Transcript Evidence of Evolution - Sonoma Valley High School

Evidence of Evolution
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Dating Rocks
• Relative dating: using
the position of the
rocks in the rock layer
to determine which are
older (superposition)
• Absolute dating:
Using the decay of
isotopes to determine
a more precise age of
rocks (radiometric
dating)
Radiometric dating
• Radiometric
dating: is a measure
of the decay of isotopes
•Isotopes decay at a known rate
called Half-life.
•Half-life is the amount of time need
for ½ of a sample of radioactive
material to decay
•The age of a rock can be calculated
using the formula:
•time = duration of half-life X # of
half-lives that have occurred.
Calculating rate of decay
• Each isotope has a known half-life.
– For example the half-life of Iodine-131 is 8.1
days.
• The number of half-lives passed can be
calculated by knowing what fraction of the
parent isotope is remaining.
– ½ remaining = 1 half life, ¼ = 2, 1/8 = 3 etc.
test yourself: If there is ¼ of iodine-131
remaining how much time has passed?
2 x 8.1days = 16.2 days
Types of evidence
•
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Fossil record
Transitional species
Homologous structures
Vestigial structures
•Biological molecules:
DNA, RNA, proteins
•Embryology
•Antibiotic resistant
bacteria
Fossil record & transition
species
• Transitional fossils
• Darwin predicted they
would be found.
• Links today’s forms
with ancestral form.
• Birds/reptiles
• Land/sea mammals
• Four legged animals
with fish.
what do you think this fossil is a
link to?
Homologous Structures
• Different shape
and function today.
• Same evolutionary
origin.
– Ex: Bones of the
forearm of
mammals.
Vestigial Structures
• Structure is coded
for in the DNA.
• Function has
apparently been
lost.
– Ex: Human
appendix?
Similar macromolecules
– Related species have the
same or very similar
DNA and proteins.
– Distantly related
organisms have dissimilar
DNA and proteins.
– Vital genes and proteins
change little over time.
(conservative traits)
– Universality of genetic
code
What more closely related a
pigeon and a monkey or a
pigeon and a bull frog?
Similarity in Embryology
• Embryos of
similar
species
look the
same.
• Embryos of
related
species go
through
the same
steps.
Antibiotic resistant
bacteria
• Evolution is
continuous
• Bacteria that are
resistant to
antibiotics will
survive when
those that are not
won’t
– Thereby passing
on antibiotic
resistant genes
In your summary answer these questions, pick
one cartoon to explain, and explain how
antibiotics relate to evolution.
1. What is an homologous structure?
2. How are embryos evidence of evolution?
3. Name a way to show species are closely
related.