Exceptions to the cell theory, Biology

Exceptions to the Cell Theory

Viruses, however, are not the only exception to the Cell Theory as formulated earlier. This has led scientists to take a much broader view of the problem. some organisms like a bacterium, blue-green alga, mycoplasma, amoeba, Chlamydomonas and Mucor are composed basically of a single cell.-In such cases we face another problem. You have so far learnt that the cell is the basic structural unit of an organism, something like bricks in a building.

But in the examples cited above just a single cell constitutes the whole animal, which amazingly performs all the body functions like respiration, digestion, excretion, etc. The problem is further complicated by the occurrence of many multinucleate protozoans, multinucleate animal tissues etc.For example a species of amoeba, Chaos as well as also many other protists like the ciliate Opalina have many nuclei in their body. The common. pond plant Nitella has giant cells with many nuclei in the cytoplasm. There are also tissues and cells in our body which have many nuclei.

Such cells are called syncytial. For example, the striated muscle fibres of our body are syncytial in nature. The problems listed above arose due to the fact that Cell Theory was proposed on the basis of observations on multicellular organism. This created a wrong notion that single celled organisms were totally comparable to a cell of multicellular organisms. It is however, now established beyond any doubt that as it stands today, the present unified Cell Theory given below, is universally applicable with equal force from bacteria to protozoa to humans except for viruses.

Posted Date: 1/12/2013 2:58:29 AM | Location : United States







Related Discussions:- Exceptions to the cell theory, Assignment Help, Ask Question on Exceptions to the cell theory, Get Answer, Expert's Help, Exceptions to the cell theory Discussions

Write discussion on Exceptions to the cell theory
Your posts are moderated
Related Questions
Failure of implant The implant is considered a failed implant if it presents with even any one of the following features: i) Pain on function (Rule out pain due to soft tis

Each of the properties that follow is characteristic of the carbon atom. In each case, indicate how the property contributes to the role of the carbon atom as the most important at

Q. What is the intermediate host of Schistosoma mansoni? Where does that host live? The intermediate host of a schistosome is a gastropod mollusc, Biomphalaria genus and a snai

two larva forms of sponge

Porcine rotavirus Piglet diarrhoea and mortality are gaining importance and the viral agent which is highly incriminated in such episodes is porcine rotavirus. The clinical featur

Phylum-Bacteria (Eubacteria) Eubacteria,th e true bacteria, are extremely small and they exist in vast numbers virtually everywhere on earth. They range from the upper atmosphe

characters of phylum protozoa

The pancreas produces insulin, a hormone that is specifically produced in the beta cells of the pancreas and it is responsible for the regulation of blood glucose. After carefull c

Explain Protoderm in primary growth in shoot? The protoderm is one of the so-called "primary tissues" because it is formed first during germination and subsequent bud growth an

Lumpy skin disease The disease, reported from Sudan in 1970 and Egypt in 1988, is caused by a member of the Capripox virus. It affects cattle and is restricted to African coun