Phylogenetic Classification
Laura Armstrong
Teacher

Contents
Recall Questions
This topic requires prior knowledge of classification from GCSE. You can test your knowledge on this below.
What is the binomial baming system and why is it used?
The Binomial Naming System is a universal system that gives each species a two-part Latin name (Genus followed by species). It avoids confusion caused by common names in different languages and ensures consistency in scientific communication.
What are the five main kingdoms of classification in biology?
Prokaryotae (bacteria), Protoctista, Fungi, Plantae, and Animalia.
What is the biological definition of the term "species"?
Organisms that can interbreed to produce fertile offspring.
Topic Explainer Video
Check out this @LauraDoesBiology video that explains phylogenetic classification or read the full notes below. Once you've gone through the whole note, try out the practice questions!
What is Phylogenetic Classification?
Definition:
- A system of classification based on evolutionary history and common ancestry, grouping organisms according to how closely they are related.
Comparison to Traditional Classification:
- Traditional classification uses observable features, whereas phylogenetics uses genetic and molecular data.
- Traditional classification looks at analogous structures - features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestor.
- Phylogenetic classification looks at homologous structures - features of different species that derive from a common ancestor.
Hierarchy in Classification
- Hierarchical System: Organisms are classified into larger groups and then placed within smaller groups, with no overlap between groups.
Taxonomic Ranks (Largest to Smallest):
- Domain.
- Kingdom.
- Phylum.
- Class.
- Order.
- Family.
- Genus.
- Species.
Mnemonic for Order: "Dear King Philip Came Over For Good Soup."
Phylogeny and Evolutionary Trees
- Phylogeny: The study of evolutionary relationships and shared common ancestors.
- Phylogenetic Trees:
- Show common ancestors and evolutionary history.
- Branching points represent divergence from a common ancestor.
- Closer branches indicate closer evolutionary relationships as they show organisms shared a more recent common ancestor.
The Binomial Naming System
- Developed by Carl Linnaeus.
- Format: Genus species (e.g., Homo sapiens).
- Rules:
- Genus name is capitalised, species name is lowercase.
- Names are written in italics (or underlined when handwritten).
Using The Scientific Binomial is Advantageous:
- It avoids confusion caused by common names in different languages and ensures consistency in scientific communication.
- It also allows us to consider evolutionary relationships between species. For example, if the species share the same genus, they are more closely related and share a more recent common ancestor.
Key Terms
- Phylogenetics: The study of evolutionary relationships.
- Taxonomy: The science of classification.
- Binomial Naming System: A universal two-part naming system for species.
- Hierarchy: A system of ranking where smaller groups are placed within larger groups with no overlap.
- Molecular Phylogenetics: Using DNA and protein sequences to determine evolutionary relationships.
- Species: Organisms that can interbreed to produce fertile offspring.
Exam Tips
Make sure you understand the difference between classification and phylogeny! Classification groups organisms, whereas phylogeny shows their evolutionary relationships. Phylogenetic trees often appear in exam questions, so practice interpreting them.
The cheetah, Acinonyx jubatus, and other cat species belong to the family Felidae.
1. Complete the table to show the classification of the cheetah. (2 marks)
Kingdom | Animalia |
Chordata | |
Mammalia | |
Carnivora | |
Family | Felidae |
Genus | |
2. This system of classification is described as hierarchical. Explain what is meant by a hierarchical classification. (2 marks)
1. Down left hand column: Phylum, Class, Order, Species.
Down right hand column: Acinonyx, Jubatus.
2. Larger groups containing smaller groups with no overlap.
Practice Question 1
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!
Practice Question 2
If you want to try out another one, check this video out and see how you do!