Darwin and Evolution
Chapter 15
Objectives
 Identify historical figures and their viewpoints before and during the
development of Darwin’s theory.
 Summarize the process of evolution through natural selection.
 List examples of evidence that support shared ancestry
 Give examples of how evolutionary change can be studied
 Give an example of supporting evidence of evolution for each area of its
study.
 Interpret misconceptions of evolution.
Misconception:
 Evolution is a theory about how
life originated.
Truth:
 Evolution deals with how the
diversity of life emerged following
the origin of life.
Misconception
 There are no transitional fossils.
Truth
 There are transitional fossils.
 Scientists cannot expect to find a
transitional fossil for every species
because the process for a fossil to
be formed is very specific.
Misconception
 Evolution proposes that life
changed as a result of random
events; traits are much too
complex to have come about
“by chance”
Truth
 Mutations create new variation in
populations randomly.
 Natural selection can only act
upon variations existing in the
population.
 Complexity resulted from millions
of years of modifications on
existing traits.
Misconception
 Evolution is not observable or
testable; thus, it is not science.
 Evolution is both observable and
testable.
 Evolution has 150 years of
supporting evidence from a wide
variety of scientific disciplines.
 New variation can arise from small
changes to single genes.
 Population traits change in
response to environmental
changes.
Evolution
 Evolution is change over time.
History of Evolutionary Thought- Mid
18th Century Influences
 Plato- Organisms have an “essential” form and variation on that form gives
rise to species
 Aristotle- organisms vary in complexity
 Count Buffon- described all known plants and animals and proposed
environmental influence and the struggle for existence as evidence for
evolution
 Linneaus- believed in the fixity of species and developed a binominal
nomenclature system
 Erasmus Darwin- believed species evolved but did not offer a mechanismbased his conclusions on vestigial structures, developmental changes of
animals, and animal breeding by humans.
History of Evolutionary Thought- Late
18th/Early 19th Century
 Baron Georges Cuvier-Proposed the theory of catastrophism.
 Lamarck- inheritance of acquired traits
 Hutton- proposed the theory of uniformitarianism
 Malthus- proposed that the human population size is limited by the quanity
of resources
Darwin’s Theory of Evolution
 Darwin Studied at Christ’s College with the intent of becoming a clergyman
 Served as a naturalist aboard the HMS Beagle for 5 years to explore the Southern
Hemisphere
Observations of Change over Time
 Observed long spans of beaches strewn with fossils
 Saw marine shells high upon mountains
 Began to accept that possibility of the Earth being very old
 Descent with modification could occur
Biogeographical Observations
 Geographical distribution of species provide evidence and hints for past
geological events.
 Similar environments on different continents have similar looking organisms.
 Differences among organisms was correlated with variations in the
environment
Natural Selection
 Organisms exhibit heritable variation.
 We now know about genes and mutations. Genetic mutation can be helpful, harmful, or neutral. It is
random. Helpful and harmful traits are maintained in a population.
 Because the natural selection is random and beneficial mutations have greater reproductive successthere is no goal of improvement in anticipation of future changes
 Organisms compete for natural resources
 Fitness is reproductive success relative to other population members.
 Individuals within a population differ in terms of reproductive success.
 The more fit, the more resources, the more chances to reproduce and pas on traits.
 Organisms adapt to conditions as their environment changes.
 An adaptation is any evolved trait that helps an organism be more suited to its environment.
 Differential reproduction in subsequent generations increases frequency of traits adapted to an
environment
 https://youtu.be/0SCjhI86grU
Artificial Selection
 Artificial selection provides the ability to see selection at work.
 Plants
 Dogs
 Peppered-Moths
 Bacterial Resistance
Evidence for Evolution
 https://youtu.be/lIEoO5KdPvg
Evidence for Evolution- Fossils
Evidence for EvolutionBiogeographical
Evidence for Evolution- Anatomical
Evidence for Evolution- Biochemical
Evidence for Evolution- Developmental
Biology