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
Q. How Time affecting taste quality? Time- Time is another factor which affects sensation. Salt on tongue is sensed in a fraction of a second; whereas, bitter things may requir


SED A TIV E HYPNOTICS - They depress the activity of CNS. Reduce excitement, give feeling of calm. Higher doses induces sleep. Sleep inducing drugs are also called

How are the main classes of arthropods classified according to the presence of larval stage in their embryonic development? In crustaceans there are species with direct and oth

Q What is the alternative means for transport of substances in animals without a circulatory system? Why is blood important for larger animals? In animals that don't present th

Individuals with tyrosinenmia have food patterns very similar to the one for PKU discussed above. PKU is more common than tyrosinemia. Foods that are high in tyrosine and phenylala

Cohesion-adhesion theory describes the properties of water which help move it through the plant. Cohesion is the property of water molecules to stick together (held by hydrogen bo


Testing whether roots absorb water and suspended solids Three same plants are inserted into test tubes having 1, water; 2, red ink; 3, a suspension of Congo red. After a some d

What is the most accepted hypothesis about the origin of life on earth? How does it compare to the other main hypotheses? The heterotrophic hypothesis is the strongest and most