Classification
Prokaryotes and Eukaryotes
Domains and Kingdoms
•Today, a three-domain system of classification iscommonly used.
•The three domains are Bacteria, Archaea, andEukarya.
•Within the domains are kingdoms.
•Organisms are placed into domains and kingdomsbased on their cell type, their ability to make food,and the number of cells in their bodies.
Bacteria
•Members of the domain Bacteria are prokaryotes.
•Prokaryotes are organisms whose cells lack a nucleus. Anucleus is a dense area in a cell that contains nucleicacids – the chemical instructions that direct the cell’sactivities.
•In prokaryotes, nucleic acids are scattered throughoutthe cell.
•The cell wall is the target for antibiotics, as well as forcarbohydrates that our immune system uses to detectinfection.
Bacteria
•Prokaryotic cells may have photosynthetic pigments.
•Some have an external whip-like flagella forlocomotion or hair like pili for adhesion.
•Prokaryotic cells come in multiple shapes: cocci(round), baccilli (rods), and spirilla or spirochetes(helical cells).
Bacteria Cell Shapes
Prokaryotic Cell
Archaea
•Members of the domain Archaea, whose name comes fromthe Greek word for “ancient”, can be found in some of themost extreme environments on Earth, including hot springs,very salty water, swamps, and the intestines of cows.
•Scientists think that the harsh conditions in which archaea liveare similar to those of ancient Earth.
•Like bacteria, some archea are unicellular prokaryotypes andsome are autotrophs while others are heterotrophs.
•Although bacteria and archaea are similar in some ways, thereare important differences in the structure and chemical make-up of their cells.
Eukarya
•Members of the domain Eukarya are eukaryotes –organisms with cells that contain nuclei.
•Scientists classify organisms in the domain Eukarya intoone of four kingdoms: plants, animals, protists, andfungi.
•Plants are all multicellular eukaryotes. In general, plantsare autotrophs and feed almost all of the heterotrophson land.
•Animals are multicellular eukaryotes. All animals areheterotrophs. Animals have different adaptations thatallow them to find food, capture it, eat it, and digest it.
Protists
•Slime molds are protists. The protist kingdom issometimes called the “odds and ends” kingdombecause its members are so different from oneanother.
•Protists can be autotrophs or heterotrophs.
•Although many protists are unicellular, some, such asseaweeds, are multicellular.
Protists
Fungi
•Mushrooms, molds, mildew, and yeast are all fungi.
•Most fungi are multicellular eukaryoes.
•A few, such as yeast, are unicellular eukaryotes.
•Fungi are found almost everywhere on land, but only afew live in fresh water.
•All fungi are heterotrophs. Most fungi feed by absorbingnutrients from dead or decaying organisms.
Prokaryotic vs Eukaryotic
•The difference between prokaryotic and eukaryotic isconsidered to be the most important distinctionamong groups of organisms. Eukaryotic cells containmembrane-bound organelles, such as the nucleus,while prokaryotic cells do not.
•Prokaryotes were the only form of life on Earth formillions of years until more complicated eukaryoticcells came into being.
Prokaryotes vs Eukaryotes
