbils. Each
such bulbil may develop into a new plant.
In most of the Chlorophyceae members, the Akinetes are developed. Usually the protoplast
of each cell converts in a single akinete. Sometimes they are formed in chains. Each
akinete may develop into a new plant, e.g., Oedogonium, Ulothrix, etc.
2. Asexual reproduction:
Usually the protoplast of a cell divides into several protoplasts and thereafter they escape
from the mother and develop into new plants.
(i) By zoospores:
The zoospores are formed from certain older cells of the filaments. The cytoplasm divides
to form zoospores which are escaped from the mother cell. They are always formed in
favourable conditions. The zoospores are always motile. They may be (i) biflagellate, (ii)
tetraflagellate, (iii) stephanokontean type of zoospores, e.g., Oedogoniales and (iv)
compound zoospores, e.g., Vaucheriaceae
(ii) By aplanospores:
When motile phase of zoospores is eliminated, the bodies are called
aplanospores. The aplanospores develop in unfavourable conditions. Each such
spore is surrounded by a wall.
(iii) By hypnospores:
Actually they are very thick-walled aplanospores and develop only in adverse
conditions, e.g., Pediastrum, Vaucheria.
(iv) Palmella stage:
Here the successive generations of divided cells are gelatinized and a thick
mucilaginous envelope develops, e.g., Chlamydomonas, Ulothrix, etc.
They are just like aplanospores except that they are smaller in size. They
resemble in shape to mother cell except in size. Each autospore gives rise to a
new plant. Such autospores are reported from many Chlorococcales.
In many blue green algae and Bacillariophyceae, the endospores are formed
within the cells. On the approach of favourable conditions, each endospore
develops in a new individual.
They are found in the carposporophytes of red algae (Rhodophyceae). Each such spore
develops in a new individual.
(ix) Tetra spores:
These spores develop within monosporangia. Each spore gives rise to a new plant, e.g.,
many members of Rhodophyceae (Bangia, Porphyra, Porphyridium, etc).
Such spores are reported from many members of Rhodophyceae. Each spore develops into
a new plant.
They are found in Xanthophyceae and Bacillariophyceae where they act as perennating
(xiii) Daughter colonies:
In many Volvocales and Chlorococcales, the daughter colonies are developed asexually,
e.g., Volvox, Hydrodictyon, Pediastrum, etc.
(xiv) Gongrosira stage of Vaucheria:
In the aseptate filaments of Vaucheria, the protoplast divides into several parts, several
hypnospores or cysts are produced and the whole filament looks like an algal form
They are produced in many Bacillariophyceae.
It is greatly advanced method of reproduction and not known in Myxophyceae
(blue green algae). There are two main types, i.e., (i) isogamy and (ii)
The fusion of similar motile gametes is found in many species. Usually the
gametes taking part in fusion come from two different individuals or filaments,
sometimes these gametes come from two different cells of the same filament.
Thousands of gametes come and aggregate in clumps. (See Fig. 3.8).
The fusion of dissimilar gametes is called heterogamy. There are variations of it.
The motile gametes taking part in fusion may either differ in size (morphological
anisogamy) or physiological behaviour (physiological anisogamy).
In this case, the male antherozoid fuses with the female egg. This fusion may be
of primitive type as found in Cylindrocapsa, or advanced type as in Oedogonium,
Vaucheria, Chara, Polysiphonia, etc.
(iii) Aplanogamy or conjugation:
It implies the fusion of two non-flagellate amoeboid gametes (aplanogametes).
They are morphologically similar but physiologically dissimilar, e.g., order
In fresh water algae, the sexual reproduction is best means of perennation because
it is followed by the formation of thick-walled zygote or oospore.
The female gametes convert into zygotes without fusion. The resultants are called
azygospores or parthenospores and the phenomenon ‘parthenogenesis’, e.g.,
Spirogyra, Oedogonium and many others.
In this phenomenon, the fusion of the daughter protoplasts or of the divided nuclei
of a cell without liberation takes place. This process is known in many diatoms and
Offenbar haben Sie einen Ad-Blocker installiert. Wenn Sie SlideShare auf die Whitelist für Ihren Werbeblocker setzen, helfen Sie unserer Gemeinschaft von Inhaltserstellern.
Sie hassen Werbung?
Wir haben unsere Datenschutzbestimmungen aktualisiert.
Wir haben unsere Datenschutzbestimmungen aktualisiert, um den neuen globalen Regeln zum Thema Datenschutzbestimmungen gerecht zu werden und dir einen Einblick in die begrenzten Möglichkeiten zu geben, wie wir deine Daten nutzen.
Die Einzelheiten findest du unten. Indem du sie akzeptierst, erklärst du dich mit den aktualisierten Datenschutzbestimmungen einverstanden.