The Seven Kingdoms

Archaebacteria

Archaebacteria are single celled organisms. They are prokaryotes that live in extreme environments on earth. They live in areas with extremely high temperaure or acidity.14_7.gif Most eat small nutrients or convert to get energy. Some survive without oxygen.
They are divided into three main groups.
Methanogens- Convert Co2 and H2 into methane gas to make energy. They survive without oxygen.
Halophiles- Live in areas with ridiculously high salt content.
Thermoacidophiles- Thrive in areas with high acidity and temperature, lethal to most other organisms.
They have all have a unique cell wall and a plasma membrane, which is able to filter incoming substances.

http://www.pinkmonkey.com/studyguides/subjects/biology-edited/chap14/14_7.gif://230nsc1.phy-astr.gsu.edu/hbase/biology/prokar.html#c4Eubacteria

Eubacteria

Eubacteria make up most of the bacteria in the world. They are singlecelled prokaryotes that live almost anywhere on the earth. Both with or without oxygen respiratory systems exist in Eubacteria. They take in carbon in many ways like photosynthesis for example, while others convert nitrogen.
Their functions keep many ecosystems in balance wether it is carbon intake of nitrogen conversion. An example of this is the nodules in plants where anaerobic bacteria can live while the provide nitrogen to the plants.
They are divided into to main sets, Gram Positive or Negative. This is based on the Gram test which factors in the amounts Peptidoglycan in the cell.
Then there are many different kinds of Eubacteria like gliding, Gram-positive and negative cocci, and rickettsias.

http://faculty.plattsburgh.edu/neil.buckley/Concepts%20in%20Biology/Lecture6DomainsandKingdoms.htm

Protista

Kingdom Protista nicknamed the "catch all group" is different from most kingdoms. This is because it is made up of left over organisms that don't share any common traits. Protists come in a huge variety. Most of them or single celled organisms but some like seaweed are multicellular. They differ in every aspect from energy intake to reparatory system. They are Eukaryotes.
One interesting thing is Kingdom Protista is made up of many organisms that were previously classified as plants or animals, like protozoans. The protists are main components to the food chain in their diversity.
L8D1_clip_image006.jpghttp://www.rpdp.net/sciencetips_v3/images/l8d1/L8D1_clip_image006.jpg
As you can see protists can be very different.