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Practise 34 exam-style questions on Classification of living organisms for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
The scientific name of the Norway spruce is Picea abies. Identify the genus and the species (specific epithet).
Genus = Picea; Species (specific epithet) = abies
In binomial nomenclature the first word is the genus (capitalized) and the second is the specific epithet (lowercase). Together they identify the species.
Genus: Picea
Species/specific epithet: abies
What is meant by homology in comparative anatomy and how does it differ from analogy?
Homology: similarity due to shared ancestry (same structure modified); Analogy: similarity due to convergent evolution/ similar function but different ancestry.
Homologous structures (e.g. forelimbs of vertebrates) reflect inheritance from a common ancestor; analogous structures (e.g. wings of insects and birds) evolved independently for similar functions.
Homology = similarity due to common ancestry (same structure inherited)
Analogy = similarity due to convergent evolution (similar function but different origin)
Describe two pieces of evidence that led Carl Woese to propose the domain Archaea as separate from Bacteria.
Differences in ribosomal RNA sequences and differences in membrane lipid chemistry / cell wall composition; some Archaea live in extreme environments.
Woese's comparisons of rRNA showed that organisms previously grouped as bacteria actually formed two very different molecular lineages. Biochemical differences in membrane lipids and unique physiology (e.g. extremophiles) supported separating Archaea as its own domain.
Ribosomal RNA sequence differences (Woese used rRNA comparisons)
Different membrane lipid structure / different biochemistry (phospholipids) / cell wall differences
Ecological/physiological differences (many Archaea live in extremes) supporting distinct lineage
Interpret the following simple cladogram clue: species X and Y share a node not shared with species Z. What does this say about their relationships and common ancestors?
X and Y are more closely related to each other than either is to Z; X and Y share a more recent common ancestor; Z diverged earlier from the lineage.
In a cladogram, nodes indicate common ancestors; species that share a node are closer relatives and diverged more recently than species branching off earlier.
X and Y are more closely related to each other than to Z
X and Y share a more recent common ancestor (represented by the node)
Z split off earlier (has a more distant common ancestor with X and Y)
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