Unified cell theory, Biology

Assignment Help:

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)


Related Discussions:- Unified cell theory

What is gene, What is gene? Gene is a sequence of DNA nucleotides that ...

What is gene? Gene is a sequence of DNA nucleotides that codifies the production of a protein.

Viruses, what are viruses?its history?its life cycle and the diseases cause...

what are viruses?its history?its life cycle and the diseases caused by it?

Animals of the littoral zone, Animals of the littoral zone Animals of...

Animals of the littoral zone Animals of this zone may be herbivores, carnivores or detritus feeders and are as diverse as plants. Many of them such as rotifers, protozoans, i

Chemoreceptors, Chemoreceptors These are receptors included in percept...

Chemoreceptors These are receptors included in perception of chemical stimuli. You will see that there are three kinds of Chemoreceptors among metazoans:  i) Those concerne

What are neurons, Question 1 Give the definition and describe the mechanis...

Question 1 Give the definition and describe the mechanism of Active transport. Passive transport with suitable examples Question 2 What are neurons? List out the

Which statement is false, Which is FALSE? Diastereomers: Select one: ...

Which is FALSE? Diastereomers: Select one: a. Have the same molecular weight b. Have the same connectivity c. Are mirror images d. All of the above e. None of the

Define the advatages of potassium, Define the advatages of Potassium Th...

Define the advatages of Potassium The gross impact of these effects on crop production is manifested  in several ways. Perhaps the first visible indication of a potassium defic

Social health insurance systems, Normal 0 false false false...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Explain the functional properties of proteins, Functional properties of pro...

Functional properties of proteins These are those physico-chemical properties that enable the proteins to contribute to the desirable characteristics of the food Potential f

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd