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Bio NOTES: Evolution
Evolution = change over time
= process by which modern organisms
have descended from ancient organisms
HMS Beagle
Charles Darwin added the most to our understanding
of evolution:
 he sailed around the world and observed many organisms
 he saw that many plants and animals were very well suited
to their environment
Darwin learned the most at the
Galapagos Islands.
He saw that the characteristics
Charles
of many animals and plants
Darwin
varied noticeably among the
Galapagos Islands
different islands.
Darwin hypothesized that each organism had adaptations
that allowed them to survive on their particular island.
Natural Selection = individuals best suited to their
environment survive and reproduce most successfully
*natural selection is also known as survival of the fittest*
• Fitness, the ability to survive and reproduce in a given
environment, comes as a result of adaptations.
• Adaptations are inherited traits that increase an organism’s
chance of survival
examples: thumbs, white fur in polar bears,
camouflage
Only the fittest organisms pass on their traits. Because of
this, a species changes over time.
Members of a species have variations –
we now know that these differences come
from mutations in DNA!
We have no control over these mutations!
Polar bears wouldn’t do The environment selects which variations
well in the desert
will be adaptations that help with survival.
Geographic Isolation
 Geographic isolation occurs when two
populations are separated by water or
landforms.
 This geographic separation results in the
formation of new species that differ slightly depending
on the environment.
Adaptive Radiation
-- the process in which one species evolves into diverse
species that live in different ways
Example: Darwin’s finches on Galapagos Islands
More than a dozen species
evolved from a single
species of finch
-- each species adapted to
their environment
Applications of Natural Selection
Pesticide and antibiotic resistance are current issues that
show natural selection at work
Antibiotic Resistance
• some bacteria have mutations that increase their survival
• these mutations cause them to be resistant to antibiotics
• they can pass these traits to future offspring
• this can result in Super Bacteria or Super Bugs
About 70% of hospital infection-causing bacteria are
resistant to at least one type of antibiotic.
Always finish
Some organisms are resistant to
ALL of your
all known antibiotics.
antibiotics!
Pesticide Resistance
• some insects have mutations that increase their survival
• these mutations cause them to be resistant to pesticides
• they can pass these traits to future offspring
Evidence of Evolution:
1. Fossil Record
a) Fossils: preserved remains of ancient organisms
b) TWO types of Fossil Dating (fossil age determination)
Relative Dating
• Based on sedimentary rock layers
• Determines approximate, relative age of a fossil – not the
exact age
Surface
Rock
Layers
Shallow = Recent Fossil
Deepest = Oldest Fossil
Absolute Dating
• Based on the steady decay of radioactive
elements
• Half-Life: Time it takes half a radioactive
element to decay to a new element.
• Carbon-14 has a ½ life of 5,730 years.
• Determines the exact age of a fossil
2. Geographic Distribution of
Living Species
a) The same species of animals,
living in different areas, evolved
based on their surroundings.
3. Shared Anatomical Structures
a) Anatomical structures: body parts, ex: arms, tails, flippers
• Homologous structures: similar body structures
• Vertebrate: has a backbone
b) Similar Anatomical Structures, in 4-limbed
vertebrates, provides evidence of evolution
from a common ancestor.
c) Vestigial Organs: organs or limbs which
have little or no use for an organism.
• Human examples: tailbone, ear
muscles, wisdom teeth, appendix
YOU DON’T HAVE THIS SLIDE!!!!
The muscles
connected to the ears
of a human have lost
most of their mobility.
Letter c in the picture indicates the
undeveloped hind legs of a baleen whale.
Goose Bumps
in humans
are a vestigial
REFLEX; a
reaction to
stress & cold
The blind mole rat has tiny
eyes completely covered by a
layer of skin.
WHY DOES IT HAVE
EYES AT ALL??
4. Biochemical Similarities
a) Biochemical Similarities: Similarities in the Amino Acid
sequence (order) of proteins.
b) The CLOSER an organism’s Amino Acid sequences,
the more likely they are related.
Organism
Amino Acid Sequence
Chimpanzee Serine-Valine-Leucine-Stop
Human
Serine-Valine-Proline-Stop
Fruit Fly
Serine-Lysine-Valine-Stop
5. Embryological Similarities
a) The early embryo stages of all vertebrates
(with a backbone) is very similar.
b) The similarities: embryonic cells develop
in the same order and in similar patterns
in ALL vertebrates.
• Common cells & tissues develop
into homologous (similar) structures.
Questions:
Darwin
1. Who laid the foundations of the Theory of Evolution? ______
2. What is survival of the fittest? _________________________
natural selection
3. What is a trait that increases survival? __________________
adaptation
vestigial
4. What are organs that have little or no use? ______________
5. Embryological similarities compare the ______________
embryos
of
vertebrates.
6. Organisms with similarities such as biochemical,
embryological, & anatomical similarities are thought to have
a common __________________.
ancestor
7. Which type of fossil dating uses the location of the fossil in
the earth to determine the fossils age? ________________
Relative Dating
8. Which type of fossil dating determines the exact age of the
fossil? _______________________
Absolute Dating
9. The half-life of an element is how long it takes the element to
decay to _________
half
its original amount.