Classifying and naming living things Cambridge IGCSE Biology (9–1) revision
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In plain words
There are millions of kinds of living thing, so biologists sort them into groups that share features, the way a library sorts books. Every kind gets a two-part scientific name that is the same in every language: humans are Homo sapiens.
Three things to know
- A species is a group of organisms that can reproduce together to produce fertile offspring.
- The binomial system gives each species two names: the genus first (with a capital letter), then the species. Homo sapiens: genus Homo, species sapiens.
- Organisms that share more features, and more of the same DNA base sequences, are more closely related. A dichotomous key identifies an organism by asking a series of either/or questions.
Tips and tricks
- Fertile is the important word in the definition of a species. A horse and a donkey can produce a mule, but mules can't have young.
- In a binomial name the genus comes first and has the capital letter.
It lands in your notebook with its questions as flashcards.
Classifying and naming living things: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is a species?
Being able to produce fertile young is what defines it.
In the name Homo sapiens, what is Homo?
The genus is the first of the two names.
Two organisms have very similar DNA base sequences. What does this suggest?
The more DNA they share, the more recent their common ancestor.
What does a dichotomous key do?
Each step gives two choices, and you follow the one that fits.
Which name is written correctly in the binomial system?
Genus first with a capital letter, then the species in lower case.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 6 marks. Write your answers on paper, then check them.
Classifying and naming living things
Cambridge IGCSE Biology (9–1) 0970 · 6 marks · papermunch.org
Name ______________________________ Date ______________
State what is meant by a species.[2]
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A group of organisms that can reproduce with each other to produce fertile offspring.
The lion is Panthera leo and the tiger is Panthera tigris. State what these names show about lions and tigers.[2]
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They are in the same genus (Panthera), so they are closely related, but they are different species.
Describe how a dichotomous key is used to identify an organism.[2]
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Start at the first pair of statements, choose the one that fits the organism, and follow where it leads. Repeat until you reach a name.
Answers: Classifying and naming living things
- 1. A group of organisms that can reproduce with each other to produce fertile offspring.
- 2. They are in the same genus (Panthera), so they are closely related, but they are different species.
- 3. Start at the first pair of statements, choose the one that fits the organism, and follow where it leads. Repeat until you reach a name.