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Also fruitless is any idea of improving upon their Prose. Enjoy!
 
Also fruitless is any idea of improving upon their Prose. Enjoy!
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==THE PROTISTS==
 
==THE PROTISTS==
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Their morphology may be unicellular, filamentous, colonial, or coenocytic, while some may have a plant-like structure. There are numerous transitions between the four types - algae, protozoa, fungi and the slime molds.
 
Their morphology may be unicellular, filamentous, colonial, or coenocytic, while some may have a plant-like structure. There are numerous transitions between the four types - algae, protozoa, fungi and the slime molds.
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== The ALGAE ==
 
== The ALGAE ==
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TABLE 26.1 Major Groups of Algae:  These are characterized by i) the Pigment System (chlorophylls or other special pigments), ii) the composition of the Cell wall, or iii) the nature of reserve materials; and they have the following Group Names - Green algae: division Chlorophyta - Euglenids: division Euglenophyta - Dinoflagellates and related forms: division Pyrrophyta - Chrysophytes and diatoms: division Chrysophyta - Brown algae: division Phaeophyta - and Red algae: division Rhodophyta.
 
TABLE 26.1 Major Groups of Algae:  These are characterized by i) the Pigment System (chlorophylls or other special pigments), ii) the composition of the Cell wall, or iii) the nature of reserve materials; and they have the following Group Names - Green algae: division Chlorophyta - Euglenids: division Euglenophyta - Dinoflagellates and related forms: division Pyrrophyta - Chrysophytes and diatoms: division Chrysophyta - Brown algae: division Phaeophyta - and Red algae: division Rhodophyta.
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== The Morphology of Algae ==  
 
== The Morphology of Algae ==  
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Verbally envisaging Figure 26.1 :  we are presented with a fixed Cell photomicrograph of Euglena gracilis X 1000 [courtesy of G. F. Leedale].
 
Verbally envisaging Figure 26.1 :  we are presented with a fixed Cell photomicrograph of Euglena gracilis X 1000 [courtesy of G. F. Leedale].
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== The Photosynthetic Flagellates==
 
== The Photosynthetic Flagellates==
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In many algal divisions, the simplest representatives are motile, unicellular organisms, known collectively as ''flagellates''. The Cell of a typical flagellate, illustrated by ''Euglena'' (Figure 26.1 - Euglena gracilis), has a very marked polarity: it is elongated and leaf-shaped, the flagella usually being inserted at the anterior end. In the Euglenophyta, to which ''Euglena'' belongs, there are two flagella of unequal length, which originate from a small cavity at the anterior end of the Cell. Many chloroplasts and mitochondria are dispersed throughout the cytoplasm. Near the base of the flagellar apparatus is a specialized organelle, the ''eyespot'', which is red, owing to its content of special carotenoid pigments; the eyespot serves as a photoreceptor to govern the direction and intensity of illumination. The Cell of ''Euglena'', unlike that of many other flagellates, is not enclosed within a rigid wall; its outer layer is an elastic ''pellicle'', which permits considerable changes in shape. Cell division occurs by ''longitudinal fission'' [Figure 26.2(a)]. About the time of the onset of mitosis, there is a duplication of the organelles of the Cell, including the flagella and their basal apparatus; cleavage subsequently occurs through the long axis, so that the duplicated organelles are equally partitioned between the two daughter Cells. This mode of Cell division is characteristic of all flagellates except those belonging to the Chlorophyta, such as ''Chlamydomonas'', where each Cell undergoes ''two or more multiple fissions'' to produce four smaller daughter Cells, liberated by rupture of the parental Cell wall [Figure 26.2(b)]. Even in such cases, however, the internal divisions take place in the longitudinal plane. As we shall see in a subsequent section, longitudinal division also occurs in the nonphotosynthetic flagellate protozoa and is one of the primary characters that distinguish these organisms from the other major group of protozoa that possess flagellalike locomotor organisms, the ciliates.
 
In many algal divisions, the simplest representatives are motile, unicellular organisms, known collectively as ''flagellates''. The Cell of a typical flagellate, illustrated by ''Euglena'' (Figure 26.1 - Euglena gracilis), has a very marked polarity: it is elongated and leaf-shaped, the flagella usually being inserted at the anterior end. In the Euglenophyta, to which ''Euglena'' belongs, there are two flagella of unequal length, which originate from a small cavity at the anterior end of the Cell. Many chloroplasts and mitochondria are dispersed throughout the cytoplasm. Near the base of the flagellar apparatus is a specialized organelle, the ''eyespot'', which is red, owing to its content of special carotenoid pigments; the eyespot serves as a photoreceptor to govern the direction and intensity of illumination. The Cell of ''Euglena'', unlike that of many other flagellates, is not enclosed within a rigid wall; its outer layer is an elastic ''pellicle'', which permits considerable changes in shape. Cell division occurs by ''longitudinal fission'' [Figure 26.2(a)]. About the time of the onset of mitosis, there is a duplication of the organelles of the Cell, including the flagella and their basal apparatus; cleavage subsequently occurs through the long axis, so that the duplicated organelles are equally partitioned between the two daughter Cells. This mode of Cell division is characteristic of all flagellates except those belonging to the Chlorophyta, such as ''Chlamydomonas'', where each Cell undergoes ''two or more multiple fissions'' to produce four smaller daughter Cells, liberated by rupture of the parental Cell wall [Figure 26.2(b)]. Even in such cases, however, the internal divisions take place in the longitudinal plane. As we shall see in a subsequent section, longitudinal division also occurs in the nonphotosynthetic flagellate protozoa and is one of the primary characters that distinguish these organisms from the other major group of protozoa that possess flagellalike locomotor organisms, the ciliates.
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== The Nonflagellate Unicellular Algae==
 
== The Nonflagellate Unicellular Algae==
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By no means are all unicellular algae flagellates; several algal divisions also contain unicellular members that are either immotile or possess other means of movement. Many of these unicellular and nonflagellate algae possess strikingly specialized and elaborate Cells, which may be illustrated by considering two groups, the ''desmids''  and the ''diatoms''.
 
By no means are all unicellular algae flagellates; several algal divisions also contain unicellular members that are either immotile or possess other means of movement. Many of these unicellular and nonflagellate algae possess strikingly specialized and elaborate Cells, which may be illustrated by considering two groups, the ''desmids''  and the ''diatoms''.
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== The Natural Distribution of Algae ==
 
== The Natural Distribution of Algae ==
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Most  algae are aquatic organisms that inhabit either fresh water or the Oceans. These aquatic forms are principally free-living, yet certain unicellular marine algae have established durable symbiotic relationships with specific marine invertebrate animals (e.g., sponges, corals, various groups of marine worms) and grow within the Cells of the host Animal. Some terrestrial algae grow in soil or on the bark of trees. Others have established symbiotic relationships with fungi, to produce the curious, two-membered natural associations termed ''lichens'', which form slowly growing colonies in many arid and inhospitable environments, notably on the surface of rocks.
 
Most  algae are aquatic organisms that inhabit either fresh water or the Oceans. These aquatic forms are principally free-living, yet certain unicellular marine algae have established durable symbiotic relationships with specific marine invertebrate animals (e.g., sponges, corals, various groups of marine worms) and grow within the Cells of the host Animal. Some terrestrial algae grow in soil or on the bark of trees. Others have established symbiotic relationships with fungi, to produce the curious, two-membered natural associations termed ''lichens'', which form slowly growing colonies in many arid and inhospitable environments, notably on the surface of rocks.
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== The Nutritional Versatility of Algae==
 
== The Nutritional Versatility of Algae==
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The ability to perform photosynthesis confers on many algae very simple nutrient requirements, in the light they can grow in a completely inorganic medium. However, many algae have specific vitamin requirements, a requirement for Vitamin B12 being particularly common. In Nature the source of these vitamins is probably bacteria that inhabit the same environment. The ability to perform Photosynthesis does not necessarily preclude the utilization of organic compounds as the principal source of carbon and energy, and many algae have a mixotrophic metabolism.
 
The ability to perform photosynthesis confers on many algae very simple nutrient requirements, in the light they can grow in a completely inorganic medium. However, many algae have specific vitamin requirements, a requirement for Vitamin B12 being particularly common. In Nature the source of these vitamins is probably bacteria that inhabit the same environment. The ability to perform Photosynthesis does not necessarily preclude the utilization of organic compounds as the principal source of carbon and energy, and many algae have a mixotrophic metabolism.
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Many algae that perform normal photosynthesis in the light, using CO2 as the carbon source, can grow well in the dark at the expense of a variety of organic compounds; such forms can thus shift from photosynthetic to respiratory metabolism, the shift being determined primarily by the presence or absence of light. Algae completely enclosed by Cell walls are osmotrophic and dependent on dissolved organic substrates as energy sources for dark growth. However, a considerable number of unicellular algae that lack a Cell wall, or are not completely enclosed by it, can phagocytize bacteria or other smaller microorganisms and thus employ a phagotrophic mode of nutrition as well. It is not correct, accordingly, to regard the algae as an ''exclusively'' photosynthetic group; on the contrary, many of their unicellular members possess and can use the nutritional  capacities characteristic of the two major subgroups of nonphotosynthetic eukaryotic protists, the protozoa and fungi.
 
Many algae that perform normal photosynthesis in the light, using CO2 as the carbon source, can grow well in the dark at the expense of a variety of organic compounds; such forms can thus shift from photosynthetic to respiratory metabolism, the shift being determined primarily by the presence or absence of light. Algae completely enclosed by Cell walls are osmotrophic and dependent on dissolved organic substrates as energy sources for dark growth. However, a considerable number of unicellular algae that lack a Cell wall, or are not completely enclosed by it, can phagocytize bacteria or other smaller microorganisms and thus employ a phagotrophic mode of nutrition as well. It is not correct, accordingly, to regard the algae as an ''exclusively'' photosynthetic group; on the contrary, many of their unicellular members possess and can use the nutritional  capacities characteristic of the two major subgroups of nonphotosynthetic eukaryotic protists, the protozoa and fungi.
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== The Leucophytic Algae== 
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== The Leucophytic Algae== 
      
Loss of the chloroplast from a eukaryotic Cell is an irreversible event, which results in a permanent loss of photosynthetic ability. Such a change appears to have taken place many times among unicellular algal groups with a mixotrophic nutrition, to yield nonpigmented counterparts, which can be clearly recognized on the basis of other Cellular characters as ''nonphotosynthetic derivatives of algae.'' Such organisms, known collectively as ''leucophytes,'' exist in many flagellate groups, in diatoms, and in nonmotile groups among the green algae. The recognition of leucophytes is often easy, since they may have preserved a virtually complete structural identity with a particular photosynthetic counterpart. In some case, this structural near-identity may include the preservation of vestigial, nonpigmented chloroplasts, as well as a pigmented eyespot. There can be little doubt accordingly that these non-photosynthetic organisms are the close relatives of their structural counterparts among the algae and have arisen from them by a loss of photosynthetic ability in the recent evolutionary past. Indeed, the transition can be demonstrated experimentally in certain strains of ''Euglena'', which yield stable, colorless races when treated with the antibiotic streptomycin or when exposed to small doses of ultraviolet irradiation or to high temperatures (Figure 26.7). These colorless races cannot be distinguished from the naturally occurring nonphotosynthetic euglenid flagellates of the genus ''Astasia''.
 
Loss of the chloroplast from a eukaryotic Cell is an irreversible event, which results in a permanent loss of photosynthetic ability. Such a change appears to have taken place many times among unicellular algal groups with a mixotrophic nutrition, to yield nonpigmented counterparts, which can be clearly recognized on the basis of other Cellular characters as ''nonphotosynthetic derivatives of algae.'' Such organisms, known collectively as ''leucophytes,'' exist in many flagellate groups, in diatoms, and in nonmotile groups among the green algae. The recognition of leucophytes is often easy, since they may have preserved a virtually complete structural identity with a particular photosynthetic counterpart. In some case, this structural near-identity may include the preservation of vestigial, nonpigmented chloroplasts, as well as a pigmented eyespot. There can be little doubt accordingly that these non-photosynthetic organisms are the close relatives of their structural counterparts among the algae and have arisen from them by a loss of photosynthetic ability in the recent evolutionary past. Indeed, the transition can be demonstrated experimentally in certain strains of ''Euglena'', which yield stable, colorless races when treated with the antibiotic streptomycin or when exposed to small doses of ultraviolet irradiation or to high temperatures (Figure 26.7). These colorless races cannot be distinguished from the naturally occurring nonphotosynthetic euglenid flagellates of the genus ''Astasia''.
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