This document provides an overview of evolution and related topics. It defines evolution as any change in allele frequencies in a gene pool over time. The ancient Earth had an atmosphere without oxygen which allowed for the formation of complex organic molecules like amino acids. The first cells were anaerobic and prokaryotic around 3.5 billion years ago. Evidence for evolution includes the fossil record, similarities in living organisms, and DNA/biochemical evidence. Theories of evolution include Lamarck's theory of acquired characteristics and natural selection proposed by Darwin involving variation and the survival of the fittest. Evolution can occur through microevolution within a species or macroevolution leading to new species through gradualism, divergence, or convergent evolution.

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