A scientific name is a two-part Latin name that is used for a species all over the world. The first part, the genus, tells you which group of closely related species it belongs to. The second part, the species name, identifies the particular species. This lesson belongs with living systems and classification and is tested with short, exact questions.
How is a binomial name written?
Write the genus first with a capital letter. Write the species with a lower-case letter. Italicise in print, and underline each part separately if you write by hand.
For example, humans are Homo sapiens. Homo is the genus and sapiens is the species. The species word on its own is not a full name, because the same species word can be used in different genera.
The classification hierarchy runs from large to small: kingdom, phylum, class, order, family, genus, species. Check the current syllabus to see how much of this list you are expected to know.
Why can common names mislead?
Common names are built from everyday impressions. A jellyfish is not a fish, and a starfish is not a fish. A word shared by two common names does not show that the organisms are closely related.
Scientific names follow rules that scientists agree on, so they are the same in every country and language. That is why an exam will often use one.
Worked example
Three trees have these scientific names (real species, used here only as examples of the naming pattern):
- Quercus robur
- Quercus alba
- Acer rubrum
Question: Which two are most closely related? Explain.
Step 1, identify the genus of each. The genera are Quercus, Quercus and Acer.
Step 2, compare. The first two share the genus Quercus. The third has a different genus.
Step 3, answer. Quercus robur and Quercus alba are most closely related, because they are in the same genus.
Check: the question does not ask about the common names, and the answer does not rely on them.
The mistake to watch for
Mistaken answer: “Quercus robur and Acer rubrum are related because they are both trees and both have red in the name.”
The student compared the common names and the general look of the organisms, not the genus.
The correction is to compare the genus first. Do not use a colour, a size or a habitat as evidence of relatedness. Also watch the writing: Quercus Robur and quercus robur both lose marks.
Check yourself
1. Write the binomial name of the lion, Panthera leo, with correct capital letters, and state the genus.
Show answer
Panthera leo. The genus is Panthera, with a capital P.
2. Panthera leo and Panthera tigris are two species. What does their name tell you about how closely related they are?
Show answer
They share the same genus, Panthera, so they are closely related and share many features.
3. A student says a silverfish must be a fish because of its name. Give a one-sentence reply.
Show answer
Common names can mislead, and relatedness is judged from features and scientific classification, not from a word in an everyday name.
Where this leads next
Names are one piece of the picture, and the next lesson moves from organisms to something that is not a cell at all: comparing virus and cell descriptions. To review how groups are built first, read explaining classification by shared features.
Marks on this topic can depend on exact wording. A teacher in online one-to-one Biology tuition can mark the wording of your own written answers with you.