Cell theory, Biology

Assignment Help:

Cell Theory

The invention  of  the  compound microscope  in  the 17th century stimulated the  interest in living things not  visible  to  the  naked  eyes. Thus, Robert Hooke discovered  'cells'  in 1665 by  examining cork  slices  (,under  a crude microscope. He was  actually describing  the spaces occupied by  the cells  limited by  the cellulose walls. Hooke and his contemporaries also described cells from other plants  and  animals.

 

1299_Cell Theory.png

Figure: A generalized plant (a) and animal (b) cell. No one cell of either plant (a) or animal (b) has all the characteristics shorn in these composite figures. Both these are

 

However, cell theory, one of  the  greatest  and most basic generalizations of  biology, was formulated only  about 200 years later. Two German  investigators, Schleiden a botanist (1838), and Schwann, a zoologist  (1839) are credited with  presenting  independently the first concise, yet  comprehensive, statements about the cell. They  pointed out  that, "All plants and. animals are made up of  small fundamental units called cells and that some organisms are unicellular and others, multicellular." Subsequent researched  to the expansion of  this concept by  including further information on  cells. We  know that cells are surrounded by  cell membrane and contain cytoplasm and  nucleus and, most importantly, cells divide into  roughly  equal daughter cells by  a process called  cell division. Thus it became known  that new  cells come into existence only by the division of  previously  existing cells.  In  other words,  cells do not  arise by spontaneous generation  from  nonliving matter. It  follows that all cells living  today  can trace their ancestry back  to those which  existed  in  ancient times.

 


Related Discussions:- Cell theory

What is barr body genes, Q. What is Barr body Genes? Located inside nuc...

Q. What is Barr body Genes? Located inside nuclear envelope, it's a densely staining object which is an inactivated X chromosome in female mammalian cells. Most Barr body genes

Determine the atp-sensitive potassium channel, ATP-sensitive potassium chan...

ATP-sensitive potassium channel A. The channel is a spanning protein with a receptor site for ATP located on an intracellular region of the protein. B. When blood plasma lev

What is the type of circulatory system present in arthropods, What is the t...

What is the type of circulatory system present in arthropods? Do these animals have heart and respiratory pigments? In arthropods the respiratory system is open (lacunar). Blo

Rare species - wildlife, Rare Species - Wildlife These are those speci...

Rare Species - Wildlife These are those species whose numbers are few or they live in such small areas or in such unusual environments (endemics), that they could quickly disa

Management of hypertension, Q. Management of hypertension? the manageme...

Q. Management of hypertension? the management of hypertension, angina pectoris and myocardial infarction. It must be clear to you that some aspects of dietary management may di

Determinants of health status, Determinants of Health Status The linkage...

Determinants of Health Status The linkage between economic development and health was discussed in the previous unit. The present unit deals with an identification of the factor

Distribution coefficient -terminology used in chromatography, Distribution ...

Distribution Coefficient - Terminologies used in Chromatography? During the purification or separation of the biomolecules it should be kept in mind that two important factors

Implantation, Implantation : It is the process in which the blastocyst (de...

Implantation : It is the process in which the blastocyst (developing zygote) is attached to the glandular uterine wall and then embedded in the wall of uterus. 1) In human bein

Woodland stage - hydrarch, Woodland Stage - Hydrarch When the lowland ...

Woodland Stage - Hydrarch When the lowland has been built up to an extent where the soil is saturated perhaps only in spring and early summer, certain species of shrubs and tr

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