Do Now

1
Do Now!

• Why do we have pedigree charts? How is it read?
• Wild type refers to? Is this disease a
  recessive or dominant type? Explain
• What is evolution? Why did it occur?

Homework Text assessments 1 and 2 also,
complete through similarities in early
development see website
2
Evolution

• Charles Darwin and Natural Selection

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Vocab

• Evolution - change in a kind of organism over
  time process by which modern organisms have
  descended from ancient organisms
• Theory - well-tested explanation that unifies a
  broad range of observations

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Voyage of the Beagle (1839 - 1844)

• Darwins Voyage - During his travels, Darwin made
  numerous observations and collected evidence that
  led him to propose a revolutionary hypothesis
  about the way life changes over time. What was
  it?

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Galapagos Islands

• During his travels, Darwin was amazed how
  different organisms were so well adapted to many
  different environments. (Perfect fit)
• He saw patterns of diversity
• Not just in living organisms, but also in fossil
  records.
• The Galapagos Islands were a microcosm of
  Evolution

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Darwins Finches
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Ideas that shaped Darwins Thinking

• James Hutton and Charles Lyell helped scientists
  recognize that Earth is many millions of years
  old, and the processes that changed Earth in the
  past are the same processes that operate in the
  present.
• Thomas Malthus (English Economist) - reasoned
  that if the human population continued to grow
  unchecked, sooner or later there would be
  insufficient living space and food for everyone.
• Jean-Baptiste Lamarck 1809 - proposed that by
  selective use or disuse of organs, organisms
  acquired or lost certain traits during their
  lifetime. These traits could then be passed on to
  their offspring. Over time, this process led to
  change in a species

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Lamarck (His theory is wrong)

• Tendency Toward Perfection
• Innate tendency toward complexity and perfection
• Birds acquired the urge to fly
• Kept trying to fly
• Use and Disuse
• Using a trait (wings) causes them to become
  stronger and larger
• Disuse causes it to disappear
• Inheritance of Acquired Traits
• Passing acquired traits from one generation to
  the next

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Lamarck
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Two things to know before talking about Natural
Selection

• In our world there is
• Natural Variation - differences among individuals
  of a species
• And in order to understand Natural Selection you
  need to understand
• Artificial selection - selection by humans for
  breeding of useful traits from the natural
  variation among different organisms. Do you
  remember the term we used for this beforehand?

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Vocab

• struggle for existence - competition among
  members of a species for food, living space, and
  the other necessities of life
• Fitness - ability of an organism to survive and
  reproduce in its environment
• Adaptation - inherited characteristic that
  increases an organisms chance of survival
  (increases an organisms fitness)
• survival of the fittest - process by which
  individuals that are better suited to their
  environment survive and reproduce most
  successfully also called natural selection

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Natural Selection

• is the process by which individuals that are
  better suited to their environment survive and
  reproduce most successfully also called survival
  of the fittest
• In order for natural selection to occur there
  must be
• Natural Variation
• Struggle for existence
• An adaptation that increases the fitness of one
  organism over another

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Descent With Modification

• Darwins proposed that over long periods natural
  selection produces organisms that
• Have different structures
• Establish different niches
• Or occupy different habitats
• As a result species have descended, with changes
  from other species over time.
• Darwins principle of Descent with modification

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Do Now - Questions

• Key Concept What idea(s) from geology were
  important to Darwins thinking?
• Key Concept According to Lamarck, how did
  organisms acquire traits?
• Key Concept According to Malthus, what factors
  limited population growth?
• Why has Lamarcks theory of evolution been
  rejected? Create an example to illustrate this!
• Have notebook/guided notes/homework out!
• Purpose Learn more about the evolution of
  evolution!
• Homework see the website!!!

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Evidence of Evolution
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The Fossil Record
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Geographical Distrib. of Species
Common Descent
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Homologous Body Structures

• vestigial organorgan that serves no useful
  function in an organism

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Vestigial Organ

• organ that serves no useful function in an
  organism

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Similarities in early development
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Summary of Darwins Theory

• There is variation (genetic)between organisms
  which can be inherited.
• Organisms in nature produce more offspring than
  can survive, and many of those that survive do
  not reproduce.
• Because more organisms are produced than can
  survive, members of each species must compete for
  limited resources.
• Because each organism is unique, each has
  different advantages and disadvantages in the
  struggle for existence.
• Individuals best suited to their environment
  survive and reproduce most successfully. The
  characteristics that make them best suited to
  their environment are passed on to offspring.
  Individuals whose characteristics are not as well
  suited to their environment die or leave fewer
  offspring.
• Species change over time. Over long periods,
  natural selection causes changes in the
  characteristics of a species, such as in size and
  form. New species arise, and other species
  disappear.
• Species alive today have descended with
  modifications from species that lived in the
  past.
• All organisms on Earth are united into a single
  tree of life by common descent.

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Chapter 16

• GENES
• and VARIATION

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Darwins Ideas Revisited

• Darwins ideas had to be integrated with our new
  found information on Genetics.

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Genes and Variation

• Gene Pools - combined genetic information of all
  the members of a particular population
• Relative Frequency - number of times an allele
  occurs in a gene pool compared with the number of
  times other alleles occur

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Genes and Variation

• There are two main sources of genetic variation
• Mutations
• What are the two main types of mutations?
• Gene shuffling
• When and how does gene shuffling occur?
• Big question Do mutations and gene shuffling
  cause evolution? In other words do mutations and
  gene shuffling change the relative frequencies of
  alleles in a gene pool?

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Genes and Variation

• single-gene trait - trait controlled by a single
  gene

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Genes and Variation

• polygenic trait - trait controlled by two or more
  genes

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Genetic Change (Evolution)

• Big Question
• Since mutations and gene shuffling does not
  change the relative frequencies of alleles in a
  population, what causes the change of allele
  frequencies in a population?

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Single-gene Trait (Natural Sel.)

• Natural selection on single-gene traits can lead
  to changes in allele frequencies and, thus, to
  evolution.

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Homework

• Handout 16-1 and 16-2
• Thursday

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• What two processes can lead to inherited
  variation in populations?
• How does the range of phenotypes differ between
  single-gene traits and polygenic traits?

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Polygenic Traits (Natural Sel.)

• Natural selection can affect the distributions of
  phenotypes in any of three ways
• directional selection form of natural selection
  in which the entire curve moves occurs when
  individuals at one end of a distribution curve
  have higher fitness than individuals in the
  middle or at the other end of the curve
• stabilizing selection - form of natural selection
  by which the center of the curve remains in its
  current position occurs when individuals near
  the center of a distribution curve have higher
  fitness than individuals at either end
• disruptive selection - form of natural selection
  in which a single curve splits into two occurs
  when individuals at the upper and lower ends of a
  distribution curve have higher fitness than
  individuals near the middle

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Directional Selection
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Stabilizing Selection

• Stabilizing selection
• takes place when individuals near the center of a
  curve have higher fitness than individuals at
  either end. This example shows that human babies
  born at an average weight are more likely to
  survive than babies born either much smaller or
  much larger than average.

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Disruptive Selection

• What will Disruptive Selection result in?

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Genetic Drift

• Genetic Drift - random change in allele
  frequencies that occurs in small populations
• In small populations, individuals that carry a
  particular allele may leave more descendants than
  other individuals do, just by chance. Over time,
  a series of chance occurrences of this type can
  cause an allele to become common in a population.
  
• founder effect - change in allele frequencies as
  a result of the migration of a small subgroup of
  a population

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Genetic Drift and Founder Effect
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Does Evolution occur all of the time?

• NO

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Hardy-Weinberg principle

• The principle that allele frequencies in a
  population will remain constant unless one or
  more factors cause the frequencies to change
• If there are no factors causing allele
  frequencies to change then the population is
  in..
• genetic equilibrium - situation in which allele
  frequencies remain constant

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Genetic Equilibrium

• Five conditions are required to maintain genetic
  equilibrium from generation to generation
• random mating
• the population must be very large
• there can be no movement into or out of the
  population
• no mutations (that filter into the gene pool)
• no natural selection

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Homework

• Studyguide 16-3
• Test Chapter 15 and 16 on Tuesday

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• Describe how natural selection can affect traits
  controlled by single genes.
• Describe three patterns of natural selection on
  polygenic traits. Which one leads to two distinct
  phenotypes?
• How does genetic drift lead to a change in a
  populations gene pool?
• What is the Hardy-Weinberg principle?

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When evolution DOES OCCUR

• The process of SPECIATION - formation of new
  species
• Speciation has occurred when population have
  become reproductively isolated from one another
• reproductive isolation - separation of species or
  populations so that they cannot interbreed and
  produce fertile offspring
• Reproductive isolation can develop in a variety
  of ways, including behavioral isolation,
  geographic isolation, and temporal isolation.

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Behavioral Isolation

• form of reproductive isolation in which two
  populations have differences in courtship rituals
  or other types of behavior that prevent them from
  interbreeding
• Examples
• Mating calls
• Mating dances

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Geographic Isolation

• form of reproductive isolation in which two
  populations are separated physically by
  geographic barriers such as rivers, mountains, or
  stretches of water

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Temporal Isolation

• form of reproductive isolation in which two
  populations reproduce at different times

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Speciation of Darwins Finches

• Speciation in the Galápagos finches occurred by
  the
• founding of a new population
• geographic isolation
• changes in the new populations gene pool
• reproductive isolation
• ecological competition