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

Define direct measurement of individual''s work capacity, Define Direct mea...

Define Direct measurement of individual's Work Capacity? Direct measurement of VO 2 max is determined by having the subject perform exercise at increased loads, for 12 to 15 m

Portal hypertension, Portal Hypertension: If you review the portal cir...

Portal Hypertension: If you review the portal circulation you may recall that normal blood flow to and from the liver depends on proper functioning of  the portal vein, the he

Explain the steps of exercise, Explain the Steps of Exercise You have l...

Explain the Steps of Exercise You have learnt the steps of exercises in Block 3, Unit 1 of theory block. Let us review the steps. In aerobic exercises one has to under go fo

What is acute massive pulmonary embolism, what is Acute Massive Pulmonary E...

what is Acute Massive Pulmonary Embolism ? Acute Massive Pulmonary Embolism :  Before the era of open-heart surgery, Trendelenburg (1908) described technique of open p

Procedures for diagnosis - electron microscopy, Direct demonstration of the...

Direct demonstration of the causative agent by electron microscopy (EM): Where facilities for electron microscopy are available and a viral disease is suspected, presence o

Name the two groups of nephrons, Name the two groups of nephrons on the bas...

Name the two groups of nephrons on the basis of their position in the kidney. How are they different from each other? a) How is the halophyte Rhizophora adapted to survive in i

Membrane with the intention of delimits the nucleus, Q What is the name of ...

Q What is the name of the membrane with the intention of delimits the nucleus? To which component of the cell structure is that membrane contiguous? The nuclear membrane is als

Describe occurs from a physiological standpoint, Describe the occurs from a...

Describe the occurs from a physiological standpoint to the respiratory system when smoke is inhaled and exhaled. You will need to use other sources aside from your textbook.

Artificial skin, Artificial Skin: The skin generated in vitro is in fac...

Artificial Skin: The skin generated in vitro is in fact the epidermis portion of skin only; when the epidermis is applied to the burnt part, this leads to the regeneration of d

Define the remodeling rate, Q. Define the Remodeling rate? Human corti...

Q. Define the Remodeling rate? Human cortical bone: 2-10%  per year depending on site and age of patient. Trabecular bone: Higher turnover rate 20-30% per year. In a stu

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