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 do you mean by synapses, Q. What do you mean by synapses? Synapses...

Q. What do you mean by synapses? Synapses are the structures that transmit the neural impulse between two neurons. When the electric impulse arrives the presynaptic membrane

What is the prevailing wind direction, what is the prevailing wind directio...

what is the prevailing wind direction in equatorial regions affected by the trade winds? a) The wind blows from east to west b) the wind blows from west to east

Name the hormone that makes the plants more tolerant, In humans, starch dig...

In humans, starch digestion begins in the buccal cavity but stops in the Stomach. Why? Name the two most biodiversity-rich zones of India. Name the hormone that makes the p

Endocrine glands, Endocrine glands Endocrine glands have no ducts - ...

Endocrine glands Endocrine glands have no ducts - so these are also called as ductless glands Eg.Pituitary etc., These glands secrete chemical substances called HORMONES

How different are birds and reptiles, Q. How different are birds and reptil...

Q. How different are birds and reptiles concerning the maintenance of body temperature? Are birds rare in polar regions? Reptiles are heterothermic that is they do not control

Explain risk factors and their role in cad, Explain risk factors and their ...

Explain risk factors and their role in cad ? The concept of risk factors constitutes a major advance for developing strategies to prevent CVD. The Framingham Heat Study played

Nutrition, Nutrition As we have said earlier all animals are heterotro...

Nutrition As we have said earlier all animals are heterotrophs and require food from the environment. What is this food made up of? If the food of a number of different animal

Determine the groups of soil organisms, Determine the groups of soil organi...

Determine the groups of soil organisms The soil organisms are classified into two broad groups viz. soil flora (related to plants) and soil fauna (related to animals) which ar

Person and being, What evidence is there that makes it seem humans have mor...

What evidence is there that makes it seem humans have more than a material existence?

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