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Classification of Living Things

11 min read

Why classify?

There are millions of kinds of living things. Classification puts them into groups according to the features they share. It makes them easier to study, name and identify, and it shows how they are related.

From biggest group to smallest
LevelExample: lion
KingdomAnimalia
PhylumChordata
ClassMammalia
OrderCarnivora
FamilyFelidae
GenusPanthera
SpeciesPanthera leo
Levels of classificationA funnel of seven levels from the biggest group, kingdom, down to the smallest, species. The lion is used as an example at every level: Animalia, Chordata, Mammalia, Carnivora, Felidae, Panthera, Panthera leo.KingdomAnimaliaPhylumChordataClassMammaliaOrderCarnivoraFamilyFelidaeGenusPantheraSpeciesPanthera leo (lion)Example: the lion

The five kingdoms

KingdomCellsFeedingExamples
Monerano nucleus (prokaryotes)variedbacteria
Protoctista (Protista)single cell or simplevariedamoeba, Plasmodium
Fungicell wall of chitinfeed on dead or living mattermushroom, yeast, mould
Plantaecell wall of cellulose, chloroplastsmake their own foodmaize, mango
Animaliano cell wallfeed on other organismsfish, birds, humans
The five kingdomsFive coloured boxes naming the five kingdoms of living things with an example of each: Monera such as bacteria, Protoctista such as amoeba and algae, Fungi such as mushrooms and yeast, Plantae such as maize, and Animalia such as fish, birds and humans.MonerabacteriaProtoctistaamoeba, algaeFungimushroom, yeastPlantaemaize, mango treeAnimaliafish, bird, humanLiving things are sorted into five kingdoms
Try itCompare two groups

Each group has a number of features. Change how many features plants have, how many animals have, and how many they share. The overlap shows the features common to both.

A dichotomous key is a set of paired questions with yes or no answers. Start at the top, answer the question about the organism in front of you and follow the branch. Each question splits the group in two until you reach a name.

A dichotomous keyA branching key that sorts four animals by yes or no questions: does it have legs, does it have six legs, does it have wings. The answers lead to snake, spider, butterfly or ant.Does it have legs?noyesSnakeDoes it have 6 legs?noyesSpiderDoes it have wings?noyes
A key that sorts four animals: snake, spider, butterfly and ant.
Check yourself Which is the correct scientific name format?
Check yourself Which kingdom has cells with cell walls and chloroplasts?

Key terms

Classification
Sorting living things into groups by shared features.
Species
A group that can breed together and produce fertile young.
Kingdom
The largest group in classification.
Binomial name
A two-part scientific name: genus and species.

Summary

  • Classification groups organisms by shared features.
  • Seven levels from kingdom to species; the five kingdoms are Monera, Protoctista, Fungi, Plantae and Animalia.
  • A dichotomous key identifies an organism through a series of yes/no choices.
Cell Structure and Organisation