AHL Content Statements

• A4.1.8

  Differences and similarities between sympatric and allopatric speciation
  

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  Students should understand that reproductive isolation can be geographic, behavioural or temporal.
  

• A4.1.9

  Adaptive radiation as a source of biodiversity
  

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  Adaptive radiation allows closely related species to coexist without competing, thereby increasing biodiversity in ecosystems where there are vacant niches.
  

• A4.1.10

  Barriers to hybridization and sterility of interspecific hybrids as mechanisms for of preventing the mixing of alleles between species
  

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  Courtship behaviour often prevents hybridization in animal species. A mule is an example of a sterile hybrid.
  

• A4.1.11

  Abrupt speciation in plants by hybridization and polyploidy

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  Use knotweed or smartweed (genus Persicaria) as an example because it contains many species that have been formed by these processes.
  

• A3.1.12

  Difficulties applying the biological species concept to asexually reproducing species and to bacteria that have horizontal gene transfer

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  The biological species concept does not work well with groups of organisms that do not breed sexually or where genes can be transferred from one species to another.
  

• A3.1.13

  Chromosome number as a shared trait within a species

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  Cross-breeding between closely related species is unlikely to produce fertile offspring if parent chromosome numbers are different.
  

• A3.1.14

  Engagement with local plant or animal species to develop a dichotomous key

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  AOS: Students should engage with local plant or animal species to develop a dichotomous key.
  

• A3.1.15

  Identification of species from environmental DNA in a habitat using barcodes

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  Using barcodes and environmental DNA allows the biodiversity of habitats to be investigated rapidly.