Unified cell theory, Biology

Unified Cell Theory

The present unified cell theory states that

  1. All living things are composed of either a single Cell or of the cells and cell products. The cell is a mass of protoplasm limited by a cell membrane, and possessing a nucleus;
  2. New cells are formed only by division of pre-existing cells;
  3. There are fundamental similarities in the chemical constituents and metabolic activities of all cells;
  4. The activity of an organism as a whole can be understood as the collective activities and interaction of its interdependent cellular units.

In view of this present cell theory the living organisms may be broadly divided into:

  • Acellular forms with body not composed of cells, for example viruses. 
  • Cellular forms with body composed of cells.

The cellular forms may further be classified into:

a) Unicellular organisms with only one cell in their body, for example bacteria. blue-green algae, protozoans, etc. and
b) Multicellular organisms having many cells in their body. In such forms the cells organise themselves into tissues, tissues into organs and organs into organ systems. Examples of these are animals ranging from sponges to man and plants ranging from most algae to all flowering plants.

1295_Unified Cell Theory.png

Figure: Some unicellular organisms: (a) Bacterium (Escherichia coli), (b) Blue green alga,(c) Mycoplasma, (d) Amoeba (a protozoan), (e) Chhydomonus (an alga), and (f) Mucor (a fungus)

Posted Date: 1/12/2013 3:04:32 AM | Location : United States







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

Write discussion on Unified cell theory
Your posts are moderated
Related Questions
Caruncle - Seed Appendages This is a white, collar-like structure borne on the micropylar end of the seed in many members of the Euphorbiaceae, such as castor, Ricinus communi

Q. Explain Food borne toxic infections? Ans. The food borne toxic infections, you may recall reading earlier, are caused by the ingestion of a large numbers of ent

Explain about the Physiological Accommodation Physiological Accommodation contractile power of the ciliary muscle required to change the focussing power of the eye by ID. Meas

Can all the four chambers of the human heart experience systole simultaneously? Describe justifying your answer. What do you call the circulatory fluid in the body of cockroach

You have discovered a novel alternatively spliced gene (gene X) and you wish to study its regulation in an in vitro splicing assay.  The alternatively spliced product retains intro

Define Chromatography - Basic Separation Technique? Chromatography is the most effective technique for the separation, purification and identification of one or more biological

Q. What is the kind of digestive system present in beings of the phylum Arthropoda? Are these animals deuterostomes or protostomes? The digestive tube of arthropods is complete

A glycogen molecule having entirely of glucose units, many of that are linked in long chains through α1-4 bonds.  Furthermore,  every  10  units  or  so,  the  chain  is branched

Q. What is the general equation of the aerobic respiration (also representing phosphate and ADP)? The general  chemical equation of the aerobic respiration is: C 6 H 12 O 6

What is the connection between tissue fluid, plasma and lymph? Tissue fluid is plasma (minus its proteins) which has leaked out of the capillaries. Lymph is tissue fluid which