1. UNIT 7 - Evolution
“TO BE OR NOT TO BE”

2. EVOLUTION
 Definition:
 evolution is any change in the frequency of an
allele in a gene pool
 Theory – a collection of carefully reasoned
and tested hypothesis about how evolutionary
change occurred

3. I. Ancient Earth
 A. Atmospheric Conditions (pg 342)
 1. Gases (notice no oxygen)
• Large %
 Carbon dioxide (CO2), Nitrogen (N2), Water vapor
• Small %
 Methane(CH4), Ammonia(NH3), Hydrogen Sulfide (H2S)
 2. Miller -Urey Experiment
• Synthesized complex organic molecules by mixing
and electrically stimulating a mixture gases (pg 344)
• Urea, acetic acid, amino acids, lactic acid, adenine,
ATP were produced

4. I. Ancient Earth
 3. Other Experiments
 No oxygen in mixture allowed the formation of
• Polypeptides - amino acids linked together

5. I. Ancient Earth
 B. The First Cells –
 3.5 bya - anaerobic, prokaryotic (like today’s
bacteria), heterotrophic, high competition for food
 3.4 bya – autotrophic, probably photosynthesis with
H2S instead of water
 2.2 bya – modern photosynthesis, use H2O, releasing
O2 into the atmosphere, ozone layer formed
 1.5 bya – eukaryotic cells, sexual reproduction,
increased genetic diversity
 1.3 bya – multicellular organisms

6. I. Ancient Earth
 C. Age of the Earth
 1. Formation of Earth - 4.5 billions years ago
 2. Relative dating - geologic time scale (pg 23 UP)
 3. Absolute dating - half-life
• Half-life = time it takes for 1/2 of a radioactive
substance to decay (breakdown)
• Carbon-14 1/2 life = 5770 years
• Potassium-40 1/2 life = 1.3 billion years

7. II. Evolution
 D. Evidence for Evolution
 1. Fossil record (pg 278)
• Fossils are any preserved remains or evidence of
an ancient organism
• Examples - insects in amber, frozen mammoth,
petrified wood or bones, imprints in rock
• Not complete - many organisms do not become
fossilized
• Not all specimens are the same quality
• Record does indicate what did live at different times
• Record does show that living things changed with
changes on the Earth

8. II. Evolution
 D. Evidence for Evolution
 2. Living organisms
• Embryology - development of embryos very similar
in different species
• Body Structure
 Homologous structures - bones in the legs and arms of
vertebrates are very similar in structure but not always
function(lab 38)
 Vestigial organs - organs that remain in an organism but
seem to have no obvious function
• leg bones in pythons, muscles that move the ears in
humans, appendix in humans
• Biochemistry - similar chemicals found in living
things, DNA sequence, blood antigens (lab 28)

9. III.Theories of Evolution
 A. Lamarck
 1. Desire to change
• Animals changed in structure because of a desire to
improve
• Giraffe’s necks got longer because they stretched to
get the leaves at the top branches,
 2. Use and Disuse
• Use it or lose it - through disuse things would be lost
 3. Acquired characteristics were inherited
• Any changes in the adult were passed on to the
offspring
• Example - stretched necks of adult giraffes were
inherited by young

10. Darwin

11. III.Theories of Evolution
 B. Darwin
 1. Overproduction of offspring
• Organisms tend to produce more offspring than
needed to replace numbers
 2. Struggle for existence
• Competition for resources is always present
• Predation always present
 3. Variations in populations exist
• Differences in structure exist at birth not acquired
• These variations are inherited from the parents

12. III.Theories of Evolution
 C. Natural Selection
 1. Definition - the organisms that are best suited for the
present environmental conditions will survive to
reproduce therefore passing on their characteristics to
their offspring
• “Survival of the Fittest” - not necessarily the strongest or
fastest.
 2. Conditions that help
• Mutation - source of variation in genes
• Gene flow - genes moving between populations
 3. Adaptations
• - traits that survive from one generation to the next
 4. Example - Peppered Moth / industrial revolution in England
• Two phenotypes for moth = Black and speckled
• When the bark of the trees got discolored the population changed from mostly
speckled to mostly black

15. Span worm Wandering leaf insect Bombardier beetle Foul-tasting monarch
butterfly
Poison dart frog Viceroy butterfly mimics When touched, the
Hind wings of io moth snake caterpillar
monarch butterfly
resemble eyes of a changes shape to look
much larger animal like the head of a snake
Figure 8-11
Page 177
Slide 18

16. IV. Types of Evolution
 A.Microevolution - changes that take place
within a single species to form variations in
populations.
 B.Macroevolution - changes that have
taken place in a species that leads to two
or more different species (common
descent)

17. IV.Types of Macroevolution
 1. Gradualism
 One species gradually changes into a new species
 2. Divergent Evolution or Speciation
 a. Definition - the development of two or more
species from a common ancestral species
• Adaptive radiation - a habitat opens up that permits many
new niches to be occupied allowing many variations to
survive.
 b. Processes that need to occur
• Geographical isolation - members of a species is
separated from others due to physical barriers
 Mountain ranges, oceans, canyons
• Reproductive Isolation - species are separated by the
ability to reproduce
 Mating behaviors, physical structures, genetic make-up

18. IV.Types of Macroevolution
 3. Punctuated equilibria
 Tempo of speciation: gradual vs. divergence in rapid
bursts; Eldredge and Gould (1972); helped explain the non-
gradual appearance of species in the fossil record

19. IV.Types of Macroevolution
 4. Convergent Evolution
 a. Definition - when two separate species
develop similar adaptations (phenotypes)
through different evolutionary trees
 b. Examples
• Sharks and dolphins (pg 21 in UP)
• mimicry

20. V.Human Evolution
 Pages 34,35,61 in UP