NATURAL SELECTION AND SPECIATION
The anole lizard of the Caribbean Islands represents a group of about 150 closely
related species, which evolved within the past 50 million years from a single
species. Use this example to describe how natural selection led to the process of
speciation that gave rise to the 150 different species of lizards.
Natural selection and speciation
• The original species of anole lizards was separated
• Into different populations
• by a geographical barrier
• which is the sea
• There was no gene flow
• between the separated populations
• Each population was exposed to different environmental conditions
• on each island
• Because there is variation
• amongst the lizards
• Natural selection occurred independently
• in each population
• Some had favourable characteristics
• to survive on a specific island
• while others did not
• The ones that did not have the favourable characteristics died
• The ones with the favourable characteristic survived
• and reproduced to pass the gene for the favourable characteristics
• to the next generation
• And over many generations the favourable characteristic becomes more
frequent
in the population
• each population became different from the other
• over time - genotypically
• and phenotypically
• Even if the populations were to mix again
• they would not be able to reproduce/interbreed with each other
The anole lizard of the Caribbean Islands represents a group of about 150 closely
related species, which evolved within the past 50 million years from a single
species. Use this example to describe how natural selection led to the process of
speciation that gave rise to the 150 different species of lizards.
Natural selection and speciation
• The original species of anole lizards was separated
• Into different populations
• by a geographical barrier
• which is the sea
• There was no gene flow
• between the separated populations
• Each population was exposed to different environmental conditions
• on each island
• Because there is variation
• amongst the lizards
• Natural selection occurred independently
• in each population
• Some had favourable characteristics
• to survive on a specific island
• while others did not
• The ones that did not have the favourable characteristics died
• The ones with the favourable characteristic survived
• and reproduced to pass the gene for the favourable characteristics
• to the next generation
• And over many generations the favourable characteristic becomes more
frequent
in the population
• each population became different from the other
• over time - genotypically
• and phenotypically
• Even if the populations were to mix again
• they would not be able to reproduce/interbreed with each other
