Written for this site from the class slides, with textbook page references for each statement. The chapter is on pages 151–155 of the course textbook. Image credits are on slide 12.
In both, gene pools are isolated and then diverge. In allopatric speciation the populations are separated geographically; in sympatric speciation they share an area but are isolated by behaviour or timing.
One ancestral species diversifies into many that fill different niches, as in Galápagos finches or bromeliads. Because they use different resources, close relatives can coexist without competing, which raises biodiversity.
Species-specific courtship usually stops animals mating with other species. If hybrids do form, they are often sterile, as mules are, so alleles do not pass between species.
Two species hybridize; the sterile hybrid doubles its chromosomes and becomes fertile. The new polyploid cannot breed successfully with its parents, so it is a new species at once. Many species of Persicaria (knotweeds and smartweeds) arose this way.
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Print this guide and complete it as you work through the slides and videos. It asks for your own explanations, so close the notes while you try each section.
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A printable worksheet covering all four statements, from quick recall to data questions and a longer answer. It has 20 marks and takes about 20 minutes, or you can do one section at a time.
Your teacher has the mark scheme.
You will need: Two cups, coloured beads as alleles, dice, a different selection rule for each cup
Safety: Keep beads off the floor to avoid slips.
Carry this out with your teacher's supervision and follow your school's lab rules.
The Grants observed a new finch lineage arise after a hybridization event on Daphne Major, within a few generations.
Most speciation happened long before anyone could watch. Consider how evolutionary biology's methods compare with those of history.
Summarised in our own words. Use each code to find the exact wording in your textbook or the IB subject guide.
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