Classification places an organism in nested groups. Each level down has fewer organisms that share more features.
This lesson is part of biodiversity in the SPM Biology subject guide. Once you can place organisms, continue with dichotomous keys.
What is the order of the levels?
From broad to narrow: kingdom, phylum, class, order, family, genus, species.
Think of a set of boxes. Each box sits inside a bigger one, so every species belongs to one genus, every genus to one family, and so on upward.
As you go down, the number of organisms in the group falls, and the number of features they share rises.
Worked example: placing one organism
Here is an original placement of the Malayan tiger.
| Level | Group | Feature used |
|---|---|---|
| Kingdom | Animalia | Multicellular, feeds on other organisms |
| Phylum | Chordata | Has a backbone (vertebrate) |
| Class | Mammalia | Fur, feeds young with milk |
| Order | Carnivora | Meat-eating teeth adapted for killing prey |
| Family | Felidae | Cats |
| Genus | Panthera | Big cats |
| Species | Panthera tigris | Tiger |
Read the table downward: each row is a smaller group inside the row above. The feature in the last column is the reason the organism sits there.
How to write the scientific name
The name has two parts, genus first and species second.
| Format | Status |
|---|---|
| Panthera tigris (italic or underlined separately) | Correct |
| panthera Tigris | Wrong: capital letters reversed |
| Panthera Tigris | Wrong: species must be lower case |
| Tigris | Wrong: the species name alone is not enough |
In handwriting, underline each word separately: Panthera tigris.
A common mistake: swapping class and order
The two levels sit next to each other, so they are easy to swap. Class is the bigger group, and order sits inside it.
A reliable check: ask whether the group name still describes many different animals (class) or a narrower type (order). Mammalia covers bats, whales and tigers. Carnivora is narrower.
Check yourself
An organism is placed in the genus Hibiscus and the species rosa-sinensis (the hibiscus flower, Malaysia’s national flower). Write its scientific name correctly. Which level is larger, genus or family?
Answer
Hibiscus rosa-sinensis. Genus with a capital, species in lower case, both underlined separately if handwritten.
Family is larger than genus, because one family contains one or more genera.
If you wrote the species with a capital letter, check the format table above.
What to study next
Go to constructing and using dichotomous keys, then log any order slips in a mistake log.
If you want a teacher to drill your placement routine, see online one-to-one Biology tuition.