The widest part of the body is below the middle. The body of a paramecium is asymmetrical. It has a well-defined ventral or oral surface and has a convex aboral or dorsal body surface. Its whole body is covered with a flexible, thin and firm membrane called pellicles. These pellicles are elastic in nature which supports the cell membrane. It's made up of a gelatinous substance. Cilia refers to the multiple, small hair-like projections that cover the whole body.
It is arranged in longitudinal rows with a uniform length throughout the body of the animal. This condition is called holotrichous. There are also a few longer cilia present at the posterior end of the body forming a caudal tuft of cilia, thus named caudatum. The structure of cilia is the same as flagella, a sheath made of protoplast or plasma membrane with longitudinal nine fibrils in the form of a ring. The outer fibrils are much thicker than the inner ones with each cilium arising from a basal granule.
Cilia have a diameter of 0. It contains the following parts:. The nucleus further consists of a macronucleus and a micronucleus. Paramecium consists of two types of vacuoles: contractile vacuole and food vacuole. Habit and Habitat. Paramecium has a worldwide distribution and is a free-living organism. It usually lives in the stagnant water of pools, lakes, ditches, ponds, freshwater and slow flowing water that is rich in decaying organic matter.
Movement and Feeding. Its outer body is covered by the tiny hair-like structures called cilia. Just as the organism moves forward, rotating around its own axis, this further helps it to push the food into the gullet. Life without a nucleus Bacteria and Archaea seem to have a lot in common at first. More complex life The third domain, Eukarya, differs greatly from the other two.
The paramecium is a unicellular eukaryote. Read more prokaryote eukaryote archaea cell nucleus unicellular multicellular fungus algae. Both scale bars are micrometers. Although P. Photo credit: P. Although paramecium is small and has only one cell, it can do everything that a living creature can do: Paramecium can swim, digest food, and reproduce.
Paramecium constantly moves by beating rows of microscopic hairs, called cilia singular cilium , that work like miniature oars. This is why paramecium is commonly studied as a white rat of ciliates. Certain paramecia are also easily cultured in labs and serve as useful model organisms.
Paramecium collects foods via its mouth, called oral groove. The food materials enter the cell body and then are digested in food vacuoles. Paramecia eat other microorganisms such as bacteria, yeasts, and algae. Paramecium has a protective skin layer consisted of pellicle and ectoplasm. Trichocysts are special organelles situated in the ectoplasm which can discharge long spikes for protection from their predator. The most unusual characteristic of paramecia is their nuclei.
They have two types of nuclei, micronucleus, and macronucleus. The macronucleus controls non-reproductive cell functions, expressing the genes needed for daily functions, such as movement and feeding. The micronucleus is the germline nucleus, containing the genetic material that passed along from one generation to the next generation.
Paramecium has two star-shaped contractile vacuoles. The contractile vacuoles regulate the quantity of water osmosis inside of a cell. They expel water out of the cell by contracting and they prevent the cell from absorbing too much water.
Paramecia can reproduce either asexually or sexually, depending on their environmental conditions. When nutrients are plentiful, the population of paramecia increases rapidly by asexual reproduction, called binary fission. Most protists have mitochondria , the organelle which generates energy for cells to use. The exceptions are some protists that live in anoxic conditions, or environments lacking in oxygen, according to an online resource published by University of California, Los Angeles.
They use an organelle called the hydrogenosome which is a greatly modified version of mitochondria for some of their energy production. For example, the sexually transmitted parasite Trichomonas vaginalis , which infects the human vagina and causes trichomoniasis , contains hydrogenosomes.
Protists gain nutrition in a number of ways. According to Simpson, protists can be photosynthetic or heterotrophs organisms that seek outside sources of food in the form of organic material. In turn, heterotrophic protists fall into two categories: phagotrophs and osmotrophs. Phagotrophs use their cell body to surround and swallow up food, often other cells, while osmotrophs absorb nutrients from the surrounding environment.
They have their own plastids, but will also happily eat other organisms. Most protists reproduce primarily through asexual mechanisms according to Simpson.
This can include binary fission, where a parent cell splits into two identical cells or multiple fission, where the parent cell gives rise to multiple identical cells.
Simpson added that most protists probably also have some kind of sexual cycle, however, this is only well documented in some groups. The classification history of protists traces our understanding of these diverse organisms. Often complex, the long history of protist classification introduced two terms, still used today, into the scientific lexicon: protozoa and protists.
However, the meaning of these terms has also evolved over time. The observable living world was once neatly divided between plants and animals. But the discovery of various microscopic organisms including what we now know as protists and bacteria brought forth the need to understand what they were, and where they fit taxonomically.
The first instinct of scientists was to relate these organisms to plants and animals by relying on morphological characteristics. The term protozoan plural: protozoa or protozoans , meaning "early animals," was introduced in by naturalist Georg A. Goldfuss, according to a article published in the journal International Microbiology.
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