MeegsC CC 3.0
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Natural Selection in Finches
Key Question: How did studying Galápagos finch beaks provide evidence for evolution by natural
selection?
► Natural selection acts on the phenotypes of a population. Individuals with
phenotypes that
increase their fitness produce more offspring
, increasing
the
proportion of the
genes corresponding to that phenotype
in the next generation
.
▸ Numerous population studies have shown that natural selection can cause
selection on a population can be verified by making quantitative measurements
phenotypic changes in a
population relatively quickly. The effect of natural
of phenotypic traits.
Beak adaptations and feeding in Galápagos finches
The beaks of the warbler
finches are the thinnest of the
Galapagos finches. They are
used to spear insects and probe
flowers for nectar.
G.fortis
The cactus ground finches have
evolved probing beaks to extract
seeds and insects from cacti.
The five species of tree
finches are largely arboreal
(tree dwelling). Their sharp
beaks are well suited to
grasping insects which form
the bulk of their diet. The sharp
beaked finches use tools to
extract insects.
Genus
Finch
Beak type
Diet
Putneymark CC 2.0
Certhidea
Warbler finches
Sharp beaked
tree finches
Camarhynchus,
Tree finches
Grasping beak
Tool use
Insect eaters
Sharp beaked
ground finches
Probing beak
Cactus finches
Nectar,
blood
Cactus
Seeds
Putneymark CC 2.0
Geospiza
Ground finches
Crushing beak
Platyspiza
Vegetarian
finch
Parrot-like
beak
Fruit eater
Vegetarian finches feed on
buds, leaves, flowers, and fruit.
Their parrot-like beaks are
evolved for food manipulation.
Ground finches have crushing type
beaks for seed eating. The finches differ
mainly in body size and in the size of
their beaks
1. What are the main factors that contributed to the adaptive radiation of the Galápagos finches?
A