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

Diffusion, applications of diffusion

applications of diffusion

What is the second polar body, Q. What is the second polar body? After ...

Q. What is the second polar body? After termination of the second meiotic division of the oocyte II two cells are generated: the second polar body and the egg cell proper. The

What do you mean by polyphagia, Q. What do you mean by Polyphagia? Incr...

Q. What do you mean by Polyphagia? Increased Hunger (Polyphagia): As patient is losing more sugar in the urine, he feels hungry very soon and tends to take more food. It is cal

Compute the osmolarity of a solution, Calculate the osmolarity of a solutio...

Calculate the osmolarity of a solution of 5% dextrose in water (dextrose = glucose, molec. Wt. = 180).

Oogenesis in mammals, Oogenesis in Mammals In mammals also the oogoni...

Oogenesis in Mammals In mammals also the oogonial cells are derived from primordial germ cells. The multiplication phase, that is all of the oogonial divisions and transforma

Heart - investigation of hypertension, The complications that occur in the ...

The complications that occur in the heart due to hypertension are left ventricular hypertrophy, diastolic dysfunction and cardiac failure. There is also associated coronary artery

Mismatch and recombinational repair, Q. Mismatch and Recombinational repair...

Q. Mismatch and Recombinational repair? Mismatch repair: 1. Mismatches can take place when DNA polymerase inserts wrong nucleotide during replication 2. Mismatch repair is

Demonstrate the structure of mitochondria, Demonstrate the structure of mit...

Demonstrate the structure of mitochondria The structure of mitochondria has been examined in great detail with the aid of the electron microscope, and it is now possible to des

Calculate the level of magnesium in urine, Calculate the Level of Magnesium...

Calculate the Level of Magnesium in urine? Urinary Mg excretion decreases with Mg deficiency. Therefore, Mg excretion before and after administration of an intravenous Mg load

Calorie requirements for ulcerative colitis, Q. Calorie requirements for ul...

Q. Calorie requirements for ulcerative colitis? Energy: The calorie requirements must be increased to: 1) Restore weight status and maintain ideal weight. 2) Compensate 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