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Session 5. Variation, Adaptation, and Natural Selection
Learning Goals
During this session, you will have an opportunity to
build understandings to help you:
- Recognize how populations vary with regard to inherited
traits
- Distinguish between DNA, chromosomes, and genes
- Relate genes to
variation in populations
- Describe the process
of adaptation through natural selection
Video Overview
How is it that life always seems to find a way? Changes – both
large and small – are ever-present in the environment that surrounds
life. But despite sometimes extreme challenges to survival, life
forms persist from generation to generation. In the last two sessions,
we
focused on life cycles and their connection to DNA, and we began
to look at life at the level of populations. The next two sessions
build
upon this as we focus on the fundamentals of evolution: How populations
change over time and how this can lead to new life forms. Session
7 starts with an exploration of variation, adaptation, and natural
selection.
View this video==> 
Video Outline
Where do we find variation in the living world? Our Bottle Biologist,
Dr. Paul Williams, switches hats for
this program. As the developer of Wisconsin Fast Plants, he has
firsthand experience observing
variation and how it provides the raw material for change in populations
over
time. Using the curriculum resource Exploring
with Wisconsin Fast Plants, the sixth graders in Dr.
Kathy Vandiver’s
class in Lexington, Massachusetts assess variation in plant height
and think about
its causes.
Dr. Robert Murray and Dr. Georgia Dunston,
of the National Human
Genome Center, introduce us to the role of genes as
a source of variation. We hear of one example that applies to humans – PTC
tasting – and
we are presented later with a scenario where the ability to taste
PTC is an advantage that leads to change in a population. The role
of genes is emphasized as mutation is introduced as one cause of
new variation in populations.
As a contrast to natural selection,
Dr. Williams describes how he developed Fast Plants through artificial
selection. A bit of
evolutionary history is next highlighted as we introduce Charles
Darwin’s contributions and focus on the meaning of adaptation through natural
selection. Throughout the program, we visit the Science Studio
where a new group of children composed of fourth and fifth graders
give
us insight into children’s ideas.
And Bottle Biology returns
as Dr. Williams features a bottle system for studying the fundamentals
of evolution.
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