Page 179 - Big Ideas Year 10 sciPAD 2025

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SCIPAD - BIG IDEAS - BOOK 2
THE BASIS OF HEREDITY
Variation in Beak Length of Ancestral Kiwi
Number of individuals
Shorter beaks
Beak Length
Longer beaks
(a) What do kiwis eat? 
(b) Which ancestral kiwis would have been the most successful in obtaining this food?

(c) Would the alleles for short beaks or longer beaks be more likely to be passed on to
the next generation? 
(d) What would you expect to happen to the length of kiwi’s beaks over time?

Scientists have completed DNA studies on the finches and determined that Darwin was correct.
The Galápagos finches are descended from finches found almost 1 000 km away in Ecuador.
When the ancestral finches arrived in the Galápagos, there would have been a small amount
of variation in their beak size. The ancestral finches are thought to look similar to modern day
Grassquits.
8. Using the word list provided, complete the following paragraph.
evolved - alleles - thickest - variation - finches - thicker - breeders - beaks - thousands
When the first group of arrived on the Galápagos Islands, there would have
been in their beak size. Some finches would have had thinner beaks,
and some would have had beaks. If they arrived on an island where
the main food source was seeds with hard shells, then the finches with the
beaks would have access to more food. These finches would have been the most successful
and therefore, passed on their for slightly
thicker beaks. The next generation of finches would still have variation in their beak size, however,
there would be more finches with genes for thicker . If this process was
repeated over of years, it could explain how the large, thick beak
of the ground finch from the small, thin beak of the ancestral finch.
A modern Grassquit closely resembles the
ancestor of the Galápagos finches.
A modern day Large Ground Finch from the
Galápagos islands.
Explaining the Evolution of the Large Ground Finch (a seed eater)
9. It is thought that the ancestor to the kiwi was a short-beaked bird and this beak has evolved
over time to the narrow slender beak we currently see on modern kiwis.
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