Pinnularia are elongated elliptical unicellular organisms. Their cell walls are composed chiefly of pectic substances on a rigid silica framework. Their walls are composed of two halves called thecae (or less formally, valves.) These halves overlap like a Petri dish and its cover.
What is raphe Pinnularia?
The raphe is wedge shaped in transverse section. It has circular thickening called central nodules in the centre. Similar thickening also present at the outer ends of raphe. These are called polar nodules. These nodules open to the external aqueous medium.
What is the function of Auxospore?
Auxospores typically play a role in growth processes, sexual reproduction or dormancy. Auxospores are involved in re-establishing the normal size in diatoms are successive mitotic cell divisions leads to a decrease in cell size.
What is an Epitheca?
Definition of epitheca
1 : an external calcareous layer investing the lower portion of the theca of many corals. 2 : the outer or upper half or valve of the diatom frustule — compare hypotheca.
What is the life cycle of Ectocarpus?
Like many brown algae, Ectocarpus has a haploid–diploid life cycle that involves alternation between two multicellular generations, the sporophyte and the gametophyte (Fig. 2; [10, 15]).
How do Chlamydomonas reproduce?
Chlamydomonas sexually reproduces through the involvement of two gametes: Isogamy: Both of the gametes that are produced are similar in shape, size and structure. These are morphologically similar but physiologically different. Also, Isogamy is most common in sexually reproducing Chlamydomonas.
What is Gongrosira stage?
Each part develops cysts or hypnospores. This stage of Vaucheria is called Gongrosira stage as it resembles the alga Gongrosira. The cyst ruptures in favourable conditions and protoplast comes out by amoeboid movement. This protoplast become spherical and secretes new wall. It germinates to form new filament.
What is Auxospore example?
: a reproductive cell in diatoms usually resulting from the union of two smaller cells or their contents and associated with rejuvenescence in cells that have become progressively smaller because of repeated divisions.
What are Auxospores and Hormogonia?
Auxospores and hormocysts are formed by several diatoms and a few cyanobacteria respectively. Bacillariophyceae members (diatoms) are microscopic, eukaryotic, unicellular or colonial coccoid algae. These algae are sexually reproduced by the formation of auxospores in most cases.
What is cyanobacteria Hormocyst?
Hormocysts are thick-walled hormogones, (two or more cells of trichomes) and are produced in somewhat drier conditions. While auxospres are found to occur in may diatoms, hormocysts are confined to a few cyanobacteria.
What is Epitheca and Hypotheca?
is that epitheca is (microbiology|planktology) the upper half of the theca of a thecate protist such as a diatom or dinoflagellate while hypotheca is (microbiology|planktology) the lower or posterior half of the theca of a thecate protist such as a diatom or dinoflagellate.
What is Epitheca in diatom?
An epitheca is the larger half of a frustule. The epitheca overlaps the hypotheca. In Greek epitheca means outer sheath.
What type of algae is Polysiphonia?
Polysiphonia is a genus of filamentous red algae with about 19 species on the coasts of the British Isles and about 200 species worldwide, including Crete in Greece, Antarctica and Greenland. Its members are known by a number of common names. It is in the order Ceramiales and family Rhodomelaceae.
What is the reserve food product of Ectocarpus?
The reserve food material is in form of laminarin and mannitol. The cell wall is differentiated into two layers, the inner firm layer is made of cellulose and the outer gelatinous layer contains alginic acid.
How do Chlamydomonas eat?
Chlamydomonas makes its food in the same way as green plants, but without the elaborate system of roots, stem and leaves of the higher plants. It is surrounded by water containing dissolved carbon dioxide and salts so that in the light, with the aid of its chloroplast, it can build up starch by photosynthesis.
What is Chlamydomonas made of?
Chlamydomonas | |
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Phylum: | Chlorophyta |
Class: | Chlorophyceae |
Order: | Chlamydomonadales |
Family: | Chlamydomonadaceae |
What is life cycle of Chlamydomonas?
(a) The sexual life cycle of Chlamydomonas reinhardtii consists primarily of four critical stages – gametogenesis, zygote formation, zygote maturation (zygospore formation), and meiosis (zygospore germination). … Zygotes will develop into zygospores with a thick cell wall, which is a dormant stage in the life cycle.
What is Synzoospore?
The zoospore of vaucheria is a compound structure which is formed by the failure of the protoplast within the zoosporangium to divide into uninucleate, biflagellate zoospore. It is also known as Synzoospore or conidiospores and these spores generally develop in aquatic forms of vaucheria.
What is Plakea stage?
The gonidium is separated from the vegetative cells by its position and size. Development of Daughter Colony: … The cells are arranged in such a pattern that their concave inner surface faces towards the outer side of the colony. This stage is called plakea stage or cruciate plate (Fig. 3.53D).
What is Palmella stage where it is found?
It is a genus of unicellular green algae (Chlorophyta). It is found in soil, stagnant water, and freshwater. Palmella stage is a type of asexual reproduction found in some algae such as mainly in Chlamydomonas, Euglena, etc.
What is Rejuvenescent cell?
Auxospores are also called as rejuvenescent cells as they form during cell division. Sporozoans have a complex life cycle. Sporozoans are the infective spores that can reproduce both by sexual and asexual mode. They are formerly placed in the class of sporozoa and also called as apicomplexans.
What is Statospore?
statospore (stat’-o-spore). A resting spore, e.g. a siliceous thick-walled resistant cyst formed within the frustules of various chiefly marine centric diatoms, and characterized by two overlapping convex valves and by absence of a girdle; or an intracellular cyst in various algae of the division Chrysophyta.
How are Auxospores formed?
The auxospores are formed by the fusion of two gametes, flagellated or not depending on the taxonomic group. Auxospores are swelled cells where a new cell wall of maximum dimensions is produced.
What is an Akinetes in biology?
An akinete is an enveloped, thick-walled, non-motile, dormant cell formed by filamentous, heterocyst-forming cyanobacteria under the order Nostocales and Stigonematales. … They also accumulate and store various essential material, both of which allows the akinete to serve as a survival structure for up to many years.
In which Hormogonia is the common method of reproduction?
Formation of hormogonia is the common method of reproduction in Nostoc which are produced by accidental breaking of trichome into several pieces. It may also be formed by death and decay of ordinary intercalary cells. Soon, the hormogonium escapes from mucilage and grows into a new filament and then into a new colony.
What are diatoms classified?
Diatoms are formally classified as belonging to the Division Chrysophyta, Class Bacillariophyceae. The Chrysophyta are algae which form endoplasmic cysts, store oils rather than starch, possess a bipartite cell wall and secrete silica at some stage of their life cycle.
What are hormogonia and akinetes?
Hormogonia are motile filaments of cells formed by some cyanobacteria in the order Nostocales and Stigonematales. They are formed during vegetative reproduction in unicellular, filamentous cyanobacteria, and some may contain heterocysts and akinetes. … This Cyanobacteria-related article is a stub.
Where is oscillatoria found?
It is commonly found in watering-troughs waters, and is mainly blue-green or brown-green. Oscillatoria is an organism that reproduces by fragmentation. Oscillatoria forms long filaments of cells which can break into fragments called hormogonia. The hormogonia can grow into a new, longer filament.
What is the difference between akinetes and Heterocyst?
Akinetes (Greek “akinetos”) are motionless, spore-like resting cells that differentiate from vegetative cells and serve in perennation. Akinetes are larger (sometimes up to 10-fold) than vegetative cells, and heterocysts possess thickened cell wall and a multilayered extracellular envelope (Adams and Duggan, 1999).
What is Epivalve and Hypovalve?
(a) The diatom is composed of an epitheca and hypotheca that fit together like a petri dish. Each theca is composed of the valve face (epivalve or hypovalve) and the valve mantle. … A cross section of the diatom reveals that the pores present on the external valve face penetrate to the internal face.
What are diatom Frustules made of?
The frustules, or cell walls, of diatoms are made of opaline silica and contain many fine pores. Large quantities of frustules are deposited in some ocean and lake sediments, and their fossilized remains are called diatomite.