Download Natural Selection An adaptation is an inherited characteristic that

Bio07_TR_U05_CH15.QXD
5/5/06
1:44 PM
Page 8
Name______________________________
Class __________________
Date ______________
Natural Selection
An adaptation is an inherited characteristic that helps an organism
survive and reproduce in its environment. Over time, adaptations
become more common in the population. For example, suppose
that the water in a pond gets darker over a period of four years.
The table below shows what might happen to a frog population
living in the pond.
Look at the pictures showing how a population of frogs changed over time.
Year 1
Year 2
Year 3
Year 4
Complete the table.
Year
Light-Colored Frogs
Dark-Colored Frogs
1
2
3
4
Use the table to answer the question.
1. How did the numbers of light- and dark-colored frogs change
over time?
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Bio07_TR_U05_CH15.QXD
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Name______________________________
Class __________________
Date ______________
The Fossil Record
In the fossil record, an intermediate form is a fossil that shows
some characteristics of an earlier related organism and some
characteristics of a later related organism. The illustrations below
show organisms whose fossils make up part of the fossil record.
The organisms are in order from oldest (organism 1) to most recent
(organism 4).
Draw an animal that might have been an intermediate form between
organism 1 and organism 2. Then, draw an animal that might have
been an intermediate form between organism 3 and organism 4.
Organism 1
Organism 3
Organism 2
Organism 4
Use the illustrations to answer the questions.
1. Describe one change you see between organism 1 and
organism 2.
2. How might these fossils provide evidence for evolution?
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Bio07_TR_U05_CH15.QXD
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Name______________________________
Class __________________
Date ______________
Evidence for Evolution
Use the words below and your knowledge of the evidence for evolution to
complete the table. The first one has been done for you.
fossil record
geographic distribution of living species
similarities in embryo development
Type of Evidence
What It Reveals
homologous body
structures
Animals with different limb structures that
develop from the same embryonic tissues
evolved from a common ancestor.
Vertebrates share a common ancestor, as
shown by how these organisms develop.
Intermediate forms show that organisms
have evolved over time.
Species have adapted over time to
local conditions.
Answer the question.
1. Give an example of homologous body structures.
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