Heredity and evolution — Intermediate

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Level 2: Intermediate

Explain, apply, analyse, sequence — connect ideas, read patterns, use rules in new contexts (bridge to Year 11).

1. Why does meiosis (rather than mitosis alone) increase genetic variation in sexually reproducing species?

   A)Because DNA replication is error-free and crossing over makes homologues identicalB)Because crossing over and independent assortment shuffle alleles, and halving ploidy lets fertilisation merge two genomesC)Because crossing over removes variation by forcing sister chromatids to matchD)Because meiosis runs in somatic cells whenever routine DNA damage is repaired

2. Two heterozygotes Bb × Bb (complete dominance, B dominant). What fraction of offspring are expected to be homozygous dominant?

   A)One quarter, matching the BB cells in the Punnett squareB)One half, as for any single dominant allele countC)Three quarters, counting every offspring with a dominant phenotypeD)One eighth, as if three independent genes were involved

3. A student says: organisms evolve because they try hard to survive. Which response is most accurate?

   A)Partly true, because effort steers which mutations appear in sperm and eggsB)Misleading, because evolution in nature stopped once humans appearedC)Natural selection sorts existing variation; individuals do not choose beneficial mutations that wayD)True, because environments make whole populations adapt even without variation

4. Comparative DNA sequences between species support evolution when:

   A)Housekeeping genes are byte-for-byte identical in every species testedB)Closer relatives share higher sequence similarity than deeper splits in timeC)Equal mutation rates in every lineage make similarity mean convergence onlyD)Only non-coding DNA can be compared between species

5. In a population of bacteria exposed to antibiotics, resistant forms may become more common mainly because:

   A)Low doses reliably strip resistance genes from every cell at onceB)Resistance appears only when the drug arrives, with no genetic basisC)All cells are genetically identical, so survival is unrelated to genotypeD)Heritable differences exist, and resistant genotypes reproduce more under that selection

6. Fossil sequences in rock layers can support evolution by showing:

   A)Deeper strata can hold simpler or distinct forms compared with younger bedsB)Unchanging index fossils prove species never evolve at allC)All layers in a column formed in one catastrophic day onlyD)Body fossils occur only in igneous rock with no sedimentary record

7. Which pair best contrasts mitosis and meiosis?

   A)Mitosis yields four haploid gametes after two divisionsB)Mitosis halves chromosomes while meiosis doubles them in daughter cellsC)Mitosis keeps the diploid complement in somatic divisions; meiosis halves chromosomes to form gametesD)Both finish with four genetically identical diploid cells in animals

8. DNA replication before mitosis ensures each daughter cell receives:

   A)Half the parent DNA with no prior duplication stepB)A full chromosome complement matching the parent when chromatids separate correctlyC)Only messenger RNA copies instead of chromosomal DNAD)Random single strands unrelated to the parent templates

9. Mutation can be important in evolution because it:

   A)Guarantees adaptive improvement within a single generationB)Removes all genetic variation from a population immediatelyC)Only alters body cells that offspring then inherit unchangedD)Supplies new alleles that selection, drift, and gene flow can then reshape over time

10. In complete dominance, a heterozygote Aa for a trait typically shows:

    A)The dominant phenotype when only one dominant allele is presentB)A perfect blend always midway between both homozygotesC)The recessive phenotype despite carrying a dominant alleleD)No phenotype at all because the alleles cancel out

11. Speciation often involves:

    A)Instant identical copies of one parent species spreading everywhereB)Complete loss of all genetic variation before populations split apartC)Gradual genetic and ecological divergence plus barriers that limit gene flowD)Purely behavioural shifts with no underlying genetic change at all

12. In meiosis, independent assortment of homologous pairs contributes to variation because:

    A)It copies DNA without errors in every divisionB)Different combinations of maternal and paternal chromosomes enter gametesC)It doubles chromosome number in the products of meiosisD)It occurs only in body cells and never in germ-line tissue

13. A monohybrid cross Aa × aa with complete dominance: what fraction of offspring are expected to show the recessive phenotype?

    A)None, because the dominant parent always masks recessive expressionB)One quarter, as in an Aa × Aa crossC)One half, because the Aa parent passes a half the timeD)All offspring, because aa always appears in this cross

14. Why is inbreeding often associated with higher expression of recessive disorders?

    A)It raises homozygosity, pairing recessive alleles more oftenB)It removes every recessive allele from the populationC)It rewrites DNA sequence in every generation predictablyD)Recessive alleles exist only in outbred populations, never inbred ones

15. Vestigial structures are interpreted in evolution partly as:

    A)Proof that hereditary molecules are absent in those lineagesB)Structures that always keep their original selective function unchangedC)Only convergent traits from unrelated evolutionary lineagesD)Reduced or altered remnants whose form fits ancestry with modification

16. Antibiotic misuse can speed resistance spread because it:

    A)Removes all mutations from the bacterial populationB)Increases selection pressure on heritable variation already presentC)Stops natural selection from acting in hospitals or farmsD)Prevents horizontal gene transfer between bacterial cells entirely

17. Gene flow between populations tends to:

    A)Cause speciation instantly whenever migrants arriveB)Reduce genetic differences between populations by mixing allelesC)Remove all alleles from both populations in one eventD)Act only on somatic cells rather than breeding populations

18. Sexual reproduction can speed adaptation in changing environments partly because it:

    A)Recombines existing alleles into new genotype combinationsB)Removes all variation at fertilisation each generationC)Copies parents exactly with no shuffling of allelesD)Eliminates natural selection by keeping genotypes fixed

19. Independent assortment of two genes is most straightforward in a dihybrid cross when:

    A)The genes sit on different chromosomes so they segregate separatelyB)Dominance is incomplete, which changes how phenotypes lookC)The cross is designed as a test cross with a homozygous recessiveD)The genes are tightly linked on one chromosome, which can break simple ratio expectations

20. Nondisjunction can produce gametes with the wrong chromosome count because:

    A)Homologues or sister chromatids fail to separate properly in meiosisB)Mitosis always triples DNA before cytokinesisC)Crossing over deletes whole chromosomes from the nucleusD)Fertilisation never joins gametes in living species

21. Homology versus analogy: wings of insects and birds are often cited as:

    A)Always homologous because both are used for flightB)Identical in DNA sequence between phylaC)Only analogous if the wings are exactly the same sizeD)Analogous, with similar function but different evolutionary origins

22. Many offspring from Aa × Aa are expected to show a 3 : 1 phenotype ratio, yet one family’s first four children might not match it because:

    A)Ratios apply only to plants and never to animalsB)Small samples can depart from expectation by chance aloneC)Dominant alleles always appear in exactly three of every four birthsD)Meiosis guarantees each family matches Punnett ratios exactly

23. During industrial melanism, darker moths became more common in soot-darkened habitats mainly because:

    A)Individual moths chose to grow darker pigment to match treesB)Pollution directly edited moth DNA in one generation for all survivorsC)Heritable colour variants differed in survival where camouflage matteredD)Light moths stopped breeding while dark moths learned to hide better

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