AQA GCSE Combined Science Foundation (8464), Foundation tier · Biology › Inheritance, variation and evolution
Practise Classification of living organisms. 7 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
How living things are classified: the Linnaean system (kingdom down to species), the binomial naming system, Carl Woese's three-domain system and evolutionary trees. Expect recall of the order of groups, questions using scientific names, and interpreting evolutionary trees.
Key facts
Linnaeus: kingdom, phylum, class, order, family, genus, species
Classified by structure and characteristics
Binomial name = genus + species, e.g. Homo sapiens
Carl Woese's three domains (from chemical analysis): archaea, bacteria, eukaryota
Archaea = primitive bacteria, usually in extreme environments
Eukaryota = protists, fungi, plants and animals
Evolutionary tree: branch point = common ancestor; most recent common ancestor = most closely related
Classification changed because of better microscopes and better understanding of biochemical processes
Notes
The Linnaean system
diagram
Traditionally, living things have been classified into groups depending on their structure and characteristics, in a system developed by Carl Linnaeus.
Linnaeus classified living things into kingdom, phylum, class, order, family, genus and species.
Going down from kingdom to species, each group contains fewer organisms, which are more similar to each other.
Organisms are named by the binomial system of genus and species, e.g. Homo sapiens for humans. The genus starts with a capital letter; the species name does not.
Two organisms in the same genus are more closely related than two organisms that are only in the same family.
The Linnaean system, using the grey wolf as an example.
The three-domain system
diagram
As microscopes improved, scientists could see internal structures in more detail, and understanding of biochemical processes progressed. New models of classification were proposed.
Evidence from chemical analysis led Carl Woese to develop the three-domain system.
Archaea: primitive bacteria, usually living in extreme environments (e.g. hot springs or very salty lakes).
Bacteria: true bacteria.
Eukaryota: includes protists, fungi, plants and animals.
The three domains. Archaea and eukaryota share a more recent common ancestor.
Evolutionary trees
Evolutionary trees are a method used by scientists to show how they believe organisms are related.
They use current classification data for living organisms and fossil data for extinct organisms.
Each branch point is a common ancestor. The more recent the common ancestor, the more closely related the organisms are.
How to answer each type of question
Use the Linnaean system and binomial names
1 to 3 marksGrade 4
Learn the order from kingdom (largest group) to species (smallest).
In a binomial name, the first word is the genus and the second is the species.
Example. The scientific name of the grey wolf is Canis lupus. The scientific name of the coyote is Canis latrans. (a) Give the genus of the grey wolf. (b) What do the names show about how closely related the grey wolf and the coyote are? [2 marks]
Show the model answerHide the model answer
(a) Canis (1) (b) They are in the same genus, so they are closely related, but they are different species (1)
Don’t lose marks
Putting the groups in the wrong order, especially swapping class and order, or family and genus.
Writing the species name first, or giving the genus a small letter.
Saying archaea are true bacteria. Archaea are primitive bacteria usually found in extreme environments; true bacteria are a separate domain.
Saying that one living organism on an evolutionary tree evolved from another, when they share a common ancestor.
More tips
Memory tricks
'King Philip Came Over For Good Soup': kingdom, phylum, class, order, family, genus, species.
Binomial = two names: Genus (capital letter) then species (small letter).
Three domains, 'ABE': Archaea, Bacteria, Eukaryota.
Exam technique
In evolutionary tree questions, identify the common ancestor and give its time from the tree.
Learn who did what: Linnaeus (kingdom to species, binomial names) and Woese (three domains).
Use the phrase 'chemical analysis' for the evidence behind the three-domain system.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
List the Linnaean groups in orderKingdom, phylum, class, order, family, genus, species.
Grade 4
Use binomial namesAn organism's scientific name is its genus followed by its species, e.g. Homo sapiens.
Grade 5
Describe how Linnaeus classified organismsInto groups depending on their structure and characteristics.
Grade 5
Name the three domainsArchaea, bacteria and eukaryota.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
In 1990, Carl Woese proposed a new system of classification called the three-domain system. Which domain contains fungi, plants and animals?
Eukaryota
Write these groups in order, from the largest group to the smallest. class · family · genus · kingdom · order · phylum · species
kingdom, phylum, class, order, family, genus, species
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Carl Linnaeus developed a system for classifying living things into groups.
(a) Write these groups in order, from the largest group to the smallest. class · family · genus · kingdom · order · phylum · species[2]
(b) Complete the sentence. In the binomial system, the first part of an organism’s name is its ....................... and the second part is its ....................... .[2]
(c) Which scientist developed the three-domain system of classification? Tick (✓) one box.[1]
Charles Darwin
Carl Linnaeus
Gregor Mendel
Carl Woese
Show the answer and mark scheme
(a)Answer: kingdom, phylum, class, order, family, genus, species
kingdom, phylum, class at the start (in that order)
order, family, genus, species at the end (in that order)
(b)Answer: genus; species
genus
species
(c)Answer: Carl Woese
Question 2Medium6 marks
In 1990, Carl Woese proposed a new system of classification called the three-domain system.
(a) Which domain contains fungi, plants and animals?[1]
(b) One domain contains primitive bacteria that usually live in extreme environments. Name this domain.[1]
(c) The three-domain system was developed using evidence from chemical analysis. Explain why this evidence led to a change in the classification system.[2]
(d) Explain how improvements in microscopes affected the classification of living things.[2]
Show the answer and mark scheme
(a)Answer: Eukaryota
eukaryota / eukaryotes
(b)Answer: Archaea
archaea
(c)
chemical analysis showed that archaea are very different from (true) bacteria / organisms that look similar may not be closely related
(so) they were placed in a separate group / domain / the old system did not show how closely organisms are related
(d)
better microscopes showed the internal structures / details of cells
(so) organisms could be grouped using more features / new classification models were proposed / some organisms were reclassified
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