• Classification organizes biodiversity into groups with shared characteristics
• Universal taxonomy supports communication, comparison, and further study
• Classification helps reveal functional, structural, and evolutionary relationships
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Mastery
0
Attempts
0
Mistakes
Start with the concept explanation, then practise to create mastery evidence.
2
Learning objective
A3.2.2 (HL)—Difficulties with traditional hierarchy
New
• Traditional hierarchy uses kingdom, phylum, class, order, family, genus, and species
• Fixed ranks can be arbitrary and may not match evolutionary divergence
• Morphological similarity can reflect convergence rather than common ancestry
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Mastery
0
Attempts
0
Mistakes
Start with the concept explanation, then practise to create mastery evidence.
3
Learning objective
A3.2.3 (HL)—Advantages of evolutionary classification
New
• Evolutionary classification aims to match phylogeny
• Natural groups are monophyletic and include an ancestor plus all descendants
• DNA and protein evidence can correct misleading morphology
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Mastery
0
Attempts
0
Mistakes
Start with the concept explanation, then practise to create mastery evidence.
4
Learning objective
A3.2.4 (HL)—Clades
New
• A clade is a group evolved from a common ancestor
• Clades are identified using shared derived characteristics, or synapomorphies
• Evidence may be anatomical, behavioural, genetic, or protein sequence data
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Mastery
0
Attempts
0
Mistakes
Start with the concept explanation, then practise to create mastery evidence.
5
Learning objective
A3.2.5 (HL)—Molecular clock
New
• Sequence differences accumulate after clades diverge
• Molecular clocks estimate divergence time from DNA or amino acid differences
• Rates must be calibrated and can vary between genes or lineages
0%
Mastery
0
Attempts
0
Mistakes
Start with the concept explanation, then practise to create mastery evidence.
6
Learning objective
A3.2.6 (HL)—Constructing cladograms
New
• Cladograms can be built by aligning DNA, RNA, or protein sequences
• Computer analysis infers trees that best explain sequence similarities
• Parsimony favours the tree requiring the fewest evolutionary changes
0%
Mastery
0
Attempts
0
Mistakes
Start with the concept explanation, then practise to create mastery evidence.
7
Learning objective
A3.2.7 (HL)—Analysing cladograms
New
• Nodes represent common ancestors or speciation events
• Branch points show order of divergence, not simply end-position similarity
• Roots, terminal branches, ingroups, outgroups, and sister groups support interpretation
0%
Mastery
0
Attempts
0
Mistakes
Start with the concept explanation, then practise to create mastery evidence.
8
Learning objective
A3.2.8 (HL)—Testing classification correspondence
New
• Cladistics tests whether traditional taxa match evolutionary relationships
• Figwort family reclassification used conserved chloroplast gene sequences
• Some morphological similarities were falsified as convergence
0%
Mastery
0
Attempts
0
Mistakes
Start with the concept explanation, then practise to create mastery evidence.
9
Learning objective
A3.2.9 (HL)—Three domains classification
New
• rRNA sequence evidence separated prokaryotes into eubacteria and archaea
• Three domains are Archaea, Eubacteria, and Eukarya
• Domains differ in rRNA, chromosomes, histones, introns, cell walls, and membrane lipids
0%
Mastery
0
Attempts
0
Mistakes
Start with the concept explanation, then practise to create mastery evidence.