Download Unit 1 Evolution and nat selection and

8/11
• Good Afternoon 
• Please turn in your Natural Selection
Simulation… don’t forget to turn in the packet,
2 graphs, 2 paragraph summaries, and 3
discussion questions.
• Please remove all hats and put electronics
away.
Good morning 
• Please pick up an
iRespond remote.
• Turn in your evidence
for evolution webquest.
• Get ready for your quiz!
Evolution and Natural Selection
How did life evolve on Earth?
What is Evolution?
-Evolution is the gradual
change in a POPULATION
over a long period
of time.
Evidence of Evolution
1) Fossils
– Found in sedimentary rock
layers (strata)
– Fossils found deeper very
different from fossils found
closer to surface
– Relative dating- idea that
fossils found deeper are
older
– Radiometric dating- A
fossil’s carbon14 can be
measured to determine
actual age
– Fossils have revealed
changes in organisms over
time and provide clues to
changes in climate.
Evidence for Evolution
2) Biogeography
- We can compare island
species with their
mainland ancestors
- Ex: Darwin’s discovery
of a species of finches
in the Galapagos Islands
Evidence of Evolution
3) Homology- Similarity in
characteristics of different
species resulting from
common ancestor
-homologous structures: same
structure, different function
Evidence for Evolution
4) Vestigial structures:
structures that have a
reduced or no function
today, but had a function
in a common ancestor
Evidence for Evolution
5) Embryological- if the
embryonic development
was similar then this may
indicate a close
relationship and common
ancestor
Evidence of Evolution
6) Biochemical Evidence: if
two species have similar
DNA sequences then
they may have common
ancestor (most reliable
source)
What is Natural Selection?
• A process in nature that only the organisms
best adapted to their environment tend to
survive and pass on the surviving traits to
their offspring.
• It is a key mechanism of evolution.
Natural Selection
1.
2.
3.
4.
5.
Individuals within a population
vary in their traits.
More offspring are produced
than can survive. Many will get
eaten or will not be able to
compete for resources.
There is competition for limited
resources that creates a struggle
for existence.
Individuals with advantageous
traits will survive and reproduce.
Those with bad traits will die,
taking those bad traits with
them.
Concept was called survival of
the fittest by Herbert Spencer
after Spencer read Darwin’s
book, On the Origin of Species.
• Natural Selection of
“the best” traits leads
to EVOLUTION.
What an Adaptation IS and IS
NOT…
• An adaptation is a trait
that an organism is
born with/has
genetically that better
enables it to survive in
an environment.
– Ex: webbed feet on a
duck
• An adaptation is NOT
acquired during an
organism’s lifetime.
What are two types of evolution?
Divergent Evolution:
• When a species
diverges into 2 or more
descendant species
which results in once
related species
becoming more and
more dissimilar.
What are two types of evolution?
Convergent Evolution
– Unrelated species evolve
similar traits even though
they live in different parts
of the world.
– Similarity in environment
has led to evolution of
similar traits.
– EX: Madagascar aye-aye
and New Guinea striped
opossum both have
elongated middle fingers.
Live separately but have
same structure
What is Speciation?
• Species: group of individuals that
actually or potentially interbreed in
nature.
• Speciation: process of one species
splitting into two species. Usually
due to a geographic divide that
separates the species.
– Ex: Kaibab squirrel and Abert
squirrel were once the same
species but were divided by
creation of Grand Canyon.
• Phylogenetic Trees show
evolutionary relationships among
organisms.
• They also show how they evolved
from a common ancestor