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The asexual reproduction of the gametophytes takes place by neutral spores, monospores, and polyspores. placed. 3.120E). Phytoplankton • Diatoms • Silica impregnated, porous cell wall – Frustule - 2 halves • Asexual and sexual reproduction • Very rapid division = bloom. Grafting, layering, and micropropagation are some methods used for artificial asexual reproduction. 3.121D-H), while the oogoni­um still remains attached with the conceptacle. • Planktonic plant = Sargassum. The cortex is situated next to meristoderm and occupies major part of the axis. outside the ostiole by means of mucilaginous stalk. Internally it is almost alike with the axis but without medulla (Fig. oogonium is globular or ellipsoidal in outline. They are During development (Fig. Life Cycle Pattern. They attract a In sterile concep­tacle it only develops sterile hairs, the paraphyses, but in fertile conceptacle it develops either antheridia or oogonia and also paraphyses in some regions. Sexual reproduction may be isogamous, anisogamous or oogamous. in the free floating species of sargassum. The lower cell develops into rhizoid and the upper cell undergoes repeated periclinal and anticlinal divisions, thus forming a thalloid sporophyte (2n) of Sargassum. Pelagic Sargassum - ‘Gulf weed’ Class PhaeophyceaePelagic Brown Alga Drift alga Two holopelagic species, co-occur Occur in warm waters of Atlantic Ocean Asexual reproduction - The basal cell remains at the level of the fertile Reproduction The mode of reproduction is both sexual and asexual. Reproduction: o Vegetative reproduction: By fragmentation. 5. The main axis and primary laterals (long shoots) bear flat’ expanded structures, called secondary laterals or leaves. The protoplast of the oogonium then functions as a single Apical growth takes place by a three-sided apical cell. 8. egg elongates and divides into two cells. They ultimately get plced near the The plant body Sargassum is a diploid sporophyte. The mature antheridium (Fig. Reproduction of brown algae. Vegetative reproduction: Vegetative propagation takes place by fragmentation of the thalli. Sargassum reproduction is asexual, which means that every bit of the same species could probably be traced back to its original ancestor; therefore, some consider it the largest organism in the world! Reproduction in Sargassum: It reproduces by both vegetative and sexual means. body of Sagassum is a diploid sporophyte. Reproduction takes place by vegetative and sexual means. also termed as microsprangia and megasporangia. : A large number of antheridia develop in each male conceptacle. The plant flagella are inserted laterally. It has thick 3 layered To date, however, only S. polycystum is putatively known to propagate asexually. of motile sperm or male gamete with a nonmoile ovum or female gamete. 3.120C), then mitotic divisions and 8 nuclei are formed. 3.119C). Both kinds of sporangia are present on the same diploid sporophyte plant. Share Your PPT File. Chromatophore is reduced The difference lies in the activity of basal cells of the linear wall of conceptacle. Sexual reproduction occurs by a process known as conjugation, in which cells of two filaments lying side by side are joined by outgrowths called conjugation tubes. Due to rapid growth of the stalk cell, the antheridium becomes pushed at one side (Fig. The nuclei then accumulate some cytoplasm and form many uninucleate bodies. It is generally of circular in outline and differentiated into three regions: outer meristoderm, middle cortex and innermost medulla (Fig. 3.116). The oogonium is slowely extruded to the outside of theostiole. Each spore is germinated and liberated from the mother cell and gives rise to a new plant. 3.120A). The fertilized ovum has a diploid are borne on the lower branches of paraphyses. protoplast transforms itself into a single sperm or antherozoid. The diploid nucleus by the gelatinized wall of the oogonia and are held in position just The tongue cell elongates and gradu­ally disappears. The lower rhizoids which The mature The oogonial initial under­goes transverse division and forms lower small stalk cell and upper large oogonial cell (Fig. cell appears at the tip of the germling. Vegetative reproduction takes place by frag­mentation. Occurrence of Sargassum 2. Calculation of incidence of asexual vs. sexual dispersal is difficult as comparison with known asexually vs. sexually propagated populations of other Sargassum species within the same distribution range is needed. The sterile conceptacles are also called cryptoblast or cryptostomata. exchite, middle mesochite and inner endochite. It does not multiply asexually by means of spores. Life Cycle of Sargassum (With Diagram) | Phaeophyta, Anatomy of Sargassum (With Diagram) | Algae, Diatoms: Characteristics, Occurrence and Reproduction. In India it is found in Porbandar, Bombay, Okha, Lakshadweep Island etc. fragmentation which is the only known method of vegetative reproduction in the free floating species of Sargassum. Or they may be diploid formed in many­cellod plurilocular sporangia. 3.119B). The distinct genesis and blooming dynamics of the two seaweed species were detected and described. The diploid nucleus of the antheridial initial undergoes meiosis followed by repeated mitotic divisions forming 32-64 haploid nuclei. The wall of the oogonium consists of three layers, the outer exochite, the middle mesochite and inner endochite (Fig. The uppeer or antheridial 3.116). attach themselves to the gelatinous sheath of the ovm by mean of their The medulla i.e., the inner layer consists of narrow, thick walled elongated cells. The upper cell divide transversely at first. In … Like the outer layer this layer also stores food material. The oogonial cell becomes enlarged and forms a spherical structure. The sex organs develop in separate flask-shaped bodies the conceptacles, developed on branched receptacles. Reproduction in Sargassum The plant body of Sagassum is a diploid sporophyte. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. Vegetative Here's a list of organisms able to asexually reproduce. The diploid (2n) nucleus undergoes first meiotic (Fig. It is found in tem­perate, subtropical and tropical regions of both northern and southern hemispheres. sporic life cycle. An ecological demographic study was conducted from January to December 2009 at Changshan Island on the northern side of Shandong Peninsula, China. Plant Body of Sargassum 3. 3.117B). This process repeats sev­eral times and thus a branched structure is formed with lateral sporangia arranged alternately (Fig. layer. Here the wall dissolves and the sperms are released 3.119D). 3.122). In this article we will discuss about:- 1. while the functional haploid nucleus enlarges and becomes centrally It is of oogamous type and takes place by the union of antherozoid and egg, developed in antheridia and oogonia respectively. The fertilized are the various mechanisms of asexual reproduction. : Only a few oogonia are borne in a conceptacle. The lower one remains as concep­tacle Wall, whereas the upper one (Fig. Due to death and decay of the older part, the younger region gets separated. 3.119H). On the main axis as well as on the primary laterals, the secondary laterals i.e., the leaves are replaced by many spherical, hollow bodies, called air bladders. Internally the antheridium contains initially a of the conceptacle. The asexual reproduction is absent. The axils of leaves develop long much branched flattened or cylindrical structures called receptacles. They remain covered over The leaves are flat, simple structures with distinct midrib and dentate, serrate or entire margins, with an acute apex. The unicellular algae reproduce mainly by fission or cell division followed by separation of the individual cells. Some of the basal cells of the inner layer of conceptacle instead of forming oogonia remain sterile and form sterile, long, hair-like struc­tures, the paraphyses (Fig. In this process, some cells or protoplasm of few cells of the plant divide to create a small-sized structure, the spore. 10. Some examples are Ectocarpus, Dictyota, Laminaria, Sargassumand Fucus The cells are meristema- tic in nature. egg begins its germination while surrounded by the gelatinous sheath This process happens with the division and duplication of the parent’s genetic matter into two parts, here, each daughter cell receives one copy of its parent DNA. It is very common in Africa, South America, Australia etc. They Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and bacteria. 3.119F) is oval and covered by two walls, outer firm exochite and inner gelatinous endochite. The cells contain chromatophores and perform photosynthesis. The holdfast is discoid and serves the func­tion of anchorage with the substratum. towards maturity. 3. Asexual reproduction occurs by forming a specific type of spores. One of The wall of the mature antheridium After liberation, the zygote gets attached with any solid substratum. Sargassum shows diplontic life cycle without any alternation of generations (Fig. The central region is occupied by a large hollow cavity filled with air and gases. These dots are the ostioles i.e., openings of the sterile conceptactes. It takes place by fragmentation. Sargassum fiends usually reach sizes up to 10 feet in diameter before splitting, their means of asexual reproduction. (With Methods)| Industrial Microbiology, How is Cheese Made Step by Step: Principles, Production and Process, Enzyme Production and Purification: Extraction & Separation Methods | Industrial Microbiology, Fermentation of Olives: Process, Control, Problems, Abnormalities and Developments, The best answers are voted up and rise to the top. It breaks its connection from the paraphysis 3.119A). The study investigated stem regeneration and the resource trade-off between sexual reproduction and vegetative regeneration of the brown alga Sargassum thunbergii at the individual thallus level. The cells of the wall have many chromatophores. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. 3.119C). It produces the typical thallus. In case of the sexual type, two haploid sex cells are fused to form a diploid zygote that develops into an organism. shorter flagellum is of tinsel type while the posterior longer flagellum The primary branch gives rise to secondary branches which are rod-like in structure. Share Your Word File The antheridial cell develops into an antheridium (Fig. Most of the species of Fucales reproduce sexually except Sargassum natans and Sargassum fluitans, which reproduce only by fragmentation (Lee, 2008). What is its function? Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes.The offspring that arise by asexual reproduction from a single cell or from a multicellular organism inherit the genes of that parent. The plant body Sargassum is … The thallus breaks into fragments due to mechanical injury or death and decay of older parts. 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. is a pear shaped biflagellate structure of pale brown colour. usually bears only one type of sex organs. Many antherozoids get attached with the egg by their anterior flagella and their posterior ones help in swimming (Fig. : The ova of sargassum are not shed in sea. Name the types of nitrogenous bases present in the RNA. Oogonium produces one egg and the anthe­ridium produces 64 biflagellate sperms. The mature oogonia come out of the conceptacle through the ostiole, but still they remain attached with the conceptacle base by a long gelatinous stalk formed by the exochite. becomes mucilaginous. TOS4. A sperm Like antheri­dium, oogonium also develops from the basal fertile layer of the conceptacle (Fig. The diploid nucleus undergoes meiosis and an upper oogonial cell. Our mission is to provide an online platform to help students to share notes in Biology. When two or more separate multicellular algae stages occurs in succession during the life cycle, we call this: alternation of generations. In addition to vegetative reproduction by fragmentation of the thallus most brown algae reproduce both by asexual and sexual means. The basal cell, then undergoes repeated vertical divisions to form the basal fer­tile layer i.e., the inner layer of the conceptacle. This cell is larger in size with dense protoplasm than the other surrounding cells. In the … 3.118B). This process is primarily found among plants, microorganisms, insects and reptiles. 13. is ovoid in outline. After formation of … single diploid nucleus and a few chromatophores. The phylum of green algae is: Chlorophyta. The remaining antherozoids get separated and gradually dege­nerate, Initially after fertilisation both the nuclei remain side by side (Fig. of the conceptace by means of mucilage stalk. derived from the oogonial wall and still attached to the interior Sexual reproduction is very common and can be isogamous (gametes both motile and same size), anisogamous (they are both motile and are of varied sizes–female is bigger), or oogamous (female non-motile and egg-like and male motile). The air bladders help to float them in water (Fig. The species is monoecious, i.e. Privacy Policy3. cell develops into an antheridium. The conceptacles bear sex organs. 3.119A) again divides transversely and forms a lower stalk cell and an upper antheridial cell (Fig. Any cell of the fertile layer can function as 3.117D). 11. Thus it shows a typical example of diplontic life cycle. 3.118A). Fragmentation is a type of ___ for drift algae, like Sargassum. What is a mushroom shaped gland? 3.120F). gelatinous sheath dissolves and the fertilised eg in its early stage o Asexual reproduction: By pear-shaped biflagellate zoospores (have 2 unequal laterally attached flagella). of the antheidium get divided into 64 haploid protoplasts. Asexual reproduction is absent. 7 of them usually degenerate The monospores are developed in sporangia. The stalk cell again undergoes transverse division and forms upper antheridial cell and lower stalk cell. Reproduction. 64 sperm develop inside an antheridium. Instead it reproduce by vegetative means, i.e. The thallus is differentiated into a basal holdfast and an expanded, leafy, cylindrical main axis. An unprecedented bi-macroalgal bloom caused by Ulva prolifera and Sargassum horneri occurred from spring to summer of 2017 in the western Yellow Sea (YS) of China, where annual large-scale green tides have prevailed for a decade. The surrounding cells of the conceptacle initial divide rapidly and push it towards the inner side of the receptacle. 3) Primary and secondary branches: Many primary and secondary branches grow from the stipe which is more or less similar to leaf in structure, called primary branches. 3.120C). Simultaneously a three side apical The zygote is diploid (2n) and on germination it develops sporophytic (2n) plant of Sargassum. Disclaimer Copyright, Share Your Knowledge by means of spores. 4. The middle wall layer What are the general characters of bryophytes? These are flask-shaped with many sterile unbranched filaments, the paraphyses developed from the base. The first antheridium 3.121A). 3.120D) which remains in the centres. Asexual reproduction is either by biflagellate zoospores or by non-flagellate tetraspores developed in sporangia. 3.121 B), but later they fuse together and form the zygote (Fig. It reproduces by both vegetative and sexual means. These zoospores may be haploid produced in one-celled unilocular sporangia. 6. The antherozoids and eggs i.e., the gametes, represent only the haploid (n) stage. if of whiplash type. It does not multiply asexually The nucleus is larger. This type of reproduction is the result of the body´s fragmentation, which occurs due to exposure to unfavorable environmental conditions or as a part of the normal life cycle. 3.117C). Asexual reproduction is absent. inside special cavity called conceptacles. Mutations have been known to exist, however, and sea-faring scholars have recorded individual sargassum fiends reaching masses of truly enormous size, up to Colossal. Oogonia (A) Vegetative Reproduction in Sargassum: Sargassum multiplies profusely by vegetative fragmentation. This layer can store food material. Sometimes, the leaves growing towards sun­light show many dots on both the surfaces. The macroalgae genus Sargassum adopts a heteromorphic life history (distinct sexual haploid and asexual diploid stages) and oogamous fertilisation (union of mobile male and immobile female gametes) [ … reproduction : FRagmentation is the only known method of reproduction Fertlization The reproduction of the sea sponges can be asexual or sexual. The neutral spores develop in ordinary cells of thallus, e.g., Asterocystis. and posses an eye spot. It consists of compactly arranged parenchyma cells of poly­gonal shape, rarely with intercellular spaces. Out of these, 7 nuclei degenerate and the remaining one functions as an egg (Fig. Some of the cells of this layer function as an oogonial initials (Fig. Internal Structure 4. It has a thick wall which becomes mucilaginous Asexual reproduction is a reproductive process devoid of gamete formation and fertilization, and mostly proceeds via mitosis. Instead it reproduce by vegetative method and Zygote germinates directly and produces a new sporophytic (2n) plant. The uninucleate bodies metamorphose into pyriform, haploid biflagellate antherozoids (Fig. The algae are free floating and brown in colour, commonly found in tropical seas, though some are found in Sargasso Sea (a region of North Atlantic Ocean). alternation of generations between gametophyte and sporophyte ... 99.7% of species are marine, mostly benthic (sargassum - not benthic) Olive-brown color comes form the carotenoid pigment fucoxanthin. The former type refers to reproduction in which a new organism is generated from a single parent. It is erect, flattened or cylindrical structure. In this method of asexual reproduction, there is a separation of the parent cell into two new daughter cells. The resultant offspring is a clone of the parent organism due to the absence of genetic exchange. nuclei in one to one ratio. Antheridia The genus Sargassum (Spanish sargazo, sea­weed) is represented by about 150 species, out of which 1 6 species are found in India. The main axis bears many primary laterals arranged spi­rally in a phyllotaxy of 2/5. climate Sargassum muticum has been shown to grow year round, but it will still lose its branches (Norton, 1976; Arenas & Fernández, 2000; and Britton-Simmons, 2004). Asexual, or vegetative, reproduction occurs by simple fragmentation of the filaments. What is the significance of transpiration? oogonial initial. Welcome to BiologyDiscussion! 1. the conceptacles are found The conceptales with antheridia or oogonia are called male or female conceptacles. The other sperm swim away. Asexual reproduction simply means an individual produces another of its kind all on its own, without exchanging genes with another organism through sex. Asexually reproducing plants thrive well in stable environments. The medulla is round and present in the middle region. the sperm penentrate the mucilaginous covering and fuses with the The main axis i.e., stem is vertically elonga­ted and differentiated into nodes and inter­nodes. It bears long shoots of unlimited growth (primary laterals), leaves (secondary late­rals), air bladders and receptacles. The meristoderm is made up of single layer of closely packed cells. 3.119D, E). The new plant is genetically identical to the parent plant from which the stock has been taken. Thus the thallus shows division of labour along with differentiation of tissues. Where are the pollen grains formed in the flower? Phytoplankton • Diatoms • Ecology – Thrive in cold, nutrient rich waters – 2 growth forms = centric & pennate • Centric = best floater Asexual reproduction. The receptacle bears many fertile flask-shaped structures, the conceptacles. nucleus and is called zygote. 3.117A). 7. The three wall layers are outer 3.120). The conceptacle ini­tial then undergoes mitotic division and by oblique septation it forms upper elongated tongue cell and lower broad basal cell (Fig. and mitosis to produce 8 haploid nuclei. Following are the artificial methods of asexual reproduction in plants: Cutting. Due to its unlimited growth, the primary laterals are also called long shoots. of meristoderm cortex and medulla. Instead it reproduce by vegetative method … It serves the function of anchorage, photosynthesis, storage, conduction and support. They are respectively borne inside antheridia and oogonia. Just after fertilization the zygote undergoes germination (Fig. It divides transveresly into a lower stalk cell 2. Asexual reproduction is absent. of germination falls down on some solid substratum. Asexual reproduction is by fission, budding, fragmentation or by zoospores (motile spores). Later on only one penetrates the oogonial wall. Union of gametes occurs in water or … The ctoplasm cleaves and the contents Thus It however remains attached to its original position by means of a The lower basal cells of the conceptacle are the antheridial initials forming papilla like outgrowths (Fig. inside the sporangia to produce gametes. Some common brown algae : A. Sargassum; B. Fucus. Artificial Methods. The plant body is diploid (2n), erect and branched thallus (Fig. At maturity the antheridium is detached from the stalk and comes out from the conceptacle through ostiole. asexual reproduction in which the thallus breaks up into pieces, which grow into new algae. divides meiotically and then mitotically to form 64 haploid nuclei. In the higher form of algae, in addition to vegetative reproduction i.e., by separation of parts of the individual (fragmentation) both asexual and sexual reproduction in algae is common. and a number of oil droplets. The conceptacles ovum. Let’s discuss in brief about the vegetative, asexual, and sexual reproduction in algae along with examples. Outer to the cavity, cortex is present; which consists of a few layers and thinner cells than axis and finally it ends with a single layered outer meristoderm. It generally takes place by the following method: Share Your PDF File It does not multiply asexually by means of spores. Each one divides by a transverse wall into two cells. from the cells of the fertile layer, very early in the development inside small finger-like branchlets called receptacles. The most frequent type of asexual reproduction is by budding. Thus con­ceptacle contains oogonia intermingled with paraphyses. It swelling breaks They are unequal in size. Development of conceptacle. Sargassum muticum is a monoiceisus alga that can reproduce through both sexual and asexual reproduction; it also possesses a reproductive The later become esptate. Reproduction 7. the formation of sex organs. anterior flagella. is borne at the tip of a 3-celled filament which arises from a cell Each such the exochite. This is a dioecious species producing separate male and female colonies. and comes out. The main axis is generally of 10 to 50 cm in length. The plant body is diploid and differentiated into root, stem and leaf-like structures. The macroalgae genus Sargassum adopts a heteromorphic life history (distinct sexual haploid and asexual diploid stages) and oogamous fertilisation (union of mobile male and immobile female gametes) . Union of gametes may take place in water or within the oogonium (oogamous species). 1. The cells are smaller in size than meristoderm. 3.119). then shows differntiation of outer and inner cells, followed by disiction The spores germinate The free floating members like S. hystrix and 5. natans, multiply only by this method. On both surfaces of the leaf there are many sterile conceptacles, the cryptostomata or cryptoblasts (Fig. Botany, Algae, Phylum Heterokontophyta, Classes, Phaeophyceae, Sargassum. 3.120B). The anterior of the fertile layer. Both stem and leaves are differentiated into epidermis, cortex and medulla. The asexual reproduction takes place by the formation of biflagellate zompores. reproduction : The reproduction is oogamous and involves the fusion 3.121C). Which organelle is known as “power house” of the cell? The young oogonium contains a conspicuous diploid nucleus, dense cytoplasma It is flat and differentiated into outer meristoderm, middle cortex and inner medulla like the axis (Fig. After some time it comes out of the gelatinous wall. After some time the Reproduction takes place by vegetative and sexual means.

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