Zadanie 9, Paper 2, maj 2025, TZ2, Biologia IB HL
Wzorowane na: Biology HL Paper 2, May 2025, TZ2, pytanie 9. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Polecenie
Biologists use inherited similarities and differences to investigate population change and relationships.
(a) Describe how homologous structures provide evidence for evolution.
(b) Outline the assumptions and use of Hardy–Weinberg calculations in a population with two alleles at one locus.
(c) Explain how evolutionary relationships and cladograms support biological classification.
One additional mark is available for clear, concise communication across the whole response.
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Odpowiedź z klucza
(a) Homologous structures share an underlying anatomical pattern despite sometimes performing different functions. ✔
Divergent selection or adaptive radiation can modify this inherited pattern. ✔
Their shared structure supports descent from a common ancestor. ✔
Homologies can be traced in fossil remains. ✔
Comparisons of living structures, vestigial organs, embryos or homologous molecular sequences provide additional evidence. ✔
For example, the forelimbs of a bat and a horse share the pentadactyl ancestral pattern. ✔
(b) The model assumes no mutation. ✔
Mating is random at the locus. ✔
There is no migration or gene flow. ✔
The population is sufficiently large for negligible genetic drift. ✔
There is no selection favouring one genotype. ✔
The symbols p and q denote allele frequencies. ✔
The allele frequencies satisfy p + q = 1. ✔
At equilibrium p² + 2pq + q² = 1. ✔
The homozygote frequencies are p² and q², and heterozygote frequency is 2pq; these relations allow genotype and allele frequencies to be related. ✔
(c) Classification organizes great species diversity and aids identification and study. ✔
A phylogenetic classification groups organisms according to shared ancestry. ✔
Shared ancestry allows predictions about other characteristics of group members. ✔
Morphology, development and molecular sequence data can provide evidence of relationships. ✔
Greater similarity of homologous sequences or structures generally supports closer relatedness. ✔
Mutations produce differences in homologous sequences over time. ✔
A cladogram is a branching representation of descent from ancestral lineages. ✔
Its topology is inferred from phylogenetic evidence, for example aligned homologous sequences. ✔
A clade includes one common ancestor and all its descendants. ✔
The root represents the ancestral lineage shared by all included taxa. ✔
An internal node represents a common ancestor and lineage divergence. ✔
Terminal branches represent the sampled species or other groups. ✔
Communication: explanations are clear, focused and concise across the whole response. ✔
Schemat punktowania
(a) Any 4 points, max 4. (b) Any 3 points, at most 2 for assumptions and 2 for use, max 3. (c) Any 8 distinct points, max 8; clearly annotated diagrams may earn relevant points. Add 1 holistic clarity mark, maximum 16. In (b), homozygote frequencies p² and q² OR heterozygote frequency 2pq suffices for the genotype-frequency point. In (c), identifying the root as the base of the tree OR its common ancestral lineage suffices.