Biology Task 1

 Prokaryotes and Eukaryotes

Prokaryotes

- The prokaryotes are a group of organisms that lack a cell nucleus or any other membrane-bound organelles. They were originally thought to live on in inhospitable conditions but have since been found in all types of habitats.

- The word PROKARYOTES comes from Greek.

- Prokaryotes live in nearly all environments on earth where there is liquid water.

- They are cells in bacteria and archaea and cells are usually independent.

- The oldest known prokaryotes were laid down approximately 3.5 billion years ago, only about 1 billion years after the formation of the Earth's crust.

- Prokaryotes have diversified greatly throughout their long existence. The metabolism of prokaryotes is far more varied than that of eukaryotes, leading too many highly distinct prokaryotic types.

Cell structure of a bactarium, one of the two domains of prokaryotic life.

 

Eukaryotes

- A eukaryote is an organism whose cells contain complex structures enclosed within membrane.

- All species of large complex organisms are eukaryotes (including animals, plants, fungi and protists).

- The word EUKARYOTES also comes from Greek.

- The eukaryotic cells are often found in multicellular organisms.

- The origin of the eukaryotic cell was a milestone in the evolution of life, since they include all complex cells and almost all multi-cellular organisms.

- The presence of steranes indicates that eukaryotes were present 2.7 billion years ago.

Structure of a typical plant cell (eukaryote)

Structure of a typical animal cell (eukaryote)

 

In the world of cells, there are two major groups: the prokaryotes and the eukaryotes. They are very similar in that they contain many of the same parts. However, there are a few major differences between them.

	Prokaryote	Eukaryotic Eukaryote
Size of cell	Very minute in size,  between 1-10  micrometers	Fairly large in size, animal cells are between 10-30 micrometers; most plant cells are between 10-100 micrometers
Nucleus	Do not have a nucleus	True nucleus
Membrane-enclosed organelles	Absent	Present
Flagella	Consist of two protein building blocks	Complex: consists of multiple microtubules
Cilia	Complex	Simple
Cell Wall	Usually present	Present in animals, not present in plants
Plasma membrane	No carbohydrates and lacks sterols	Sterols and carbohydrates present that serve as receptors
Cytoplasm	No cytoskeleton	Cytoskeleton with cytoplasmic
Ribosomes	Smaller size	Large size except in organelles when smaller
Chromosome	Single chromosome present	More than one chromosome present
Cell division	By fission or budding	By mitosis or meiosis
Sexual reproduction	Transfer of DNA fragments only and is always asexual	Involves meiosis and is asexual or sexual
Metabolic	Huge of metabolic pathways	Common metabolic pathways
Endoplasmic reticulum	Absent	Present

Differences between Prokaryote and Eukaryote

source: http://www.daviddarling.info/encyclopedia/E/eukarycell.html
http://en.wikipedia.org/wiki/Cell_%28biology%29
http://en.wikipedia.org/wiki/Eukaryote
http://en.wikipedia.org/wiki/Prokaryote
http://www.allfreeessays.com/essays/Evolutionary-Relationship-Between-Prokaryotic-Eukaryotic-Cells/2603.html
http://intranet.canacad.ac.jp:3445/bioibsl1/4424

http://www.youtube.com/watch?v=nP9lZG94DO0