HL 2 Biology

D.2c: Sympatric Speciation


  • can lead to sympatric speciation
  • become reproductively isolated from original population

Polyploid organism: one that has more than two sets of homologous chromosomes

e.g. polyploidy plants – can self-pollinate or mate with other polyploidy plants

There are polyploids that result from:

  • hybridization events between different species
  • whose chromosomes originate from the same ancestral species – autopolyploidy
    • chromosomes duplicate in prep for meiosis but then meiosis doesn’t occur
    • result: diploid gamete that when fused with a haploid gamete = produces a fertile offspring


Lacewing Songs (p.29)

1) Although both C. lucasina and C. mediterranea range from 4 to -4, the C. lucasina has a more steady repetitive rhythm throughout the song. Yet in contrast, the C. mediterranea has an inconsistent oscillations in which the range starts small and increases and decreases again. The C. mediterranea has a greater variation in the ranges throughout the song compared to that of C. lucasina. 

2) Differences in mating songs might lead to speciations because they would attract different groups of female lacewings in respect to the different songs. Since the songs differ, each male may get the interest from different females. This will result with the two different groups of lacewings to be reproductively isolated as the varied gene pools form.

3) (a) Allopatric speciation is when the isolation occurs because of geographic speciation of species. Thus, differences in the song could have developed by allopatric speciation because different songs may have been more advantages in the different environment the males lived in, to attract the females. The varied ranges in of oscillations may have been one factor which altered the effectiveness of attracting females and lead to speciation between the two groups.

(b) Sympatric speciation is when isolation occurs within the same habitat but have different behavioral patterns and live in different niches within the habitat. The differences in the song could have developed by sympatric speciation as the different niches may have developed their own unique version of the song resulting with the attraction of different female groups. The groups of these birds may have limited their interbreeding population as the songs became more distinct and unique, leading to speciation.

One thought on “D.2c: Sympatric Speciation

  1. Blog DP

    Grade 6 A consistent and thorough understanding of the required knowledge and skills, and the ability to apply them in a wide variety of situations. Consistent evidence of analysis, synthesis and evaluation is shown where appropriate. The student generally demonstrates originality and insight.

    Data-based questions page 313
    • Duration of song: a > b
    • Duration of notes: a > b
    • Variation in frequency: b > a
    • Number of notes: b > a
    • Maximum frequency: a = b

    • biological species concept: species = group of organisms
    – capable of interbreeding and producing fertile offspring
    – isolated from other group
    • mating calls
    – act as reproductive isolating mechanisms
    – are pre-zygotic
    – are species speccific

    • geographical isolation
    • divergence due to unique selective pressures
    • reproductive isolation

    • ecological isolation
    • divergence due to unique selective pressures
    • reproductive isolation

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