The intake of nutrition takes place in the in the following 5 steps:. The processes involved in holozoic nutrition in amoeba are:.
The process of taking in the food into the body either by swallowing or absorbing it is called the procedure of Ingestion. Amoeba oozes out the pseudopodia to encircle the food and engulfs it forming a food vacuole. This process is known as phagocytosis. The process of breaking the insoluble and enormous food molecules into soluble and minute molecules is called the process of Digestion. In amoeba, the food vacuoles are put deeper into the cell, and with the assistance of the digestive enzymes, the massive insoluble particles are churned down to the simpler molecules.
The biochemical substances present in the food are called nutrients. On the other hand, digestion is a step of nutrition that involves the breakdown of complex food molecules into simple food molecules. Organisms that are unable to prepare their food and are totally dependent on others for food are called heterotrophs, and their mode of nutrition is called heterotrophic nutrition.
Amoeba exhibits a holozoic mode of heterotrophic nutrition. When organisms engulf the solid, complex food through their mouth or cell membrane and break it down inside the gut or cell, the mode is called holozoic nutrition or ingestive nutrition.
In Amoeba , the solid food particles are engulfed by the temporary finger-like projections called pseudopodia and further digested in the cell. Paramecium , fishes, amphibians, reptiles, birds, mammals, and humans also exhibit the holozoic mode of nutrition. Fig: Amoeba. Feeding is the process of intake of food.
Nutrition in animals depends on their feeding habits. Simple organisms like Amoeba, Paramecium do not have any specific part or organ for the intake of food. Structures like pseudopodia, cilia help to sweep the food inside the cell.
Advanced organisms like mammals, reptiles have a specific opening called the mouth for the intake of food. Amoeba performs feeding with the help of the formation of pseudopodia.
This process is called phagocytosis. In this process, once an Amoeba captures the food with the help of pseudopodia and encloses it in a vesicle called a phagosome, where the food is digested with the help of enzymes.
The steps involved in nutrition in Amoeba are similar to those of complex organisms like humans. These steps are as follows: 1. Ingestion 2. Digestion 3. Absorption 4. Assimilation 5. Ingestion means the intake of food. Amoeba does not have a specific opening mouth for the ingestion of food. The food particle is engulfed by the formation of pseudopodia a temporary protrusion of the cell surface.
The food is engulfed with a little amount of surrounding water to form a food vacuole. This food vacuole is also called the temporary stomach of Amoeba.
Depending upon the gross size of food particles, feeding in animals may be classified into two categories: macrophagy ingesting large food particles as in chordates , microphagy ingesting small food particles as in microscopic animals; Amoeba , Paramecium.
Digestion is the process of the breakdown of complex organic food molecules carbohydrates, proteins, fats into simple food molecules. It is catalysed by digestive enzymes. When this happens, the contractile vacuoles can store extra water and help in throwing them together with the wastes out of the cell. Without the contractile vacuoles, the amoeba may burst. Undoubtedly, it is a very important organelle with an essential function to the amoeba, as well as many freshwater microorganisms.
The contractile vacuole is the key regulator of osmotic pressure in the amoeba also in many single-celled protists. Contractile vacuole serves as a reservoir to store excess water inside the cells. Once the water is close to its limit, the contractile vacuole moves and fuses with plasma membrane to expel water. The third secret of Amoeba proteus is its cell membrane is not that smooth like it shows under the optical microscope. In fact, the outside face of the membrane has many microvilli attached to it can only be seen under an electron microscope.
These microvilli can help Amoeba proteus attach and release from the surface of the substrate. The size ranges based on the amount of food it engulfs. It can almost be seen with the naked eye still very difficult due to its colorless and transparent body. A Megaphragma mymaripenne. B Paramecium caudatum. C Amoeba proteus. Megaphragma mymaripenne, a parasitic wasp, is the smallest known flying insect.
However, Amoeba proteus can sense light and tends to move away from it. Bright light can even make all movements cease suddenly. The scientists found that Amoeba proteus can respond to light stimulus because of reactions in its plasmagel, the gel-like cytoplasm at the tips of pseudopods. The light makes its plasmagel thicker and stiffer, and as a consequence, more difficult to move. Other than light, Amoeba proteus can also sense several stimuli, like chemicals, toughing, temperature, and even electric field!
It also does not stay in the complete dark due to the lack of food. Amoeba prefers in a dim light environment like under the shadow of water plants or rocks. If possible, it will like to adhere to the surface of the substratum. Because the Amoeba proteus is a single-celled organism, oxygen and carbon dioxide can freely diffuse in and out of its cell membrane.
Also, other substances water-soluble molecules like salt are able to transport through the membrane by osmosis. Just before it reproduces, Amoeba proteus retracts most of its pseudopods and rounds up into a ball. After replicating its genetic material DNA in the nucleus, the original nucleus of the Amoeba divides to form two daughter nuclei by the process of Karyokinesis. In this process, the long DNA molecules condense into chromosomes rod-liked shape to facilitate the separation.
After the nucleus has divided into two, the process of Cytokinesis takes place in which the cytoplasm in the mother cell pinches in and divides into two daughter cells. This leads to the formation of the two daughter Amoebae cell, having a nucleus and its own cell cytoplasm and organelles. Usually, the entire process may last anywhere from 30 minutes to an hour. Most of the time, amoebas reproduce by the binary fission. When the environment is turning harsh, amoebas adapt to the multiple fission to increase the chance to survive.
There is another rare way for Amoeba to reproduce, called Encystment or Multiple Fission. When amoeba senses the environment become unfavorable eg. This cyst is able to survive in much harsher conditions. At the same time, mitosis occurs many times inside the cyst, producing more than two daughter cells.
When the cyst wall ruptures when the condition turns favorable , these daughter cells are then released to become several new amoebas. When the environment of habitation becomes extremely unfavorable, Amoebas will reproduce through spores. This sexual reproduction can create genetic diversity and increase its chance to survive in a harsh conditions.
Amoeba proteus likes to stay at the bottom of clean freshwaters. It is found feeding on decaying substances on the bottom of freshwater streams and stagnant ponds. You can use a transfer dropper to collect the bottom sediments to look for Amoeba proteus.
Amoeba proteus can also be ordered from science supply companies and is the classic specimen used in the classroom to demonstrate the pseudopods in action. Here are some pictures of habitations where I recently spot Amoeba proteus. A-C Amoebas like to hide in the bottom sediments like leaves of clear water ponds. D-E I used the forceps to collect some decaying leaves and water with sediments into my sample vial.
I will bring it home to look for amoebas and other pond lives under my microscope. Amoebas can be directly observed under an optical microscope without additional stains. It takes patience to locate Amoebas under the microscope because they are transparent color-less , slow-moving, and like to cover themselves under debris or bottom sediments.
Use a transfer pipette to get a drop of water with some bottom sediments onto a microscopic slide. Gently cover the sample with a coverslip and mount it on the microscope stage for viewing. Wait minutes to allow the microorganisms adapting to the new environment amoebas like to adhere to the surface of the glass. Gradually increase the illumination Amoebas are sensitive to bright light and scan the field by low magnification 5x or 10x. Looking for the tiny crystal-liked particles inside the cells of Amoebas may help you locate them.
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