Zadanie 7, Paper 2, maj 2024, TZ1, Biologia IB HL
Wzorowane na: Biology HL Paper 2, May 2024, TZ1, pytanie 7. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Polecenie
(a) Outline what makes DNA replication semi-conservative.
(b) Describe how sexual reproduction generates genetic variation.
(c) Explain how isolated populations can become separate species.
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Odpowiedź z klucza
(a)
New DNA strands are produced using existing DNA. ✔
Free nucleotides are added along exposed template bases. ✔
Complementary pairing determines which nucleotide is incorporated. ✔
Each parental strand acts as a template. ✔
Each resulting double helix contains one parental strand and one newly synthesized strand. ✔
(b)
Meiosis produces haploid cells/gametes OR segregates alleles OR breaks up parental allele combinations. ✔
Crossing over OR chiasma formation occurs. ✔
DNA or alleles are exchanged between homologous chromosomes OR crossing over generates recombinant allele combinations. ✔
Homologous pairs orient randomly at meiosis I OR chromosomes assort independently. ✔
This produces different combinations of maternal and paternal chromosomes. ✔
Fertilization brings together alleles from two parents. ✔
Random combinations of gametes or mates add further variation. ✔
(c)
Speciation forms new species from an ancestral population. ✔
Reproductive isolation prevents interbreeding. ✔
Gene flow is restricted, separating gene pools. ✔
Different breeding times can cause temporal isolation. ✔
Different mating behaviour can cause behavioural isolation. ✔
A physical barrier can produce geographical isolation. ✔
Mutations OR genetic drift may differ between populations. ✔
Different environments impose different selective pressures. ✔
Allele frequencies diverge. ✔
The populations show evolutionary divergence OR evolve different adaptations. ✔
Accumulated differences can prevent production of fertile offspring, even after contact resumes; alternatively, polyploidy can cause immediate reproductive isolation. ✔
Quality of communication: clear on first reading, concise and without unnecessary repetition or irrelevant material. ✔
Schemat punktowania
Part (a): any 3 points, maximum 3. Part (b): any 5 points, maximum 5. Part (c): any 7 points, maximum 7. Award 1 independent communication mark across the complete answer. Maximum 16. Accept scientifically equivalent wording and relevant annotated diagrams.