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Evolution by Natural Selection

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Charles Darwin. Father of Evolutionary Theory. H.M.S. Beagle. Theory of Natural Selection. Explains how evolution works – PowerPoint PPT presentation

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Title: Evolution by Natural Selection


1
Evolution by Natural Selection
  • Adapter from Mrs. Knox

2
Charles Darwin
  • Father of Evolutionary Theory
  • H.M.S. Beagles Naturalist
  • Studied anatomy of
  • biological specimens
  • formulated the Theory of Natural Selection.

3
Survival of the Fittest
  • Natural Selection individuals best suited to
    their environment
  • survive better
  • reproduce better
  • pass on their genes better
  • Depends on variation existing in populations.
  • Variation differences in appearance within the
    same species.
  • examples hair color, feather color beak size
  • Nature selects for favorable traits and against
    those without them.

4
Normal Curve
  • Natural variation in populations is the raw
    material for evolution
  • Natural variation comes from genes

5
Adaptations
  • Adaptations a trait which helps a species
    survive.
  • Adaptations may take millions of years or may
    occur rapidly.

6
  • Peppered moth populations have evolved to a
    darker form
  • trees become darker because of pollution
  • dark moths in existence gained camouflage
  • Survived better reproduced better than light
    moths

7
Types of Adaptations
  • Structural
  • Changes in a body
  • Mimicry camouflage
  • Physiological
  • Changes in metabolic processes
  • Pesticide resistance in insects
  • Behavioral
  • Changes in behavior
  • Social behavior in wolves or primates

8
3 Types of Natural Selection
  • Stabilizing Selection selects for average
    individuals and against extremes
  • Large spiders are easily seen captured
  • Small spiders cant catch enough prey
  • Medium spiders dont attract predators are
    large enough to be effective predators

9
3 Types of Natural Selection
  • Directional Selection selects for one extreme.
  • Deep burrowing insects invade woodpecker habitat
  • Those woodpeckers with longer beaks eat better,
    survive better reproduce better

10
3 Types of Natural Selection
  • Disruptive Selection both extremes are selected
    for.
  • Rocks in flounder environment are both light and
    dark
  • White and brown flounder can blend in but tan
    flounder cant
  • Tan flounder are selected against

11
Speciation
  • Natural Selection leads to the development of new
    species
  • Species group of organisms that look alike and
    have the ability to
  • interbreed
  • have fertile offspring

12
Cause of Speciation
  • Geographic Isolation physical barrier separates
    population into 2 parts.
  • Breeding between 2 populations stops
  • Over many generations populations change into new
    species
  • Examples clear cutting, sea levels changes,
    volcanic eruptions

13
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14
Causes of Speciation
  • Reproductive Isolation formerly interbreeding
    populations are prevented from creating fertile
    offspring
  • Example fall and spring breeding seasons

15
Speed of Speciation
  • Gradualism speciation occurs at slow steady rate
    with small adaptive changes gradually accumulate
  • Punctuated Equilibrium speciation occurs in
    rapid bursts with long periods of stability in
    between.
  • environmental conditions change
  • introduction of new competitive species

16
Patterns of Evolution
  • Adaptive Radiation ancestral species separate
    into many species which occupy different niches.

17
Patterns of Evolution
  • Divergent evolution species have become more and
    more different.
  • Homologous structures same structure from common
    ancestor, different function

18
Patterns of Evolution
  • Convergent Evolution distantly related organisms
    evolve same traits.
  • Analogous structures different structure, same
    function.
  • fins streamline body for aquatic predators

19
Evidence for Evolution
  • Fossils evidence in sedimentary rock of an
    organism that lived long ago.
  • Amber
  • Casts
  • trace fossils
  • Imprints
  • Molds
  • petrified wood

20
How do we find the age of a fossil?
  • Relative dating layers of rock closer to the
    surface are younger than deeper rock, so
    placement of the fossil in those layers gives an
    estimate of its age.

21
How do we find the age of a fossil?
  • Radiometric dating using the amount of
    radioactive isotopes left in the fossil to
    estimate its age.
  • Half-life the amount of time it takes for half
    of a specific radioactive isotope to decay.
  • Potassium 40 turns into
  • Argon 40 over time
  • 1/2 life 1.3 billion years
  • Carbon-14 5730 years

22
  • C-14 Dating Procedure

23
Evidence for Evolution
  • Comparative Anatomy comparing body parts of
    species.
  • homologous analogous structures

24
Evidence for Evolution
  • Comparative Embryology if embryos appear similar
    then there is a common ancestor.

25
Evidence for Evolution
  • Vestigial structures body part that is reduced
    in function today, but may have been used by
    ancestors.

26
Evidence for Evolution
  • Genetic Comparisons DNA testing to see how many
    pairs of nucleic acids are similar.
  • Most reliable form of evidence.
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