Why Classify Living Things?
Because there are sooooo many living
organisms. We have identified 2,500,000
living things and there are an estimated
20,000,000 species on earth.
To give each organism a scientific name.
Each organism is given a universal name
so it can be recognized in any language.
Who Started Classification?
Several scientists came up with their own
ideas for how to group and name
Carolus Linnaeus (1707-1778) developed
binomial nomenclature which is still used
Binomial nomenclature gives each organism
a 2-part name in Latin.
Human = Homo sapiens
Dog = Canis familiaris
Cat = Felis catus
Tiger = Panthera tigris
Jaguar = Panthera onca
How are Living Things Classified?
Taxonomy – assigning organisms into
Categories – Kingdom (largest) phylum
(division for plants) class order
family genus species (smallest)
Definition of species = similar
characteristics, can interbreed
Classification of Humans
Levels of Classification
The more closely related 2 species are, the more
levels they have in common.
Closely related species shared a more recent
The level of relatedness between 2 species is
- physical characteristics
- reproductive strategies
- way of life
- DNA comparisons (more related = fewer
differences in genetic code)
How many kingdoms are there?
Linnaeus said two – plants and animals
5 Kingdom System
Now we use 6 Kingdoms!