Life Cycle of Amoeba
It's one of the most abundant life forms on the planet, but chances are, unless you've peered through the eyepiece of a microscope, you've never seen one. Consisting of but a single cells and measuring an average of just 10 microns across, amoebae (plural of amoeba) are generally invisible to the naked eye, but their apparent simplicity contrasts with the intricacy of their life cycle.
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Basics
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Despite their primitive structure, amoebae are among the most well-adapted and widespread creatures on Earth. From lakes, to oceans, to soil, and even nestled inside marine and terrestrial organisms (including human beings), the unicellular organisms are found almost everywhere. It's difficult if not impossible for any animal to avoid their parasitic invasiveness that is often benign but sometimes pathogenic. A genus of protozoan, amoebae can attribute their numerical success to their method of reproduction, which is asexual.
Mitosis
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When conditions are favorable, a single adult amoeba will employ a biological process known as cytokinesis to literally "split" itself in two, thus producing two amoebae known as "daughters." First, the single nucleus of the parent amoeba undergoes mitosis, in which it splits to provide a nucleus for each daughter. If conditions do not favor mitosis, the single amoeba will not split, and instead will secrete a protective coating, armoring itself in a state known as a microbial cyst, until conditions improve and it can to return to its metabolically active trophozoite state, in which it can split.
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Feeding
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The first order of business for the newly birthed amoeba, as with other organisms, is finding a usable food source. Lacking a mouth, the amoeba uses an action known as phagocytosis to catch and ingest its food. Encountering a potential meal (which usually consists of microscopic particles, e.g. algae, bacteria and other amoebae), the amoeba employs a temporary set of tentacle-like structures known as pseudopodia to capture and engulf it. It secretes digestive enzymes into the pocket thus formed, called a food vacuole, in which the food is digested.
Excretion and Respiration
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From its meal, the amoeba will absorb any useful nutrients into its body. Anything potentially harmful or superfluous stays within the food vacuole until it's eventually pushed to the surface through the cell membrane. This process is known as egestion. A similar tactic is used for the expulsion of gases, which diffuse via the cell membrane.
Adulthood
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Though there are many different amoebae and varying life cycles, most are exact copies of their parent. When they reach maturity, they divide via mitosis and begin the process of splitting, eating and maturing all over again.
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