BIOLOGY ASSIGNMENTPresented By

THE EINSTEINS

STD:9th 2012-13

TOPI

C:

ELEC

TRON M

ICROSC

OPE

&

EUKA

RYOTI

C ; P

ROKARY

OTIC C

ELLS

INDEX.WHAT IS ELECTRON MICROSCOPE?

.INVENTORS.EUKARYOTIC CELLS .PROKARYOTIC CELLS

.DIFFERENCE BETWEEN THEM

The electron microscope is a significant improvement over the optical (light) microscope. The optical microscope is only able to focus in on objects that are at least the size of a wavelength of light. An electron microscope, in contrast, can magnify images thousands of times smaller than the wavelength of light.

WHAT IS AN ELECTRON MICROSCOPE?

The Electron Microscope is a huge structure which makes use of electromagnets for magnification & a beam of electrons for illumination of the object . This requires internal vacuum in the chamber.

The magnification achieved is 2,000,000, times

inventors

Max Knoll & Ernst Ruska made the first Electron Microscope in the year 1928 which could magnify 17 times .They further improved it to give 400 times magnification in 1932

Hiller James in 1937 made an improved version of the Electron Microscope with a Magnification of 7000.times

Vladimir Zworykin a Russian born American Scientist developed an Electron Microscope which could give 2 Million times Magnification – This is astonishingly 50 times more than the magnification achieved by a light microscope.

Eukaryote is a cell which is a complex structure enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear envelope, within which the genetic material is carried. The presence of a nucleus gives eukaryotes their name, which comes from the Greek ευ (eu, "good") and κάρυον (karyon, "nut" or "kernel"). Most eukaryotic cells also contain other membrane-bound organelles such as mitochondria, chloroplasts and the Golgi apparatus. All species of large complex organisms are eukaryotes, including animals, plants and fungi,.

EUKARYOTIC CELLS

Cells that lack a membrane-bound nucleus are called prokaryotes (from the Greek meaning before nuclei). These cells have few internal structures that are distinguishable under a microscope. Cells in the monera kingdom such as bacteria and cyanobacteria (also known as blue-green algae) are prokaryotes.

PROKARYOTIC CELLS

Prokaryotes

They are primitive , incomplete cells

They lack a nucleus ,but nuclear matter lies free in the cytoplasm & is called nucleoid

Membrane bound cell organelles are absent

Reproduction takes place by the process of fission & budding

Eukaryotes

They are advanced , complete cells

Nucleus is present & is enveloped by a double membrane

Membrane bound cell organelles are present

Reproduction takes place by the process of miosys & mitosys.

DIFFERENCES BETWEEN THEM

Thank You