THE STRUCTURE AND LIFE PROCESSES PARAMECIUM
Objectives
This blog post provides readers with the following objectives. The reader will be able to:
o Describe the structure of Paramecium.
o Explain the life processes of Paramecium.
Paramecium Caudatum
Kingdom: Protoctista
Phylum: Ciliophora
Habitat: muddy polluted, fresh water ponds and ditches
Structure of Paramecium
It has a fixed slipper shaped and is about 0.24mm in length. It has transparent body (with rounded anterior end and pointed posterior end), enclosed by elastic membrane called pellicle.
Beneath the pellicle are oval bodies called trichocytes used for defense.
The whole body is covered by tiny, hair-like protoplasmic threads called cilia. The cilia are interconnected at their basal bodies by fine fibers called neuronemes.
The cytoplasm is divided into outer layer (plasmagel) and inner layer (plasmasol).
It has two nuclei; the large and bean-shaped nucleus called meganucleus and the smaller spherical nucleus called micronucleus which lies just close to the mega-nucleus.
There are two star shaped contractile vacuoles lying at the anterior and posterior end.
The ventral side of the body is hollowed out to form oral groove which leads into the gullets in the endoplasm. The gullet, in turn leads into the cytostome (mouth pore).
Life Processes of Paramecium
Excretion in Paramecium
Waste products such as carbon dioxide, urea and ammonia are diffuse through the cell membrane.
Excess water is carried out by the two contractile vacuoles that work alternatively.
Locomotion in Paramecium
Osmoregulation in Paramecium
Response to Stimuli
Nutrition in Paramecium
Paramecia feed on bacteria, algae, yeasts, diatoms and decaying organic matter. The cilia beat frequently to create water current, which drives food along the oral groove into the cytostome where they are ingested in a food vacuole.
Food vacuole circulate through the cytoplasm, and enzymes are secreted into the food vacuole to breakdown the content.
The digested nutrients are then absorbed into the cytoplasm. The undigested food is released through a special opening called anal pore.
Respiration in Paramecium
Reproduction in Paramecium
Reproduction involves Asexual and Sexual reproduction.
Asexual reproduction
Paramecium reproduces asexually, by binary fission. The macronucleus splits and the micronucleus divide and move to opposite ends of the organism. The cell then divides transversally to produce two new paramecia.
Sexual reproduction
Sexual reproduction under unfavorable conditions paramecium undergoes sexual process known as conjugation. The two organisms involved in conjugation are called conjugants. During conjugation, two paramecia come together and unite at their oral grooves. The meganuclei disappears, and the micronucleus divides into four. Three of the four nuclei of each conjugant disintegrate and the remaining one divides into two active and passive nuclei. Exchange of active nuclei occurs between the two conjugants. Fusion occurs after interchange of nuclei to form a zygotic nucleus. The paramecia separate from each other and the zygotic nucleus in each divides thrice by mitosis to form eight nuclei. Each conjugant undergoes two binary fissions to produce four paramecia. Each daughter paramecium has two nuclei which develop into the meganucleus and micronucleus.
%20in%20paramecium.webp "Sexual reproduction in paramecium")
Adaptation
1. It possesses numerous cilia for locomotion.
2. It possesses contractile vacuole for osmoregulation.
3. It possesses a pellicle, which gives it a definite shape
4. It possesses trichocytes, which are used for defense and attack.
5. The presence of oral groove enables it to feed.
Conclusion
Paramecium is a highly organized and complex single-celled organism, demonstrating various life processes that allow it to survive and thrive in its aquatic environment. Its structure, from the pellicle and cilia to the macronucleus and contractile vacuoles, supports its locomotion, feeding, digestion, excretion, respiration, reproduction, and response to stimuli. Studying Paramecium provides valuable insights into the fundamental mechanisms of cellular life and the adaptability of single-celled organisms.
For further reading, you can explore more detailed information on the structure and life processes of Paramecium on Britannica and National Center for Biotechnology Information (NCBI).
References
- Englund PT, Sher A (eds): The Biology of
Parasitism. A Molecular and Immunological Approach. Alan R. Liss, New
York, 1988 .
- Kotler DP, Orenstein JM. Prevalence of Intestinal Microsporidiosis in HIV-infected individuals referred for gastrointestinal evaluation. J Gastroenterol. 1994;89:1998. [PubMed]
- Goldsmith R, Heyneman D (eds): Tropical Medicine
and Parasitology. Appleton and Lange, East Norwalk, CT, 1989 .
- Lee JJ, Hutner SH, Bovee EC (eds): An Illustrated Guide to the Protozoa. Society of Protozoologists, Lawrence, KS, 1985 .
