2. Darwin’s Theory
EVOLUTION – all changes
that have transformed life
over immense time.
“Evolution is the biological history
of life on Earth”
Before Darwin people thought:
1. species are fixed
-they do not change
2. Earth is less than 10,000 yrs old
https://flic.kr/p/9D76x3
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3. The Changing of Ideas
In the mid 1700’s, his study of fossils caused Georges Buffon
to suggest that the Earth might be much older
He also noticed that some fossils and some living organisms
were similar, but not exactly alike
4. LAMARCK
Proposed that life evolves/changes
It Adapts
Ex: hind legs of a kangaroo
How did massive hind legs of a kangaroo allow them to adapt to the
environment?
Macropus giganteus
https://commons.wikimedia.org/wiki/File:Macropus_major_hind
_legs.png
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6. The Infamous Voyage of
Darwin
Charles Darwin voyaged on the H.M.S. Beagle to the
Galapagos Islands – saw lots of animals, read lots of books,
did lots of thinking – and came up with the following:
7. Darwin
Observed that the Galapagos Islands had many unique
organisms, similar to, but different than those on the
mainland
Also noticed that each island had some organisms that
were not found on any other islands in the chain
Inferred that mainland species had changed after
colonizing the islands, and adapted to their new
environments
8. Mr. Darwin, your thoughts
please?
Organisms Change Over Time
How? Natural Selection!
All organisms can produce more offspring than can survive
There are variations between the individuals in a population
Limited resources = struggle to survive
Individuals with the traits that make them the most “fit” have
better chance of surviving and passing their traits to their children
9. Why is variation important?
Variation allows natural selection to happen
How?
Survival of the fittest- The best adaptation (variation) will
survive and reproduce
Can you think of any other examples of survival of the
fittest? What variation allowed for survival?
Variation Exists within a Species
10. The Backbone of Evolution
Scientists study the fossil record to compare
extinct organisms to modern organisms
The fossil record indicates:
the order in which species emerged
How do we get fossils?
in wet, environments where they can be quickly covered by
sediment
How old are fossils?
Relative dating -top layer must be younger than bottom layer
Radiometric (absolute) dating -use radioactive isotopes- decay
(half life)
11. Analyzing the Present to
Understand the Past-
Evolutionary Support
Comparative Anatomy:
Compare body structures
of different species
Homologous structures:
similar to due to common
ancestry
ex: human arm and whale
flipper
https://www.flickr.com/photos/bibliodyssey/6245974006/galleries/
13. Vestigial Structures:
Remnants of Structures
that may have been useful
in the past, but have little
or no importance now.
Ex. Appendix
Tail Bone
14. Biochemistry: Similarities in
DNA and protein sequences
https://commons.wikimedia.org/wiki/File:Schematic_relations
hip_between_biochemistry,_genetics_and_molecular_biology
.svg
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15. Natural Selection
Explains resistance of insect
populations to pesticides or
bacteria to antibiotics
Spray insecticide
Those that aren’t resistant - die
Those that are resistant - live and reproduce
The next generation contains more resistant individuals - the
population is changing
Adaptation Is a variation, not a change!
‘Colorado Potato Beetle
Public Domain
16. Overuse of antibiotics has lead to strains of bacteria that are
resistant to them.
The bacteria adapted and now have a resistant gene.
Antibiotic Resistance
17. Genetic Drift
Movement of genes in or out of a population
Greatly affects small populations
Geographic Isolation
A barrier separates one population into
two
They evolve different characteristics
They become different species- they
coevolve
