Amoeba is a single celled animal belonging to amoeba of Proteomorpha family.[5-6]There is only a thin plasma membrane on the surface of the body, with transparent cytoplasm inside, which can be clearly divided into two parts: endoplasmic and exoplasmic;Pseudopods are finger like, leaf like or needle like;The insect body can carry out special deformation movement through the pseudopodium, which changes with the expansion and contraction of the pseudopodium;In addition to the movement function, pseudopodia also has the function of feeding. After wrapping food, it undergoes intracellular digestion.[7]It is named because the insect body flows with the protoplasm and its body shape often changes.
Amoebas are widely distributed, with thousands of species.Usually living in sewage, pond or wet soil,[8]In addition, there are many kinds of symbiosis or parasitism in humans and higher animals.[9]The ability to resist hunger is extremely strong. When food is exhausted, it will be attracted by the chemical distress signals released by the same kind, and will gather together to form a tiny flowing "slug".[10]The mode of reproduction is mitosis.
Amoeba is one of the lowest primitive creatures, with simple structure and easy cultivation. It is one of the main materials for life science experiments,[7]It can also be used as an indicator animal to determine the degree of water pollution.[8]
invertebrate，Protozoa, Carnopoda, amoebaceae.There is no tough surface membrane on the body surface, only a thin plasma membrane.Inside the membrane are relatively transparent cytoplasm, which can be clearly divided into two parts, namely, endoplasmic and ectoplasmic.Endoplasm can also be divided into immovable gelatine and lysosome that can flow with the movement of the insect body.The protoplasm can flow in any direction around the cells, resulting in amorphous protuberances on the body surface, called pseudopods.Pseudopods are finger like, leaf like or needle like.The insect body can carry out special deformation movement through the pseudopodium, which changes with the expansion and contraction of the pseudopodium.In addition to the movement function, pseudopodia also has the function of feeding. After the pseudopodia wraps the foodIntracellular digestion。Due to the flow of cytoplasm, one or more temporary, amorphous finger like, leaf like or needle like protuberances can be generated on the body surface, which are called pseudopods. The body moves forward on this basis.The contour of the body changes with the expansion and contraction of the pseudopodium.Pseudopodia can also surround trichomonas, diatoms, bacteria and other foreign substances and water together to form food bubbles as food, and digest the wrapped food.Indigestible residues (such as diatom shells) can be discharged from any part of the plasma membrane.There are many kinds.Generally, they live in fresh water ponds, paddy fields or still water ditches with many algae. Amoebaproteus can often be found under water, in sapropel or on the water surface. The diameter of the insect body can reach more than 200 microns, which can be seen by the naked eye.When observing under the microscope, do not shake, otherwise, it will be difficult to find if it shrinks into small balls.There is an oval nucleus in the cytoplasm. After staining with methyl acetate green, one contractile bubble can be seen.The insect body reproduces in a dichotomous manner.[1]
Origin of name
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Diagram of amoeba movement
The amoeba is named because it can change its shape, which is promoted by microfilaments in the cytoplasm, which exist in eukaryotesCell plasma membraneIn the thin layer below, it is a part of microtubule system.
Growth environment
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Mitogenesis of amoeba
The amoeba mainly lives in clear water ponds, or in shallow water with slow flow and more algae. It can also be found in general soil, orparasiteParasitic in other organisms.
Take water from a pond with water plants (preferablyGreen pondOrganic matter), together with aquatic plants and decaying stems and leaves.Place the pool water and water plants in a place without sunshine for 3-5 days, and yellow foam will emerge on the liquid surface. At this time, amoebas can be found from the foam.
Form and life
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Food ingestion by amoebas
The body of an amoeba consists of only one cell and has no fixed shape. It can change its shape at will.At the same time, amoebas can also extend pseudopods all over the body, whose main functions are movement andFeeding。They are generally based onunicellularAlgae and small unicellular animals are used as food.When encountering food, amoebas will stretch out pseudopods to surround them and digest by the food bubbles in the cytoplasm.There areTelescopic bubbleandFood bubbleThe function of expansion bubble is to remove excessive water in amoeba, while the function of food bubble is to digest food nutrients.The digested food will enter the surrounding cytoplasm;The indigestible substances will be discharged from the body through the plasma membrane, which is called excretion.The amoeba wraps up its prey through pseudopods to produce a food bubble, and then the food bubble fuses with the primary lysosome in its cell to form a secondarylysosome, digest the food.Large amoeba can swallowparamecium。Amoebas, like other organisms, need energy for respiration.During the respiration of amoeba, the oxygen inhaled and the oxygen excretedcarbon dioxideThe cell membrane is responsible for this.The mode of reproduction is also quite simple, mainly relying on mitosis, that is, the original genetic material is copied first, and then divided into two together with the whole cell;The nucleus is responsible for genetic function, just like other organisms.[2]
Amoeba magna
effect
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Amoeba is one of the lowest primitive creaturesUnicellular animal。Living conditions are the same as multicellular organisms.Due to the simple structure and easy cultivation of amoebalife sciencesOne of the main materials of the experiment.
There are many kinds of amoeba in this family.For example, foraminifera, noctiluca and radiolaria live in sea water, heliothis and amoeba live in fresh water, and plasmodiumAmoeba dysenteriae。In dysentery, amoebas parasitize in the human large intestine and can dissolve the cells on the intestinal wall, causing“Amebic dysentery”, endangering human health.
The protozoa such as amoeba can be used as an indicator animal to determine the degree of water pollution.
The feeding behavior of amoeba reflects the fluidity of cell membrane.
Amoeba culture
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Amoeba
Danielle(Danielli) andMage soupMaggleton.[3]If the amoeba is always cultivated in a nutrient sufficient culture medium, the amoeba can divide and grow repeatedly, and can survive indefinitely.However, if the amoeba is cultured in a culture medium with nutrients that can only sustain life (called maintenance diet), its division is not only limited, but eventually it dies.If the amoebas are raised in the "maintenance diet" for a few weeks, and then transferred to the nutrient rich medium, these amoebas regain the ability to grow and divide, but they do not divide indefinitely, nor can they survive forever. They will live in bundles after only 210 days.
Later, in order to verify whether the transformation of amoeba from immortal state to finite life state was caused by the change of nucleus or cytoplasm of amoeba, another nuclear transfer experiment was conducted.The experiment is to inject the immortal type nucleus into the finite type cytoplasm, or inject the finite type nucleus into the immortal type cytoplasm, and the result of the experiment is that the transmucleate amoebas are all amoebas with limited lifespan.The experiment proved that the deficiency of nutrients could lead to the imbalance of cell synthesis and the defect of nuclear replication, thus resulting in the defect of its metabolic function.This also shows that metabolic defects are the direct cause of life aging.
collection
Amoeba
(1) Collect from rotten plants in water.In summer and autumn, there are many decaying plants in shallow pools and ditches.They either float or sink in the water.The surface of these decaying plants is a good place for amoebas to live and breed, and there are often many larger amoebas.Collect this rotten plant and put it into a jar, inject proper pool water, take it back to the laboratory to scrape the viscous substances from the surface of the rotten plant, make temporary slides, and put them under a microscope for inspection.If you see some translucent, semi flowing, well-defined, oil like particles in your field of vision, this is an amoeba.
(2) Collect in the water containing diatoms.Amoebas like to eat diatoms. The water containing diatoms is often yellow brown, and there are many yellow brown bubbles on the surface of the nearshore water. In addition to diatoms, there are often many amoebas eating diatoms.You can use a wide mouth bottle to take the pool water with foam and take it back to the room for microscopic inspection.
(3) Collect from fresh straw or wild grass.Amoebas can form dormant cysts in harsh environments.Therefore, amoeba cysts are often attached to the lower part of the stems of fresh rice straw and some waterside weeds.
separate
When the environment suddenly changes, amoebas have the habit of firmly adhering to objects.Using this habit, after finding the amoeba under the microscope, shake the slide containing the amoeba slightly.Then makeSlideTilt, slowly flush with water for a few minutes, and then put it back under the microscope for observation, you can see otheraquaticAll of them have been washed away, and only the amoeba sticks to the slide without moving, thus achieving the goal of separating amoebas.
Preparation of culture medium
AmoebalCulture mediumThere are straw culture liquid, wheat grain culture liquid and rice culture liquid.The preparation principle and method of the first two kinds of culture medium, andparameciumThe culture solution of is the same, that is, take dry straw and cut it into small pieces, soak it directly in water or soak it after boiling, and use the rice straw extract as the culture solution.Then put the soaked straw and water intoGlass containerInside, water accounts for more than 2/3 and is placed in a place with sufficient light.Preparation method of rice culture solution: 400ml water is added with 3~4 grains of rice. This culture solution can often produce a large amount ofColorless flagellate, for amoeba.
culture
After the above separation, only amoebaSlidePutCulture mediumThe mouth of the container containing the culture liquid should be tightly wrapped with gauze and placed in a warm and bright place. After about half a month of culture, a large number of amoebas will be bred.
observation
Amoeba
Use tweezers to removeStraw culture mediumTake out a piece of grass, or take out a grain of wheat or rice from the wheat culture solution or rice culture solution, and gently smear it on the glass slide for a few times, then drop a small amount of culture solution, and put it under the microscope to dim the light of the field of vision, and you will find the amoeba.
After finding the amoeba, changeHigh power objectiveObserve carefully the movement mode and feeding mode of the amoeba, and identify its body structureEctoplasmandEndoplasm, as well as food bubbles and telescopic bubbles in the endoplasm.If usingMethyl greenStaining, you can see the green stained nuclei.[4]
Reasons for not aging
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Why can amoebas divide and grow indefinitely?The main reason is that it has never experienced cell differentiation in its life, and various metabolic bacterial systems that carry out metabolism and maintain life activities all exist in a single cell, making its cell itself an independent life entity, and its offspring will always maintain the characteristics of this life, that is, the complete metabolic function is maintained by a single cell.
