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Assignment of
Botany
Name: Rabia Aziz
Class: BS-1(Chemistry)
Topic: Chlamydomonas
Submit Date:
Submit To: Miss Yasmeen

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Chlamydomonas
Abstract:
1. Introduction
2.Morphology
3.Nutrition
4.Reproduction
5.Conclusion
6. References

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Introduction:
It is one of the most primitive
eukaryotic organisms in the
plant kingdom. It is widely
distributed freshwater and
free swimming green algae.
Thare are about 500 species.
Classification:
Kingdom: Protoctista
Division: Chlorophyta
Class: Chlorophyceae
Order: Volvocales
Family: Chlamydomonadaceae
Genus: Chlamydomonas
Morphology:
Motile unicellularalgae.

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Generally oval in shape.
Cell wall is made up of glycoprotein and non cellulosic
polysaccharidesinstead of cellulose.
Two anteriorlyinserted whiplash flagella. Flagella
originates from a basal granule located in the anterior
papillateor non-papillateregion of the cytoplasm.
Flagellum shows typical 9+2 arrangement of the
component fibrils.
Contractilevacuoles found at near the bases of flagella.
Prominent cup or bowl shaped chloroplast is present.
The chloroplast containsbands composed of a variable
number of the photosyntheticthylakoids which are not
organised into grana-like structures.
The nucleusis enclosed in a cup-shapedchloroplast,
which has a single large pyrenoid where starch is
formed from photosyntheticproducts. Pyrenoid with
starch sheath is present in the posterior end of the
chloroplast.
Eye spot present in the anteriorportion of the
chloroplast.It consists of two or three, more or less
parallel rows of linearly arranged fat droplets.

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Nutrition
Most species are obligate phototrophs but some are
facultative heterotrophs that can grow in the dark in the
presence of acetate as a carbon source.
Reproduction:

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Chlamydomonasreproduceby asexual and sexual means.
Asexual reproductionoccurs during the favourable as
well as unfavourable condition.The sexual reproduction
takes only underfavourable condition.
1. Asexual Reproduction
Chlamydomonasunder favourable season withdraws
flagella and it comes a resting stage. During this stage the
protoplasmwithdraws inwards from the cell wall and thus
the contractilevacuole disappears. It will be soon
followed by repeated longitudinal division of the
protoplasmgiving rise to 8- 16 daughter protoplasts.
Around each daughter protoplastcell wall is developed
followed by the formation of two flagella and becomes
parent like organism. These newly formed daughter cells
are called zoospores. Zoosporesare held inside the parent
cell wall, later it gets ruptured. Each of the zoosporethen
develops to new organism.
Chalamydomonasunder unfavourableseason also the
protoplasmdivide repeatedlyforming number of daughter
protoplast.This daughter protoplast does not develop
flagella and are known as endospore. These endospores
remain in the gelatinous matrix. This stage very much
resembles the alga Palmella, so known as the Palmella
stage. Under the onset of favourable season endospore
become zoospores.
2. Sexual Reproduction

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The Chlamydomonas during sexual reproductioninvolves
three stages. They are the;
a. Gametogenesis:The process of gametogenesis occurs
by repeated division of the protoplast giving rise to 16-32
gametes from a single cell. The gametes producedare
similar to zoosporewhich motile and biflagellate but
functions as gametes. These are later released to the
environment where the syngamy is supposed to take
place.
b. Syngamy: It is the process of fusion of gametes as a
result in the formation of zygote. These zygotes formed
will then transforms into zygospores. On basis of the
natureof the gametes fusing and mode of fusion three
kinds of syngamy are recognized. They are;
i. isogamy: The fusing gametes are identical in nature
so known a isogametes.
ii. Anisogamy: The fusing gametes are dissimilar and
motile so known as anisogametes.
iii. Oogamy: The fusing gamete in which the female
is non-motileand male is motile gamete.
c. Zygospore formation: Zygospore are the spores which
have thick wall to protect from the extreme environment.
Under favourable condition the zygospore germinates.
The diploid nucleus meiotically producesfour haploid
daughter nuclei. Then wall formation occurs which is
followed by the development of two flagella. The wall of

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the zygospore open and releases the daughter zoospores
which then give rise to vegetative organisms.
The lifecycle of chlamydomonasis known as haplobiontic
lifecycle.
Use:
Chlamydomonasis used as a model organism for research
on fundamental questions in cell and molecularbiology.
Conclusion:
Chlamydomonas, genus of green biflagellated single-
celled organisms of disputed classification, placed
botanicallyin the green algal order, Volvocales, and
zoologically in the plantlike protozoanorder, Volvocida.
Chlamydomonasis considered a primitive life-form of

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evolutionary significance. The more or less oval cells
have a cellulosemembrane (theca), a stigma (eyespot),
and a usuallycup-shaped, pigment-containingchloroplast.
Although photosynthesis occurs, nutrientsalso may be
absorbed through the cell surface. Asexual reproductionis
by zoospores; sexual reproductionis by formation of
gametes. The development of motility, sexual
differentiation, and gamete fusion seems dependent on the
production of substances (termones, gamones) that have a
regulatory action similar to hormones. There are some
500 species of Chlamydomonas,found in soil, ponds, and
ditches, where they may colourwater green. One species,
C. nivalis, which contains the red pigment hematochrome,
sometimes imparts a red colourto melting snow.
Reference: