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IB Biology A3.2: Clas. & Clad. — Practice Questions & Answers
IB Biology A3.2 study notes: the taxonomic hierarchy, natural versus artificial classification, clades, cladograms and reclassification using molecular evidence.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
Why is classification of organisms needed?
Immense diversity of species
Lack of evolutionary relationships
To classify all possible genetic variations within a population
To create a visual representation of all living things
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Why Classification is needed to organise and make sense of the immense diversity of species on Earth.
2
Multiple choice
What is a limitation of the traditional hierarchy of taxa?
Does not always correspond to evolutionary divergence
Too many levels
Too few levels
Lack of binomial nomenclature
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Why The traditional hierarchy of taxa does not always reflect the true pattern of evolutionary divergence.
3
Multiple choice
What is an advantage of classification corresponding to evolutionary relationships?
Predictable characteristics within a clade
Simpler hierarchy
It allows for the easy identification of organisms based solely on physical appearance
It ensures that all organisms are grouped according to their ecological roles
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Why Classification based on evolutionary relationships lets us predict shared characteristics among members of a clade.
4
Multiple choice
What is a clade?
Group of organisms with common ancestry and shared characteristics
Group of organisms with similar morphology
Group of organisms with similar habitats
Group of organisms with similar behaviors
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Why A clade is a group of organisms comprising a common ancestor and all of its descendants, sharing derived characteristics.
5
Multiple choice
What is the most objective evidence for placing organisms in the same clade?
Base sequences of genes or amino acid sequences of proteins
Morphological traits
Behavioral patterns
Geographical location
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Why Base sequences of genes and amino acid sequences of proteins give quantifiable, objective molecular evidence for grouping organisms into clades.
6
Multiple choice
What is used to estimate when clades diverged from a common ancestor?
Molecular clock
Morphological clock
Behavioral clock
Geographical clock
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Why A molecular clock uses the roughly constant accumulation of mutations over time to estimate when clades diverged.
7
Multiple choice
What affects mutation rates in the molecular clock?
Generation time, population size, selective pressure
Habitat size, food availability, temperature
Light intensity, water availability, pH
Wind speed, humidity, altitude
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Why Mutation rates are influenced by generation time, population size and selective pressure, affecting molecular clock accuracy.
8
Multiple choice
What is used to construct cladograms?
Base sequences of genes or amino acid sequences of proteins
Morphological traits
Behavioral patterns
Geographical location
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Why Cladograms are built from base sequences of genes or amino acid sequences of proteins, which reveal shared ancestry.
9
Multiple choice
What is used to select the most probable cladogram?
Parsimony analysis
Morphological analysis
Behavioral analysis
Geographical analysis
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Why Parsimony analysis selects the cladogram requiring the fewest evolutionary changes as the most probable.
10
Multiple choice
What does a node in a cladogram represent?
Hypothetical common ancestor
Extinct species
Living species
Hybrid species
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Why A node marks a hypothetical common ancestor from which two or more lineages diverged.
Key terms in Clas. & Clad.
Taxonomy: The science of identifying, naming and classifying organisms into a hierarchy of groups.
Binomial system: The two-part naming system (genus then species epithet) used to give each species a unique Latin name, such as <em>Homo sapiens</em>.
Natural classification: Grouping organisms according to shared evolutionary ancestry, giving the system predictive power.
Artificial classification: Grouping organisms by convenient observable features that need not reflect ancestry.
Clade: A group consisting of a common ancestor and all of its descendants.
Cladogram: A branching diagram showing hypothesised evolutionary relationships, with nodes representing common ancestors.
Homologous structures: Features shared because of common ancestry, even if their current function differs.
Molecular clock: The idea that mutations accumulate at a roughly constant rate, so sequence differences estimate the time since divergence.
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