AQA GCSE Biology - 6.4 Classification of Living Organisms - Linnaeus Classification and Evolutionary Trees

Sep 5, 2026

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GCSE Biology 6.4 explains how living organisms are classified into groups using shared features and scientific naming. It covers the Linnaeus classification system, including binomial nomenclature and the sequence Kingdom to Species, plus a mnemonic for memorising the order. The development of classification is traced from morphology and anatomy to DNA sequencing, showing how genetic similarity indicates relatedness. It also introduces the three-domain system and explains how evolutionary trees depict speciation and common ancestry.

LanguageEnglish

CategoryExam

FormatPDF

Pages6

Reading Time15 min

AccessFree to download

6.4.1 Classification

Classification

Linnaeus’s system of classification

Development of Classification

Three Domain System

Evolutionary Trees

Head to www.savemyexams. com for more awesome resources AQA GCSE Biology: Combined Science 6 .4 Classification of Living Organisms Contents 6.4.1 Classification Page 1 of 6 © 2015 − 2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources 6.4.1 Classification Linnaeus Classification There are millions of species of organisms on Earth A species is defined as a group of organisms that can reproduce to produce fertile offspring These species can be classified into groups by the features that they share eg. all mammals have bodies covered in hair, feed young from mammary glands and have external ears (pinnas) Traditionally living things have been classified into groups depending on their structure and characteristics in a system developed by Carl Linnaeus. Organisms were first classified by a Swedish naturalist called Linnaeus in away that allows the subdivision of living organisms into smaller and more specialised groups The species in these groups have more and more features in common the more subdivided they get He named organisms in Latin using the binomial system where the scientific name of an organism is made up of two parts starting with the genus (always given a capital letter) and followed by the species (starting with a lower case letter) When typed binomial names are always in italics (which indicates they are Latin) e. g. Homo sapiens The sequence of classification is: Kingdom, Phylum, Class, Order, Family, Genus, Species Page 2 of 6 © 2015 − 2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources Linnaeus’s system of classification Examiner Tip The order of classification can be remembered by using a mnemonic like: KING PHILIP CAME OVER FOR GRAN’S SPAGHETTI Page 3 of 6 © 2015 − 2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources Development of Classification Organisms share features because they originally descend from a common ancestor Example: all mammals have bodies covered in hair, feed young from mammary glands and have external ears (pinnas) Originally, organisms were classified using morphology (the overall form and shape of the organism, e. g. whether it had wings or legs) and anatomy (the detailed body structure as determined by dissection) As evidence of internal structures became more developed due to improvements in microscopes, and the understanding of biochemical processes progressed, new models of classification were proposed As technology advanced, DNA sequencing allowed us to classify organisms using a more scientific approach Studies of DNA sequences of different species show that the more similar the base sequences in the DNA of two species, the more closely related those two species are (and the more recent in time their common ancestor is) This means that the base sequences in a mammal’s DNA are more closely related to all other mammals than to any other vertebrate groups DNA sequences can show how closely related different species are The sequences above show that Brachinus armiger and Brachinushirsutus are more closely related than any other species in the list as their DNA sequences are identical except for the last but one base (B.armiger has aT in that position whereas B.hirsutus has anA) As DNA base sequences are used to code for amino acid sequences in proteins, the similarities in amino acid sequences can also be used to determine how closely related organisms are Page 4 of 6 © 2015 − 2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources Three Domain System Due to evidence available from chemical analysis, there is now a ‘three-domain system’

FAQs

How is a species defined in GCSE Biology classification notes?

A species is defined as a group of organisms that can reproduce to produce fertile offspring. This ability to produce fertile offspring is the basis for grouping organisms.

What is the Linnaean binomial system and what do genus and species represent?

In the binomial system, each organism’s scientific name has two parts: the genus (capital letter) and the species (lowercase letter). Binomial names are written in italics to indicate Latin.

How does DNA sequencing change organism classification?

DNA sequencing enables classification based on genetic similarity. More similar DNA base sequences indicate closer relatedness and a more recent common ancestor.

Sep 5, 2026

Upload by Levi