Evolution

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Evolution

• Biology
• Mrs. Volin

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Why do these animals have different means to move
about?
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• Charles Darwin observed traits like these to
  develop his theory of evolution

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Evolution

• Evolution refers to change over time
• Evolution is the process by which modern
  organisms have descended from ancient organisms

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Charles Darwin

• Contributed more toward our understanding of
  evolution than anyone else
• Born in 1809 in England
• Began medical school
• Switched to theological
• school

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Charles Darwin

• Took courses in biology and geology while in
  college
• At age 22, he was invited to sail on a voyage to
  survey South America as the ships Naturalist

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H.M.S. Beagle
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Darwins Voyage1831-1836

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• Darwin collected plant and
• animal specimens at every stop
• How does one explain the immense
• diversity he found?
• 68 beetle species in one day in Brazil
• He noted that organisms were well-suited to
  environments that they inhabited
• He observed that in similar
• habitats, very different
• animals were present

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Darwin found and collected fossils

• Fossils the preserved remains
• of living organisms
• Some resembled organisms that
• were still alive
• Some were unlike any living creatures
• Some of Darwins questions
• Why did some species disappear?
• Were they related to living species?

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Galapagos Islands

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Galapagos Islands

Islands had diverse terrain, very different
climates Variation in species between islands
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Pinta Island
Isabela Island
Hood Island
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Land iguana
Marine iguana
Could these separate species have been members of
the same species?
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14 species
Vegetarian tree finch
Founder
Woodpecker finch
SPECIATION
Insectivorous tree finch
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• Speciation
• the formation of a new species

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14 species
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Ideas that influenced Darwin

• Common beliefs during the time of Darwin
• - Earth was only a few thousand years old
• - All forms of life had been created only a few
  thousand years ago
• - Earth and living species had not changed over
  that time

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Darwins hypothesis

• The animals had a common ancestor
• Ancestor from South America became isolated on
  island
• Over time, species changed to adapt to
  environment of particular island

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Evolution by Natural Selection

• Survival of the fittest
• Individuals best suited to environment survive
  and reproduce
• Natural selection
• Only individuals with certain traits (that give a
  survival advantage) produce new individuals

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The Origin of Species

• Published in 1859
• Thirty years after his voyage on the Beagle
• Darwin explains his theory that life on earth is
  the result of the evolutionary process of natural
  selection

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On Darwin and Religion

• Scientists certainly know more about God than
  the theologians do, for scientists study the
  works of God and the theologians only study what
  has been felt and written about God.
• George
  Gaylord Simpson

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Ideas that influenced Darwin1700s and 1800s

• James Hutton
• Earths features were shaped over long periods of
  time----millions of years
• Charles Lyell
• Earth has been gradually changed by same
  processes that occur even today
• Principles of Geology
• Led Darwin to believe that organisms changed too

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Ideas that influenced DarwinJean-Baptiste Lamarck

• Living things have
• changed over time
• All species have descended
• from other species
• One of first theories of
• evolution
• Published his theory in 1809

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Lamarcks Theory

• Selective use and disuse
• Organisms can alter size/shape of organ by using
  their body in new ways
• Example Bird ancestor uses front limb to try to
  fly---eventually limb may turn into a wing
• Tendency toward perfection
• Organisms have tendency toward complexity
• Example Ancestors of birds had urge to fly---
• wings increased in size and became more suited
  to flying

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Lamarcks Theory

• Inheritance of acquired traits
• An organism that alters its physical traits can
  pass these traits on to offspring.

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Lamarcks Theory of Evolution
The pictures show selective use and disuse in the
evolution of the neck of the giraffe . . .
according to Lamarck.
The giraffe uses its neck to reach higher and
higher leaves, causing its neck to become longer.
This characteristic (long neck) is then passed
on to its offspring.
We know that this explanation is incorrect.
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Ideas that influenced DarwinThomas Malthus ---
1798

• Human population will grow faster than the
  space and food supplies needed to sustain it
• Malthus observed effects of war, famine, and
  disease on population

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Ideas that influenced DarwinAlfred Russel Wallace

• Work was largely unappreciated
• Field work in Amazon, East Indies, Malaysia, etc.
• Wrote Darwin with his theory of natural selection
• Darwins and Wallaces theories presented
  together in 1858

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Artificial Selection vs. Natural Selection

• Farmers breed individuals with desirable traits
  (selective breeding)
• Example broccoli, brussels sprouts, cauliflower,
  kale, kohlrabi derived from same ancestral plant
• In nature, organisms are selected for
  reproduction naturally (natural selection)

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Natural Selection

• Individuals best suited to their environment are
  most likely to survive and reproduce
• Over time, an organism becomes better suited to
  its environment (not so with artificial
  selection)
• Natural selection results in changes in inherited
  characteristics of a population

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Descent with modification

• Different species have developed through natural
  selection.
• Species have descended from ancestors, changing
  over time to occupy different niches
• This implies that all living organisms are
  related to one another
• All living things are descended from one common
  ancestor.

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Evidence of Evolution

• Fossil record
• Geographic distribution of living species
• Organisms with similar features can evolve
  separately if the environments are similar
• (see pg. 383 beaver, muskrat, capybara,
  coypu)
• Homologous body structures
• Similarities in early development

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Convergent Evolution

• Anteaters are found on four different continents
  not closely related
• Independently evolved long sticky tongue, few
  teeth, rugged stomach, large salivary glands

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Homologous Body Structures

• Different in mature form, but same embryonic
  tissues

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Homologous body structuresvestigial organs
A structure that has lost its functionality Exampl
e the presence of a hind limb in a whale
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Similarities in Early Development

• Similarity of embryos suggest these vertebrates
  had a common ancestor

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Stop Here

• End of Chapter 15

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Generic Bell Curve for Polygenic Trait
Section 16-1
Frequency of Phenotype
Phenotype (height)
Most traits are polygenic (controlled by two or
more genes)
example height
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Genetic Drift
Allele frequency in small populations changes due
to chance
Founder effect
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Section 16-2
Key
Directional Selection
Low mortality, high fitness
High mortality, low fitness
Food becomes scarce.
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Section 16-2
Stabilizing Selection
Key
Low mortality, high fitness
Selection against both extremes keep curve narrow
and in same place.
High mortality, low fitness
Percentage of Population
Birth Weight
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Section 16-2
Disruptive Selection
Largest and smallest seeds become more common.
Key
Population splits into two subgroups specializing
in different seeds.
Low mortality, high fitness
Number of Birdsin Population
Number of Birdsin Population
High mortality, low fitness
Beak Size
Beak Size
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Evolution vs. Genetic Equilibrium

• Evolution will not occur when allele frequencies
  remain constant----genetic equilibrium
• Hardy-Weinberg principle
• Allele frequencies in a population remain the
  same unless one or more factors cause the
  frequencies to change

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Hardy-Weinberg Principle

• Allele frequencies will remain the same as long
  as
• Random mating is occurring
• Population is very large
• No movement into or out of the population
• No mutations
• No natural selection
• Genetic equilibrium is maintained
• No evolution occurs

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Speciation formation of a new species

• Species--- a group of organisms that breed with
  each other and produce fertile offspring
• One species can evolve into 2 species
• Populations become reproductively isolated from
  one another
• Behavioral isolation (i.e., courtship rituals)
• Geographic isolation
• Temporal isolation (related to time)
• Results in populations with separate gene pools
• (2 new species)
• Review speciation in Darwins finches
  (pgs.408-409)