classification, ecology and reproduction of some algae

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Scientific Classification
Volvox belongs to the following scientific classification (Biology Wise, 2018).
Kingdom: Plantae
Phylum: Chlorophyta
Class: Chlorophyceae
Order: Volvocales
Family: Volvocaceae
Genus: Volvox
Reproduction
It takes place by both sexual and asexual manners. Basically, the colonies bear both
sexual (generative), as well as asexual (somatic) cells. The former ones get subdivided by the
process of mitosis to produce daughter cells. These cells are called gonads, which play a vital
role in asexual type of reproduction. The process of daughter cell formation continues till a tiny
invaginated daughter colony is formed. Flagella are formed in an inside-out manner, which
also means that the cells must get inverted into the spheres, way before they get released from
the parent family. The daughter colony is released only after the death of the parent colony
(Biology Wise, 2018).
Sexual reproduction of volvox is also called oogamous. Some of the generative cells
undergo the process of repeated cell division to produce sperm packets. These packets swim
along as a unit, and search for the ova (mature egg). These eggs only get developed by the
generative cells, which haven't undergone the stages of mitosis. After fertilization, the zygote
forms a red spiny cell wall, which is its resting stage, and meiosis takes place inside this
structure. Meiospores are formed during this resting stage of meiosis and produce new colonies.
The male and female volvox form separate germ cells, amongst which the latter ones get
enlarged, and do not divide. However, there are few species of this organism, which can
develop both sperm and ova, but at different times so that self-fertilization can be prevented
(Biology Wise, 2018).
Ecology
Volvox is free floating fresh water green algae. It grows as planktons on surface of water
bodies like temporary and permanent ponds, lakes and water tanks. The surface water becomes
green during rainy season due to its fast growth. The Volvox colonies appear as green rolling
balls on surface of water (Sharma, 2018).
Scientific Classification
Sargassum belongs to the following scientific classification (Biology Wise, 2018).
Domain: Eukaryota
Superphylum: Heterokonta
Class: Phaeophyceae
Order: Fucales
Family: Sargassaceae
Genus: Sargassum
Reproduction
It reproduces by both vegetative and sexual means. Asexual reproduction is absent
(Neelesh, 2018).
Vegetative Reproduction:
It takes place by fragmentation. Due to death and decay of the older part, the
younger region gets separated. The separated region grows and finally develops into a
new individual like the mother. The free-floating members like S. hystrix and S. natans,
multiply only by this method (Neelesh, 2018).
Sexual Reproduction:
It is of oogamous type and takes place by the union of antherozoid and egg,
developed in antheridia and oogonia respectively. The sex organs develop in separate
flask-shaped bodies the conceptacles, developed on branched receptacles. The
conceptales with antheridia or oogonia are called male or female conceptacles (Neelesh,
2018).
Ecology
The genus Sargassum is represented by about 150 species, and 16 of them can be found
in India. It is found in temperate, subtropical and tropical regions of both northern and southern
hemispheres. It is very common in Africa, South America, Australia etc (Neelesh, 2018).
In West Africa, a part of Atlantic Ocean becomes densely occupied by Sargassum and
the region is called as ‘Sargasso sea’. Sargassum filipendula, a free-floating large kelp found
in the Sargasso Sea, was discovered by Columbus in 1492, as the ships were held fast by the
sea weeds. In India it is found in Porbandar, Bombay, Okha, Lakshadweep Island etc (Neelesh,
2018).
Scientific Classification
Chlamydomonas belongs to the following scientific classification (Biology Wise,
2018).
(unranked): Viridiplantae
Division: Chlorophyta
Class: Chlorophyceae
Order: Chlamydomonadales
Family: Chlamydomonadaceae
Genus: Chlamydomonas
Reproduction
Both asexual and sexual reproductions occur in Chlamydomonas (Astitva, 2018).
Asexual reproduction takes place by the following methods:
Zoospore formation: Zoospores are formed when the conditions are favourable.
During the formation of zoospores, the cell becomes quiescent (nonmotile). Its flagella are
retracted or discarded. The contractile vacuoles disappear. Its protoplast divides longitudinally
into two. It is followed by a simultaneous division of each daughter protoplast and sometimes
by a third series of division. Each division of the protoplast is preceded by the division of the
nucleus into many parts. Thus, each cell produces 2-16 pieces. Each piece secretes a wall
around it and forms two flagella. Contractile vacuole and pigment spots also soon appear. In
this way 2-16 swarmspores or zoospores are formed within the parent cell. The zoospores or
swarmspores are liberated by gelatinization or by the rupturing of the patent cell wall. Each of
them develops into a new Chlamyclomonas plant. This process of division is repeated every
24 hours. Thus, by the end of week, from one parent plant about 2,000,000 individuals are
formed (Astitva, 2018).
Aplanospore formation: Aplanospores are formed under conditions of drought. The
zoospores instead of being liberated found up and develop into aplanospores. Aplanospores
germinate directly or divide to produce zoospores on the approach of favorable conditions
(Astitva, 2018).
Palmella stage: This stage is formed under less favorable, but not very dry conditions.
In this condition, the ponds are gradually drying up. So, the plants are growing on damp soil.
The daughter cells are produced by the division of the parent cells. These cells do not develop
flagella. They are embedded in the mucilage formed by the gelatinization of the parent cell
wall. The daughtei’cells divide further into four. Their cell walls also become mucilaginous.
Thus, a large number of small non-motile structures are formed. They are embedded in jellylike substance. In this way, an amorphous colony is formed. It has hundreds or thousands of
cells. All its cells are embedded in a common gelatinous matrix. This stage is known as
the palmella stage. It; s named so because the older phycologists thought it to be a species of
an alga named Palmella. This is, however, a temporary phase. Soon all small daughter cells
develop flagella and become motile. Sometimes, cells of the Palmella stage develop into thickwalled hypnospores. These are red colored due to the presence of a red pigment called
the haematochrome (Astitva, 2018).
Sexual reproduction
The sexual reproduction may be isogamy to anisogamy and oogamy. At the time of
sexual reproduction, the protoplast of a cell divides into 16,32 or even 64 biflagellate gametes.
The gametes may be naked called gymnogametes. Or they may be enclosed in a cell wall
called calyptogametes. The walls of calyptogametes may be left behind as the gametes fuse in
pair or they may be retained (Astitva, 2018).
I. Isogamy: In this case, the fusing pairs of gametes are naked and equal in size. It occurs
in Creinhardi and C.Iongistigma.
II. Anisogamy: In this case, fusing pairs are similar in shape but different in size. The female
cell produces four larger macrogametes. The male cell produces eight smaller microgametes. It
occurs in C.monocia, C. Braunii etc.
III. Oogamy: In this case, the fusing gametes are different both in size and shape Ooaamy
occurs in C. corcifera and C. gonium.
Ecology
Chlamydomonas has 150 species. It is the most common unicellular Volvocales. It is
one of the simplest unicellular widely distributed algae. It is found in standing water of ponds,
pools, ditches and on moist soil. It often grows in abundance in water rich in ammonium
compounds. The turbid green color of the water of the stagnant ponds is due to the presence of
thousands of these rants. Some of the species occur in very unusual places. In Chlamydomonas
ehrenbergi occurs in saline water. Some of its species are found in sea. A bright red pigment
is often abundant in certain species, especially in the resting stages. Such plants make the pools
red (Abida, 2018).
Reference
Abida. (2018). Type Chlamydomonas structure , occurrence & reproduction. Retrieved December 13,
2018, from Biology Boom: https://biologyboom.com/type-chlamydomonas-only-for-b-s/
Astitva, G. (2018). Chlamydomonas: Position, Occurrence and Structure (With Diagrams). Retrieved
December 13, 2018, from Biology Discussion: http://www.biologydiscussion.com/algae/lifecycle-of-chlamydomonas-with-diagram/53699
Biology Wise. (2018). Retrieved December 13, 2018, from Volvox Classification:
https://biologywise.com/volvox-classification
Neelesh, T. (2018). Sargassum: Occurrence, Features and Reproduction. Retrieved December 13,
2018,
from
Biology
Discussion:
http://www.biologydiscussion.com/algae/sargassum-
occurrence-features-and-reproduction/46977
Sharma, D. (2018). Volvox: Occurrence, Structure and Reproduction (With Diagrams). Retrieved
December 13, 2018, from Biology Discussion: http://www.biologydiscussion.com/algae/lifecycle-algae/volvox-occurrence-structure-and-reproduction-with-diagrams/21149
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