Evolution by Natural
Selection
Objectives:
Key Terms:
— To make predictions about
— Adaptation
finch distribution based on
data given
— To predict changes to
population if factors
change
— To describe what is needed
for evolution to occur
— Variation
— Competition
— Darwin
— Finches
— Evolution
— Natural selection
— Reproduction
— Survival of the fittest.
Variation
Goldfinch
Bullfinch
How do these
of Finch vary?
Whytwo
dospecies
they vary?
Adaptations
Goldfinch
Bullfinch
How are these species of Finch adapted?
Charles Darwin
— Modern ideas of evolution started with Charles
Darwin.
— In 1831 Darwin set out as a ship’s naturalist on
HMS Beagle, it was a 5 year voyage to South
America and the South Sea Islands.
Voyage of the Beagle
— Darwin recorded observations of plants and animals
that he saw on the voyage.
— In the Galapagos islands Darwin observed that each
of the islands had similar types of finches, iguanas
and tortoises, but that each was different to make
the most of local conditions.
Task
— To use the information about the finches and the
food available on each island to predict which
finches will live on which islands.
— You are to work in groups of 2/3.
— If you are finding the task challenging there is a
second information sheet to help you.
Time:
10 minutes
Expectation:
Everyone to complete first
3 finches.
Finch Distribution
What if . . .
The seeds on Espanola started to increase in size?
1. What would you expect to happen immediately to
the population of Small Ground Finches?
2. What would you expect to see happen to the
population over the next 20 years?
3. What would happen if the size of the seeds
decreased again in the future?
Darwin’s Theory
— Darwin only observed one type of finch on the
mainland- similar to the Galapagos Small Ground
Finch.
— He proposed that all finches evolved from the one
species that lived on the mainland.
What factors would have to exist for
a species to be able to change?
— Genetic variation due to mutation.
— Competition; for food, mates, territory, to avoid
predation.
— ‘Survival of the fittest’ the organism that is best
adapted to its environment will survive.
— Reproduction- passing on the advantageous alleles
to the offspring.
— Leading to change in the species over timeevolution.
Exam question (5 marks)
Two different species of butterfly:
Amauris
Hypolimnas
Both species can be eaten by most birds.
Amauris has a foul taste which birds do not like, so birds
have learned not to prey on it.
Hypolimnas does not have a foul taste but most birds do
not prey on it.
Describe, in terms of natural selection, how Hypolimnas may
have developed its wing markings
Mark Scheme:
— Mutation caused changes in marks in Hypolimnas.
— Competition; less predation of butterflies with these
markings.
— These butterflies survived to reproduce; other butterflies
were eaten.
— Advantageous allele/gene was passed on to offspring.
— Over time population of Hypolimnas start to look more
like Amauris; evolution
Remember: make your answer specific to example given.