Evolution is cumulative change in heritable characteristics of a population. Three words do the work: heritable, population, and generations. A muscle gained during one organism’s life is acquired, not inherited in the Darwinian sense, so it is not evolution by itself. Evolution is measured when inherited traits become more or less common across generations.

Evolution is cumulative change in heritable characteristics of a population.

Evolution happens across generations, not inside one individual lifetime.

Acquired characteristics are not inherited in the Darwinian sense.

The exam trap is confusing individual change with population-level heritable change.

Which sentence defines evolution correctly?

Choose

Molecular evidence gives two levels of support for evolution. Shared universals such as DNA, the genetic code, ATP use, and core metabolism support common ancestry. Sequence differences in DNA, RNA, and proteins then help compare relatedness and divergence: fewer differences usually suggest a more recent common ancestor, while more differences suggest longer separation.

Universal DNA, genetic code, ATP use, and core metabolism support common ancestry.

DNA, RNA, and protein sequence differences indicate relatedness and divergence.

Fewer sequence differences usually suggest closer relatedness.

Molecular evidence can test relationships beyond appearance.

Use molecular universals for common ancestry and sequence differences for divergence.

Match each molecular clue to what it supports.

Match

Reasons

0/4

Match each molecular clue to what it supports.

Choose

Selective breeding is useful because it makes selection visible. Humans choose which organisms reproduce, so heritable traits can change rapidly over generations. Pigeons, domesticated animals, Brassica crops, wheat, and maize show that strong selection can shift inherited traits away from the wild form. This supports Darwin’s idea that natural selection can also change populations, only with environmental selection instead of human choice.

Selective breeding shows traits can change rapidly under selection.

Artificial selection acts on heritable variation in a population.

Examples include pigeons, domesticated animals, Brassica crops, wheat, and maize.

Selective breeding supports the logic of natural selection by showing selection can shift heritable traits.

Selection can push visible trait change quickly when breeders control reproduction.

Match each example to the selective-breeding idea it shows.

Match

Reasons

0/4

Match each example to the selective-breeding idea it shows.

Choose

Homologous and analogous structures answer different questions. Homologous structures share ancestry even if their functions differ; vertebrate pentadactyl limbs support divergent evolution and adaptive radiation. Analogous structures have similar functions but different evolutionary origins; bat and insect wings are similar because similar selection pressures produced convergence.

Homologous structures share ancestry even when functions differ.

Pentadactyl limbs support divergent evolution and adaptive radiation.

Analogous structures have similar functions but different evolutionary origins.

Convergent evolution occurs when similar selection pressures produce similar features.

Homology asks whether the structure shares ancestry; analogy asks whether similar function evolved independently.

Sort each example into homologous or analogous/convergent evidence.

Sort

Unsorted

5

homologous evidence

0

analogous/convergent evidence

0

Sort each example into homologous or analogous/convergent evidence.

Choose

vertebrate pentadactyl limb

bird, bat, and human forelimb bones

bat wing and insect wing as flying structures

same function but different evolutionary origin

common ancestral limb pattern

Speciation means one pre-existing species splits into new species. The key switch is reduced gene flow. Once gene pools are isolated, selection, mutation, and genetic drift can make them diverge. Geographic separation and different selection pressures often start the process; chimpanzees and bonobos illustrate river-linked isolation and later divergence.

Speciation forms new species by splitting a pre-existing species.

Reproductive isolation reduces gene flow so populations can diverge.

Isolated gene pools diverge through selection, mutation, and genetic drift.

Geographic separation plus different selection pressures can drive speciation.

Chimpanzees and bonobos illustrate river-linked isolation and divergence.

Speciation begins when gene flow drops and separated gene pools start changing independently.

Put the speciation mechanism in order.

Order

1

new species form

2

separate gene pools form

3

one pre-existing species

4

reproductive differences accumulate

5

selection, mutation, and drift act differently

6

reproductive or geographic isolation reduces gene flow

Put the speciation mechanism in order.

Choose

one pre-existing species

reproductive or geographic isolation reduces gene flow

separate gene pools form

selection, mutation, and drift act differently

reproductive differences accumulate

new species form

The core A4.1 answer moves from evidence to mechanism. Define evolution as heritable population change across generations. Use molecular universals and sequence differences, selective breeding, homology, and convergence as evidence for common ancestry and divergence. Then explain speciation as reduced gene flow followed by divergence of isolated gene pools through selection, mutation, and drift.

Evolution is cumulative change in heritable characteristics of a population.

Molecular evidence supports common ancestry and divergence.

Selective breeding shows heritable traits can change rapidly under selection.

Homology supports common ancestry; analogy/convergence shows similar selection pressures can mislead.

Speciation needs reduced gene flow and divergence of isolated gene pools.

Match each core idea to its exam role.

Match

Use this for combined questions on evidence for evolution or how speciation begins.

Define evolution as cumulative change in heritable characteristics of a population.

Use molecular universals and sequence differences as evidence for common ancestry and divergence.

Use selective breeding as evidence that selection can change heritable traits across generations.

Distinguish homologous structures from analogous/convergent structures.

Explain speciation by reduced gene flow, reproductive isolation, and divergence through selection, mutation, and drift.

Use this for combined questions on evidence for evolution or how speciation begins.

Evolution is cumulative change in heritable characteristics of a population across generations. Evidence includes shared DNA, genetic code, ATP use and core metabolism, plus DNA/RNA/protein sequence differences that indicate relatedness. Selective breeding shows that heritable traits can change rapidly under selection. Homologous structures such as pentadactyl limbs support common ancestry, while analogous structures such as bat and insect wings show convergence. Speciation begins when reproductive isolation reduces gene flow, allowing separated gene pools to diverge through selection, mutation and genetic drift.

Listing examples without explaining whether they support common ancestry, convergence, or speciation.

IB Biology SL A4.1 Evolution and speciation Notes

Define Evolution As Population Change

Use Molecular Evidence For Common Ancestry

Use Selective Breeding As Visible Evidence

Separate Homology From Convergence

Trace How Speciation Begins

SL Transfer: Evidence To Speciation