Transcript Slide 1 - Dr. Tricia Britton

Chapter Thirteen: Evolution
• 13.3 Natural Selection
13.3 Natural Selection
• Adaptations are changes that enable an
organism to survive environmental changes.
• Adaptations are inherited- that is- passed
from one generation to the next .
Bill Nye 100 greatest discoveries
•
http://www.sciencechannel.com/tv-shows/greatest-discoveries/videos/100-greatest-discoveries-shortsnatural-selection.htm
• What was driving force behind all life?
(answer this question- listen to the video)
Mutations
• Since Darwin’s time, there has been a growing
body of knowledge about heredity.
• Today, scientists know that variations in the
population of a species are caused by random
mutations in genes.
• Random mutations in genes produce
variations of traits in a population.
13.3 The importance of
genetic variation
• Some mutations are harmful
because they cause genetic
disorders.
• Mutations may also be helpful
because they contribute to
genetic variation.
• Page 272 for picture
A mutation story
•
http://www.pbs.org/wgbh/evolution/library/01/2/quicktime/l_012_02.html
•
Listen to the video and answer….
• What is the name of the trait?
• From what disease does this protect humans?
The importance of genetic variation
• Genetic variation refers to the variety of
alleles in a population.
• Genetic variation is necessary for natural
selection and ensures that a population has a
better chance of survival should the
environment change.
How a new species evolves
• One way for a species to evolve happens in 3
steps:
1) Isolation
2) Adaptation
3) Differentiation
See page 273
How a new species evolves
1) Isolation happens when a population
becomes divided by an event such as storms,
floods, volcanic eruptions, earthquakes. The
original population becomes divided into
smaller populations.
2) Adaptation
3) Differentiation
How a new species evolves
1) Isolation
2) Adaptation happens through natural
selection. The event that causes isolation
may also change the environment. The
separated populations must adapt to their
environments. Each population will have
different adaptations.
3) Differentiation
How a new species evolves
1) Isolation
2) Adaptation
3) Differentiation happens when the isolated
populations become so different that they
can no longer interbreed. Over many
generations, the populations become
genetically different. One or more new
species is formed.
13.3 Extinction
• Extinction occurs when the
environment changes and
the adaptations of a
species are no longer
sufficient for its survival.
13.3 Extinction
• The dodo bird is an example of
how human impact may
contribute to extinction.
• The dodo was first sighted
around 1600 on Mauritius, an
island in the Indian Ocean.
• The dodo was extinct less than
eighty years after its discovery.
Why does evolution matter now?
• http://www.pbs.org/wgbh/evolution/library/11/2/quicktime/e_s_6.html
• Listen to the video and answer these questions.
• What disease is the subject of this video clip?
• What are symptoms people have?
• What is the adaptation of this bacterium that
allows it to survive? __________