cells

• The cellular world is divided into two major groups based on whether or not the cells have a nucleus. (Prokaryote and Eukaryote)
• Prokaryotes that include all bacteria divided into two groups—the archaebacteria and the eubacteria—diverged early in evolution.​

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  Some archaebacteria are extremophils (live in extreme environments) which unusual today but may have been prevalent in primitive Earth. 
• Eubacteria include common forms of present-day bacteria—a large group of organisms living in a wide range of environments (soil, water, and other organisms e.g., human pathogens). ​

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  Spherical, rod-shaped, or spiral, with diameters of 1 to 10 μm. ​

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  DNA contents range from .ca 0.6 million to 5 million base pairs, sufficient to encode about 5000 different proteins.​

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  The largest and most complex prokaryotes are the cyanobacteria, bacteria in which photosynthesis evolved.​
• Eukaryotic cells are complex cells , and include all animals and plants cells . They contain a nucleus
• Prokaryotic cells are smaller and simpler , they include Bacteria . They do not contain a nucleus
• Organelles are tiny structures that can be found wihtin the cell . You can only see them if you use a microscope
• Some of the organelles found in a typical animal cell/

  • Nucleus : an organelle which contains the genetic material that controls the cell's activities. It is surrounded by its own membrane