i just love Amoebae. I love watching them ooze about under a microscope. I love the idea of something so small yet so... alive. They are single-cellular protozoans, little animals that stalk their prey, pounce and feed, digest and excrete and move, move, move. Their world is a drop of water and the whole pond is their universe. They do not have eyes but they can sense light. They have no brains but somehow they can figure out where food is, go there and get it. They can also recognise certain kinds of dangers and move away. How do they move? With 'pseudopods" or false feet.
Let's start at the beginning: there is a cell, defined by its membrane. Within the cell is jelly-like cytoplasm (translation: cell stuff). The cell-jelly comes in two forms: gel which is fluid and sol which is more... solid. When the cell 'decides' to move, the gel part flows in that direction, pushing the membrane out into a 'pseudo-foot'. If a food item such as a ciliate (protozoan that moves by little oars called cilia) is contacted, the pseudopods surround it. Then a hole appears in the membrane and the ciliate is engulfed into the Amoeba. The cell digests the prey, converts it to fats for burning into energy in the mitochondria, and the wastes are chucked back out via another hole in the membrane.
So simple yet so effective. Amoebae ooze through their world, munching up algae and smaller protozoans so they can grow, grow, grow, until its time to split. No sex for these critters - just basic cell division, the same mitosis that our own cells indulge in to grow our bodies. First the chromosomes line up, double and then separate into two groups. Then the nucleus pulls apart into two nucleii, each with a full set of chromosomes with all the chemical knowledge to run a new amoeba. They migrate to opposite sides of the 'mother' cell which is pulling apart to make two 'daughter' cells.
Mother cell to daughter cells, mothers to daughters, over and over, not just for days, weeks, months or years. Not just for 6000 years or 100,000. Protozoa go back to the very beginning, the mythical magical Primeval Soup where life as we know it began, some 3-4 billion years ago. Amoebae are as young as an hour ago when they last divided and almost as old as Life itself. Only Bacteria and other anucleates are older - the Prokaryotes. Amoebae are as close as no matter to the original Eukaryotes from which we are all descended. And even after we split off and became multicellular and divided into the wondrous diversity of species and forms, the Amoebae kept dividing and surviving, in spite of us and sometimes because of us.
Some Amoebae have become parasites. Entamoeba coli lives in our intestines with little harm to us but Entamoeba hystolitica causes amoebic dysentery. How many humans have died from that over the last millenia? Parasitic amoebae have been found in contact lenses (, threatening the wearer's eyes. There is a rarewww.eurekalert.org/pub_releases/2008-10/sfgm-cla102008.php), water-borne disease in America caused by a brain attacking amoeba (http://www.msnbc.msn.com/id/21034344/. Amoebae may be implicated in Legionnaire's Disease as an intermediate host (http://www.faqs.org/abstracts/Health/Association-of-shower-use-with-Legionnaires-disease-possible-role-of-amoebae.html.
Most amoebae are free-living. Pick up a microscope and have a look in your local pond water. It will take a lot of patience but you may just be lucky enough to see one of these strange creatures in action.