Transcript the fossil record is not complete!

Evolution Notes
Chapter 10
Evolutionary Terms to Know
 Evolution – change over time
 Microevolution – small changes
over time within a species
 Macroevolution (AKA
Speciation) – over time, groups
of organisms change so much
that they can no longer
reproduce with the original
group
 Adaptation – trait that allows an
organism to survive and
reproduce
 Variation – different traits of
individuals
Evolutionary Terms to Know, cont’d
 Competition – occurs when organisms of the same or
different species attempt to use an ecological resource
in the same place at the same time
 Species – group of organisms that either interbreed or
have the potential to interbreed in a natural
population; offspring are fertile
 Fitness – ability of an individual to survive and
reproduce in its environment
Creation
 In the early 1800’s, most people believed that each
species was created divinely a few thousand years
before, and continued as it was originally created.
Voyage of The Beagle
 Charles Darwin
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Father of Evolutionary Theory
Made observations on a ship called the H.M.S. Beagle
on a voyage to the Galapagos Islands in 1831.
Observations and collected evidences led him to
propose a revolutionary hypothesis about the way life
changes over time.
Voyage of The Beagle
 Darwin’s Observations
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Plants and animals are well suited to environments
Organisms have many ways to survive and reproduce
Similar habitats in separate locations don’t always have
the same animals
Fossils

Collected preserved remains and came up with questions
like:
 Why had these species disappeared?
 How were they related to living organisms?
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Galapagos Islands
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The characteristics of many animals and plants varied
noticeably among the different islands
Voyage of The Beagle
 The Voyage Home
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Studied his collections in detail on the journey home
Because the characteristics of many plants and animals
varied so greatly, he began to wonder if they had once
been members of the same species
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Hood Island Tortoise – long neck (sparse vegetation)
Isabela Island – short neck (vegetation close to the ground)
Pinta Island – intermediate neck (what does this say?)
Other Scientists and their Contributions
 Geology and the Earth

James Hutton (1785)
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Proposed that the Earth is shaped by geological forces that
took place slowly over extremely long periods of time
Estimated that the Earth was millions, not thousands, of
years old
Charles Lyell (1833)
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The Principle of Geology – explained that processes like
earthquakes, volcanic eruptions, erosion, weathering, etc.
have shaped the Earth’s geologic features
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Influences on Darwin:
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If Earth could change over time, could organisms change
as well?
For life to change, the Earth must be extremely old.
Other Scientists and their Contributions, cont’d
 Jean-Baptiste Lamarck (1809)
 By selective use or disuse of organs, organisms acquired or lost
traits, passing them to offspring
 Tendency Toward Perfection
 Organisms change and acquire traits that help them live more
successfully in their environments
 Use and Disuse
 Organisms alter the size or shape of certain organs by using their
bodies in new ways
 Inheritance of Acquired Traits
 If organs are changed in some way, those changes are passed to
offspring
 Evaluating these thoughts
 Didn’t know how traits were inherited
 Didn’t know that behavior has no effect on heritable
characteristics
 One of the first scientists to develop a theory of evolution and
realize that organisms adapt to their environment
Other Scientists and their Contributions, cont’d
Other Scientists and their Contributions, cont’d
 Thomas Malthus (1798)
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If the human population increases faster than the
resources, there would be competition for food and
living space.
Influences on Darwin

Competition certainly applies to animals and plants, since
they produce many more offspring than humans
Other Scientists and their Contributions, cont’d
 Alfred Wallace (1858)
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Independently conceived the theory of natural
selection
Wrote a short essay summarizing his thoughts on
evolutionary changes, which encouraged Darwin to
finally publish The Origin of Species (1859)
Other contributions:
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Identifying the purpose of warning coloration in animals
“Wallace Effect:” natural selection could contribute to
speciation by encouraging barriers
against hybridization
Darwin’s Four Tenets (1865)
Why does Natural Selection Occur?
 Overproduction of Offspring
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More organisms are made than the environment can
support  competition
 Genetic Variation
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There is variation among offspring  preadaptation
 Struggle for Existence
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Natural Selection – survival of the fittest; the
environment selects against traits
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Climate, weather, competition, predators, pollution
How is this different from Artificial Selection?
 Differential Survival and Reproduction

Individuals that have desirable traits are more fit and
leave more offspring
What is Natural Selection?
 The struggle for existence leads to survival of the
fittest (natural selection).
 The “fittest” are those with an inherited
characteristic that makes that individual better suited
to survive and be able to reproduce.
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These characteristics are called adaptations.
What is Natural Selection? Cont’d.
 Natural Selection results in changes in inherited
characteristics of a population due to the
environment, increasing the species’ fitness in that
environment.
 These changes are
observed over long periods
of time and throughout
many generations
Descent with Modification
 Principle of Common Descent:
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All living things are related due to a common ancestor
Evidences for Evolution
 Fossil Record
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Provides evidence about the history of life on Earth
Shows how organisms have changed over time
Most form in sedimentary rock. Layers of sediment
build up over time and dead organisms can be buried.
Trace Fossils – remnants such as footprints or waste
Body Fossils – body parts such as a bone or skull
Evidences for Evolution, cont’d
 Fossils, cont’d
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“Missing Links” – intermediate fossils between groups
of organisms
THE FOSSIL RECORD IS NOT COMPLETE!
Evidences for Evolution, cont’d
 Fossils, cont’d
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Relative Dating – Allows paleontologists to estimate a
fossil’s age by comparing it to other fossils. Based on
the idea that older rock is found under newer rock.
Does not provide exact ages, just estimates.
Younger layers
Older layers
Evidences for Evolution, cont’d
 Fossils, cont’d
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Radioactive Dating – Scientists calculate the age of a
sample based on the amount of radioactive isotopes.
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Carbon-14: is in all living things, but starts to decay
immediately upon death
Carbon-12: is also in all living things, but does not decay
Scientists compare the ratios of these two elements to give
an age of the fossil
Evidences of Evolution, cont’d
 Homologous Structures
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Structures that have different mature forms in
different organisms but develop from the same
embryonic tissues
Provides strong evidence that that all four-limbed
vertebrates have descended, with modifications, from
common ancestors
Evidences for Evolution, cont’d
 Homologous Structures, cont’d
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Analogous Structures – tissues that have the same
function but the species are not necessarily related
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Vestigial Structures – organ that no longer serves any
useful purpose in an organism

EX: The leg bone present in pythons suggests that they
once walked
Evidences for Evolution, cont’d
Evidences for Evolution, cont’d
 Embryology
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Vertebrates have similar embryos
Must mean that there are similar genes at work
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Similar genes indicate a common ancestry
Differences in development are caused by genes that have
mutated during the course of evolution
Evidences for Evolution, cont’d
 Embryology, cont’d
Evidences for Evolution, cont’d
 Biochemistry/Amino Acid Sequences
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The more similar two organisms are, the more similar
their DNA is.
This indicates that certain organisms have evolved
from a common ancestor
EX: conserved sequences in DNA, Hemoglobin, etc.
Evidences for Evolution, cont’d
 Biogeography/Geographic
Distribution of Living Species
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Species evolve differently in
different environments
Darwin discovered that the little
brown birds he collected on his trip
to the Galapagos islands were all
finches; however, they were all
distinctly different
Determined that the finches had a
common ancestor and descended
with modification to their individual
environments