Here is a compilation of term papers on ‘Amoeba’. Find paragraphs, long and short term papers on ‘Amoeba’ especially written for college and medical students.
Term Paper on Amoeba
Term Paper Contents:
- Term Paper on the Introduction to Amoeba
- Term Paper on the Habits and Culture of Amoeba
- Term Paper on the Locomotion of Amoeba
- Term Paper on the Respiration and Excretion in Amoeba
- Term Paper on the Osmoregulation in Amoeba
- Term Paper on the Behaviour of Amoeba
- Term Paper on the Economic Importance of Amoeba
Term Paper # 1. Introduction to Amoeba:
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Amoeba of fresh water ponds and ditches, etc. is a simple-looking microscopic animal. It is difficult to study it the way other animals are studied because all the capacities that large animals delegate to their different organs are inextricably mixed up in a shapeless arid almost structure less drop of protoplasm. Amoeba was discovered by Russel von Rosenhoff in 1755. He called it “the little proteus” after the mythical sea god who is believed to be capable of changing shape.
Amoeba proteus (Gr., amoibe = change) is commonest and best-known protozoan. Other common species are A. radiosa. A. discoides. and A. verrucosa. Amoeba can be made available for study from places like organic ooze from decaying vegetation or lower surface of lily pads.
Term Paper # 2.
Habits and Culture of Amoeba:
Habits:
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It is a minute and free-living form commonly found in the ooze or bottom-mud in freshwater ponds, ditches, lakes and spring-pools containing bacteria and organic substances, such as leaves, twigs and other aquatic vegetation in abundance. The sides of lotus ponds and the water troughs are good places to collect them. They move so slowly that only a trained eye can discern movement.
Culture:
Amoeba may be obtained for class work by scraping decaying vegetation from the bottom of a pond. When the scraping is allowed to settle in a wide mouth container, amoebae of different kinds may be found in the sediment and sorted with the help of a fine pipette under a binocular microscope.
Amoeba can be cultured in laboratory. Place some pond water, mud and leaves in 100 ml of water containing a few grains of wheat. Amoebae will appear after a few days. To make a pure culture, boil 4 or 5 grains of wheat in 100 ml of distilled water for 10 minutes and cool for a few days. To this add some amoebae from the previous culture and cover with glass plate. Within 10 days, many more amoebae will appear in this culture.
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Term Paper # 3.
Locomotion of Amoeba:
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The locomotion of the Amoeba is affected by the formation of temporary finger-like processes or pseudopodia. Amoeba have no distinct head or tail ends but have a surface which is everywhere the same, and any one point on this surface may flow out as a pseudopod. The protoplasm that enters into it is withdrawn from other parts of the body, and therefore, if the formation of pseudopods is mainly in one direction the amoeba moves to that side.
But sooner or later another similar pseudopod forms at an adjacent point and the cytoplasm flows into it. In this manner the animal progresses in an irregular fashion, new pseudopods appear the old ones flow back in the general mass. Such movements are known as ‘amoeboid movements’. Amoeboid movements are very slow, and the animal does not proceed for long in any one direction.
The pseudopodia of Amoeba are known as lobopodia due to their blunt, finger-like appearance and rounded tips. The lobopodia may be of the profluent or of eruptive type according to their mode of formation. In the profluent type, the ectoplasm forms a bulging which gradually grows bigger as the endoplasm flows into it.
The profluent pseudopodia may be further distinguished into the lobose or multipodal type, i.e., several of them formed together (e.g., A. proteus) or into limax or monopodial type, when a single large one is formed (e.g. A. limax). In case of eruptive type, the surface breaks at a weaker point, so that the ectoplasm and the endoplasm flow out explosively to form the pseudopodia. Eruptive pseudopodis are met with only in smaller forms and formed usually single.
Amoeboid movement occurs in other Protozoa, and also in the amoebocytes of sponges and in white blood corpuscles of the vertebrates. Amoeboid movement has always excited great interest because it is presumed to be one of the most primitive types of animal locomotion.
Apparently it is totally different from the muscular movement of complex animals. But it is probable that a thorough understanding of the mechanism of amoeboid movement may throw some light on the general nature of contractility and thus elucidate the nature of muscle contraction.
Speculation about amoeboid movement goes back a hundred and thirty years to Ehrenberg, who first suggested that pseudopodia were hernia-like protrusions forced out by muscular contractions of hind part of the animal. Within a year, the alternative view was put forward that the pseudopodia were themselves inherently extensible, and pulled the rest of the animal after them, and ever since biologists have held essentially one or the other of these views.
Amoeba crawls about 0.02 to 0.03 mm. per minute. A pseudopodium can form at any point on body surface. It first appears as a small fingerlike bulge of homogenous glistening fluid, called “hyaline cap”. As the bulge touches a substratum, there is a sudden rush of granular endoplasm into it.
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The bulge therefore elongates and becomes a pseudopodium. In A. proteus, several pseudopodia usually begin to form simultaneously in different directions, but only one ultimately elongates; all others are withdrawn back into the body. Consequently, there is some displacement of body in the direction of the completed pseudopodium.
Soon, a new pseudopodium similarly forms elsewhere and the organism, therefore, moves in a different direction. The movement is, thus, quite erratic and never in the same direction for long.
Term Paper # 4.
Respiration and Excretion in Amoeba:
Like other animals, amoeba needs energy for its vital activities, and obtains it by oxidative breakdown of “fuel compounds”. Oxygen (O2) required for this is obtained, in solution, from surrounding water. Similarly, CO2, formed as a by-product of oxidation, also leaves the body in solution.
This gaseous exchange occurs through the plasmalemma by diffusion in accordance with diffusion gradients. Due to active metabolism, concentration of O2 is always lower and that of CO2 always higher in the cytoplasm than in surrounding water. Hence, O2 continuously enters into the body and CO2 leaves it in exchange.
As in other cells, a metabolic cycle of chemical reactions ceaselessly continues in amoeba for growth and energy-production. Different proteins are synthesized from amino acids under genetic control for growth and repair, and for acting as enzymes for metabolic reactions. Fats are synthesized from fatty acids and glycerol for growth and storage.
Sugars are oxidized to release energy which is stored in ATP molecules within mitochondria. In cytoplasm, ATP molecules are degraded into ADP to release their biologically usable energy.
During the process of respiration, the burning of proteins yields not only carbon dioxide and water but also nitrogenous wastes which are poisonous and must be passed out of the body. These wastes include ammonia compounds and sometimes urea. These are soluble and are also passed out of the body by diffusion or through the contractile vacuole. This process of elimination of nitrogenous waste is called excretion.
Term Paper # 5.
Osmoregulation in Amoeba:
The contractile vacuole is a mechanism for osmoregulation, i.e. control of water content of the cytoplasm. When perfectly formed a contractile vacuole is a spherical cavity containing liquid.
It appears as a clear circular area in the cytoplasm, slowly increases in size by the collection of more liquid in it and finally contracts suddenly discharging its contents to the exterior. Soon it appears again from one or more minute droplets, grows in size, as before, until it collapses again.
From this it is evident that some liquid is collected in it and expelled from the cytoplasm periodically through a temporary pore on the surface. The growing phase up to the maximum size reached is called diastole, and the collapsed condition is referred to as systole.
The water comes in the animal body mainly from three sources:
a. It is produced as a result of respiration;
b. It may be included when food particles are engulfed, and
c. It may enter osmotically through the semipermeable membrane, the plasmalemma.
Thus, there is a continual influx of water which may lead to the rupture of the animal if not expelled.
It is this excess of water that is collected in the contractile vacuole and expelled periodically. How the water is forced out of the protoplasm into the vacuole is not exactly known. There are three theories describing growth of the contractile vacuole. These include the osmotic theory, the filtration theory and the secretion theory of the diastole.
According to the first the water passes into the growing vacuole by the simple process of osmosis. According to the second (filtration theory) the water filters through the vacuolar membrane into the vacuole because of the hydrostatic pressure of the endoplasm. The third (secretion theory) suggests that the water is first absorbed by the vacuolar membrane and then secreted into the vacuole.
It has been recently found out in A. proteus that the growth of the vacuole takes place in spurts and not steadily. From this it is inferred that the fluid enters the vacuole by the fusion of similar smaller vacuoles.
On attaining maximum size the vacuole migrates to the surface until it reaches the plasma-membrane, which subsequently bursts discharging the contents. The location of the vacuole is not definite is such forms and it moves about with the cytoplasmic movements. As a rule it is confined to the temporary posterior region of the body.
It is possible that the expelled water may contain some excretory products, but there is no experimental evidence to show that the vacuole serves as an excretory organ. On the other hand, there is evidence against the excretory role of the contractile vacuole. Marine animals of similar constitution to Amoeba do not possess a contractile vacuole and yet excrete.
Besides, experimentally increasing the concentration of salts in the water surrounding the amoeba causes the vacuole to contract less and less frequently and finally to vanish altogether. Conversely, some marine relatives of amoebae develop contractile vacuoles when placed in fresh water.
It is, therefore, concluded that the chief function of the contractile vacuole is to regulate the water content of the amoeba. In the parasitic protozoa with contractile vacuoles, most of the water expelled probably enters in the feeding process.
Term Paper # 6.
Behaviour of Amoeba:
Amoeba responds to both external and internal stimuli, i.e. it is sensitive to touch, or nearness of food, or some other influence. Responses of an amoeba to stimuli constitute behaviour, the old word for which is irritability. There are many different types of external stimuli to which an amoeba reacts and the nature of the reaction depends upon the intensity of the stimulus.
A response involves the entire body of the animal, which either moves away from the stimulus (negative-response) or continues moving towards it (positive response). Hunger on the other hand is internal stimulus response to which an amoeba searches food.
Term Paper # 7.
Economic Importance of Amoeba:
(a) Basic Uniformity of Structure and Function from Lowest, to the Highest Animals:
A metazoan body is formed of numerous cells, and each cell is a tiny mass of protoplasm like an amoeba. Obviously, there is no difference in the basic structure of body from lowest to highest types of animals; the difference is only in their body organization.
If a cell is separated from a metazoan body, it will fail to remain alive and will soon die and disintegrate. On the contrary, the single cell, constituting the body of an amoeba, is so organized as to lead a free life; it is an unspecialized, “omnipotent cell”. Vital activities of amoeba further prove a basic similarity of function or physiology in all animals.
The peripheral cytoplasmic layer of each daughter amoeba changes into a tough and resistant spore-membrane. The residual cytoplasm of parent body, probably laden with excretory crystals, disintegrates, releasing spores in water. The spores sink down at bottom of the ponds. On, return of favourable conditions, their spore-membranes rupture. Thus, a minute amoeba emerges out from each pore and rapidly grows into an adult amoeba.
Regeneration:
Amoeba has great powers of regeneration. If an individual is cut into two or more pieces, accidentally or in the laboratory, then every piece containing a part of nucleus will subsequently grow into a complete Amoeba. A piece without a nuclear fragment degenerates and dies off. Although regeneration is not a reproductive process, yet it also helps in the multiplication of the animalcule.
Conjugation:
Some observers have described a temporary fusion between two amoebae. After some time they become separated again. It is said that this temporary union enables the two amoebae to lead a more active and vigorous life. This phenomenon is termed conjugation or rejuvenation.
According to Catkins a method of reproduction in A. proteus, in which gametes are formed which fuse in pairs to form the zygotes. However, the fusion of gametes or adults has not been confirmed by other observers and is doubtful.
(b) Basic Irritability of Protoplasm:
Amoeba has no special arrangement for sensory reception and reactivity (= responses). Yet it gets stimulated by environmental conditions and responds according to them. Obviously, amoeba demonstrates that irritability is a basic property of protoplasm.
(c) Immortality of Amoeba:
Weismann explained that a multicellular animal body is divisible into 2 parts—somatic and germinal. The somatic part or “soma” is the vegetative part, concerned merely within the maintenance of body itself.
Owing to continuous wear and tear, it stops functioning after a certain age. Thus, it is mortal and lasts only up to death of the organism. The germinal part or ‘germ’ is, on the other hand, concerned with reproduction; at least some part of it is transferred to the progeny before death of the organism. It is, therefore, immortal.
The body of Amoeba is not divisible into soma and germ. Hence the whole body gets divided into two daughter amoebae in binary fission, and into many small daughters in sporulation and multiple fission. Although the parent amoeba loses its identity in these processes, i.e., does not exist thereafter, but no part of its body has been wasted or destroyed. The daughter amoebae, thus formed, grow to optimum size and repeat the process.