Gene pools and speciation 10.3 HL

The concept of gene pools is important to the understanding of natural selection. There are three types of selection pressure covered in this topic, stabilising, directional and disruptive. In situations where there is reproductive isolation between two populations of a species speciation can occur. This topic explores this mechanism of evolution and the concepts of punctuated equilibrium and polyploidy

Key concepts

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Essentials

These slides summarise the essential understanding and skills in this topic. 
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Summary

Summary list for 10.3 Gene pools and speciation

Gene pools

  • A gene pool consists of all the genes and their different alleles, present in an interbreeding population.
  • Evolution requires that allele frequencies change with time in populations.
  • Punctuated equilibrium implies long periods without appreciable change and short periods of rapid evolution.

Speciation

  • Reproductive isolation of populations can be temporal, behavioural or geographic.
  • Speciation due to divergence of isolated populations can be gradual.
  • Speciation can occur abruptly.

Student skills and applications

  • Application: Identifying examples of directional, stabilising and disruptive selection.
  • Application: Speciation in the genus Allium by polyploidy.
  • Skill: Comparison of allele frequencies of geographically isolated populations.

Mindmaps

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Exam style questions

Exam style question about speciation

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Describe how geographical isolation and different selective pressures can lead to speciation [3]

 

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Extra exam question on polyploidy and abrupt speciation.    Click to open.

Linking genetic chnages to evolution is an important concept in this topic.

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Explain how polyploidy can cause abrupt speciation. (3 marks).





Hint: Make sure that your answer links polyploidy to speciation.
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Extra exam question on the gradual change of allele frequencies as a species evolves.    Click to open.

The understanding that evolution is a change in allele frequencies in gene pools over time is an important concept in this topic.

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Explain how environmental change can lead to changes in allele frequency in a single population. (4 marks).





Hint:

Explain requires the reasons for change in this question. The question is not about speciation but the evolution of a single species. It is necessary to link the two concepts in the question - environmental change and allele frequency changes.

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Test yourself

Multiple choice questions

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Drag and drop activities

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Isolation of two populations is a mechanism of speciation.

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Behavioural Natural mechanisms seasons Temporal interbreeding physical barrier Breeding selection pressures characteristics

Isolation prevents two groups of a species from . If each of the groups is subjected to differing , their genomes will gradually evolve in different ways due to different genes having favourable in the different environments.

Three forms of isolating are:

  1. Geographical isolation where a such as a river separates the two populations.
  2. isolation where the activity times or breeding separate the two populations.
  3. isolation where members of each group choose to breed only with members of that group

Isolation prevents interbreeding and can lead to speciation over time.


Just for fun

Just for fun

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