What is a Paramecium?
A paramecium is a unicellular (one cell) eukaryotic organism generally found in stagnant water. While very small, sometimes large paramecium can be seen as tiny specks darting around in a water sample. Paramecium can be about 0.5 mm long.
Discover for Yourself
Use a metric ruler to draw a line 0.5 mm long. This gives you an idea how small paramecium are.
What are Eukaryotics?
Eukaryotes are organisms with one or multiple cells, which contains a membrane-bound nucleus or nuclei. Eukaryotic cells contain other organelles (organs within a cell). The paramecium represented in the diagram does not include all the organelles contained in an eukaryotic cell. It is a simple representation of a paramecium, which like all eukaryotes has other organelles, including a mitochondria and endoplasmic recticulum. Multicullar eukaryotes include animals, plants, and fungi. Unicellular eukaryotes include paramecium.
The contents of the paramecium is bound by a cell membrane, which is covered by a pellicle, which is a stiff but elastic membrane. The pellicle gives the paramecium a definite shape but it is flexible enough to allow small shape changes.
Following are cell parts and functions that keep the single-cell paramecium alive. Numbers in parenthesis relate to the diagram of the paramecium.
Oxygen enters and waste carbon dioxide exits through the cell membrane. Energy is produced in mitochonria (not shown) via the respiration reaction represented by this equation:
Food + Oxygen yields carbon dioxide + water + Energy
The endoplasmic reticulum (not shown) stores food.
Covering the pellicle (outer covering of the cell) are many tiny hair-like structures, called cilia (1). The beating of the cilia is much like the movement of boat oars, they push the paramecium so that its anterior (front) end moves forward. Paramecium have no eyes, so if they hit something solid, they back up, make changes in direction and proceed forward again as shown in the diagram.
Ingestion is taking food into the body. On the side of a paramecium about mid-way is the oral groove (2). As the paramecium moves forward, water with food, including bacteria and algae are swept into the oral groove. At the posterior end of the oral groove is the gullet where food collects. As more food collects the end of the gullet balloons out and eventually breaks off as a food vacuole (3).
Digestion is the breaking down of food into small particles that can be used by the cell. The food vacuole (3) breaks away from the gullet at the posterior end and moves through the cytoplasm (5), which is the gel-like material within the cell. As the food vacuole moves, enzyme from the cytoplasm enter the vacuole and digest the collection of food, including bacteria, algae and/or yeast. After being digested, the nutrients moves through the membrane of the vacuole into the cytoplasm. As this process continues, the vacuole decreases in size. When the shrunken vacuole completes it journey, the vacuole and its remaining undigested food is eliminated through the anal pore (4).
Along with the anal pore (4), which eliminates solid wastes, paramecium have contractile vacuoles (6), which eliminate water. Contractile vacuoles are located near the surface and at either end of the cell. Waste gas, carbon dioxide, passes through the cell membrane into the water outside the cell.
Paramecium reproduce asexual by binary fission in which a fully grown organism divides into two separate daughter cells; The micronucleus (8) contains genetic material necessary for reproduction.
Real World Applications: Careers
Studying microorganisms is part of many biology, medical, and health careers. Continued investigation of celestial bodies expands the need to understand the effect of microgravity on microorganisms. Where ever humans go, they carry microorganisms with them. NASA is now studying microorganisms taken from the International Space Station(ISS). How does being in space change microbes within the ISS. There is no limit to careers that will continue to spin off due to NASA’s space program, such as Astromicrobiology, Microbe Engineer, Genetic Engineering, etc…………………………
For more information about microbes and their environment, see Janice VanCleave’s Ecology for Every Kid.