Download Classification of Living Things

Classification of Living Things
Classification is the process of sorting things into groups, based on how they are alike and
different. Biologists use classification to organize living things into groups. Living things that are
classified together have similar characteristics. This makes them easier to identify and study.
As scientists classify, they keep dividing the organisms into smaller and smaller groups. This is
called taxonomy. Today, there are 8 groups of classification. From biggest to smallest, they are:
Domain------Kingdom------Phylum------Class------Order-------Family-------Genus------Species
In 6th grade, we will only learn about the two largest groups – Domains and Kingdoms.
THE THREE DOMAINS
The broadest (biggest) category of classification is the Domain. There are 3 Domains. Every
organism on Earth is classified into one of the three Domains.
Archae is one of the two domains that include bacteria. All organisms in the Archae domain are
prokaryotic (cells do not have a nucleus.) Approximately 4% of all organisms are in the Archae
domain. Archae bacteria are special because they live in extreme environments, such as in hot
springs and volcanic vents. Other bacteria cannot live in such extreme environments. This
extreme environment is what separates Archae bacteria from other bacteria.
Eubacteria is the domain that all other bacteria are classified under. Approximately 7% of all
organisms are Eubacteria. These bacteria are more “normal’ bacteria, that cannot survive in
extreme environments. Eubacteria live in moderate climates. These organisms are prokaryotic,
because their cells do not have a nucleus. Scientists estimate that there are about 1 million types
of bacteria, but we have only identified about 4,000 of them.
Eukarya is the domain that includes all eukaryotic organisms. Remember, eukaryotes are
organisms whose cells have a nucleus to hold the DNA. Approximately 89% of all organisms are
eukaryotes. In the Eukarya domain, there are about 12.4 million species. These species include
plants, animals, fungi, and protists.
THE SIX KINGDOMS
After organisms are classified into Domains, they are divided again into Kingdoms. A Kingdom is
smaller than a Domain. The Archae and Eubacteria Domains each have one Kingdom. The
Eukarya Domain has four Kingdoms.
To classify organisms into Kingdoms, scientists use the 4 characteristics we learned about:
 Cell Type (prokaryotic or eukaryotic)
 Number of Cells (unicellular or multicellular)
 How the Organism Gets Energy (autotroph or heterotroph)
 How the Organism Reproduces (asexual or sexual)
The Archaebacteria kingdom is the only kingdom in the Archae Domain. Archaebacteria are
unicellular prokaryotes that live in extreme environments such as hot springs and volcanic vents.
They can be either autotrophs or heterotrophs. Archaebacteria always reproduce asexually.
Examples of archaebacteria include thermophiles and halophiles (both are types of bacteria).
The Eubacteria kingdom is the only kingdom in the Eubacteria Domain. Eubacteria are
unicellular prokaryotes that live in moderate environments. Some eubacteria are autotrophs,
while others are heterotrophs. Eubacteria reproduce asexually. Examples include bacteria in
yogurt, which is helpful, as well as E.Coli or Salmonella, which can be dangerous to humans.
Some eubacteria are decomposers, which helps clean up the environment.
The Protist kingdom is one of the four kingdoms in the Eukarya Domain. Protists are unicellular
eukaryotes (cells have a nucleus) that are found in pond water. Because they are unicellular,
these organisms are microscopic and usually cannot be seen with just your eyes. Protists can be
autotrophs or heterotrophs. Some protists reproduce asexually, while others reproduce sexually.
Examples of protists include amoeba, diatoms, and paramecium.
The Fungus Kingdom is the second of the four kingdoms in the Eukarya Domain. Fungi include
organisms such as mushrooms, mold, and yeast. All fungi are multicellular eukaryotes (cells
have a nucleus). They are heterotrophs that get food by decomposing (or breaking down) dead
organisms. Some fungi reproduce asexually, while others reproduce sexually.
The Plant kingdom is the third kingdom in the Eukarya Domain. All plants are multicellular,
eukaryotic organisms. Plants are autotrophs – they make their own food by photosynthesis.
Plants reproduce sexually. Examples of plants are grass, trees, cactus, and seaweed.
The Animal Kingdom is the fourth kingdom in the Eukarya Domain. All animals are eukaryotes,
and all are multicellular. Animals are heterotrophs – they get their food by eating other organisms,
or occasionally by decomposing dead organisms. Animals reproduce sexually. Examples of
animals are horses, jellyfish, butterflies, and frogs.