Theories of Evolution

1
Theories of Evolution

• Evolution slow, gradual change over time.
• Geologic evolution changes in the non-living
  planet over time.
• Biological evolution changes in living
  organisms over time.

2
Jean Baptiste LaMarck 1809

• Early Theory of Evolution
• (gradual changes in species over time)
• Use and Disuse He hypothesized that organisms
  were able to develop new structures as they
  needed them and they were able to pass them on to
  their offspring. This was called the..
• Theory of Inheritance of Acquired Traits
• Got evolution right, but got mechanism wrong !!
• Inherited Traits characteristics genetically
  passed on the offspring.
• Acquired Characteristics a trait that develops
  during an individuals lifetime.

3
Charles Darwin

• 1809-1882
• Ships naturalist aboard the HMS Beagle collected
  hundreds of specimens and made extremely detailed
  observations of the natural world on the 5 year
  scientific expedition. Upon his return and
  further study of geology and natural population
  increase, he developed his
• Theory of Natural Selection
• Wrote (1845) his famous book
• On the Origin of Species

4
(No Transcript)
5
Darwins Theory of Natural Selection

• 1 Overproduction
• Organisms tend to have many more than two
  offspring so at least some will survive (yet
  populations usually do not grow rapidly in the
  wild)

6

• 2 Competition - Therefore they
• must compete for resources
• (food, space, mates)

7
Natural Selection

• 3 Variation - variation within the population.
• 4 Adaptation - Therefore some of them must be
  better adapted to their environment

8

• 5. Natural Selection- the ability of
  organisms that are best adapted to survive and
  reproduce . Those that are less well adapted will
  not survive.

9
Speciation

• Eventually, over generations and time, new
  species will evolve from older forms by natural
  selection of better adapted forms.

10
Fitness

• Which is more fit???

11
Evidence for EvolutionAll of the fields of Life
Science show evidence of evolution.

• A. The Fossil Record
• Fossil the remains or evidence of past life
  recorded in rock.
• (molds, impressions, bones, shells, teeth,
  preserved in ice, etc.)
• 1. Fossils are found most often sedimentary rock.
• 2. Relative age can be determined by the fossils
  position in the layers. The oldest fossils are
  found below the younger ones.
• 3. Absolute dating uses the principal of
  radioactive dating
• The half-life of known radioactive compounds
  never changes.
• (ex. Carbon 14 found in bones and shells can
  determine their actual age in years).
• Ex. Fossil remains clearly show the gradual
  evolution of the modern horse.

12
Fossil Record
13
B. Comparison of Similar Anatomy or Structures

• 1. Homologous structures - those that appear to
  have come from a common ancestor. These indicate
  that species are related.
• Ex. Bats wing, human arm and whale flipper bones.
• 2. Analogous structures - those that are used
  for the same function but are not similar. These
  indicate species are not related.
• 3. Vestigial structures those that no longer
  serve a useful function
• Ex. Human appendix, tailbone (coccyx)

14
Bones of the Mammalian Forelimb
15
Comparative Anatomy
16
Comparative Embryology

• Comparative Embryology examination of
  differences and similarities in embryo
  development (before birth).
• ex. Comparison of bird, fish and early human
  embryos

17
E. Behavior Comparisons
18
F.

• Biochemical Comparisons
• Recent developments (Human Genome Project) have
  allowed for the comparison of DNA from different
  species and groups within species. This new
  evidence is the strongest yet that consistently
  supports accepted evolutionary theory.
• DNA - our DNA and that of a Chimpanzee is more
  than 99 identical. Gorillas and Baboons have
  somewhat less (95-97) and mice have 80
  identical DNA.
• Protein and Enzymes
• Ex. Cytochrome C, a respiratory enzyme common to
  all animals is slightly different in different
  species. Humans differ from monkeys by one amino
  acid in their cyt C. We differ from pigs by 10
  amino acids. Chicken cyt C has 13 different
  amino acids and fish differ by 21. This clearly
  shows the accepted evolutionary relationship
  between vertebrates.

19
Molecular Comparisons
20
Sources of Variation

• A. Mutation
• A mutation is a change in the DNA of an organism
  due to external or internal factors. (toxins,
  radiation, random,etc.)
• Most mutations are NOT beneficial to the
  organism.
• Some may become beneficial if the environment
  changes, provided they do not harm the
  individual. (ex. Giraffes neck)

21
Genetic Recombination

• Sexual reproduction leads to new combinations of
  genes.
• Ex. You are not exactly like either one of your
  parents.

22

• C. Speciation
• New species will arise more quickly if they are
  geographically isolated. Natural barriers such
  as mountains, deserts, rivers or landslides can
  separate members of a population. If they can no
  longer interbreed they may change enough by
  natural selection to become a separate species.
• (ex. Darwins finches)
• The loss of the ability to interbreed is called
  reproductive isolation. Sometimes this is caused
  by changes in reproductive organs such that the
  offspring will not survive.
• Sometimes this type of isolation is caused by
  changes in courtship behavior or the timing of
  mating cycles.

23
Speciation

• Geographic isolation of populations
• Can lead to
• Reproductive isolation of population
• Can lead to
• New Species
• (unable to breed when together)

24
Geographic Isolation

• Members of a population may become isolated from
  one another by geographic boundaries like
  mountains, rivers or even oceans

25
Reproductive Isolation
26
New Species Evolve
27
V. Evolutionary Time Frames

• Gradualism species descend from a common
  ancestor gradually as the change in minor ways
  over a long period of time.
• B. Punctuated Equilibrium a newer theory
  developed by Stephen Jay Gould states that
  species remain fairly constant over long periods
  of time until a great change in their environment
  cause relatively rapid speciation.

28
Gradualism

• Seen often in the fossil record of marine
  invertebrates like snails.

29
Punctuated Equilibrium

• Seen in the evolution of birds from dinosaurs

30
Gradualism
31
Convergent Evolution
32
Divergent Evolution(Adaptive Radiation)
33

• Evolution is a fact species do change over
  time!!
• Natural Selection is a scientifically supported
  theory that explains this fact.
• Decades of experimental and observational
  evidence support Darwins theory of
• Evolution by Natural Selection