Evidence supporting theory of evolution

1
Evidence supporting theory of evolution

• Analogous structures
• Structures similar in form and function.
• Develop as a result of convergent evolution?

2
Evidence supporting theory of evolution

• Lifes chemistry
• Organisms are made of molecules and studying the
  molecules can help us understand possible
  relationships.
• Example Proteins
• Made of amino acids bonded together.
• Similar to a strand of pearls.
• More closely related two organisms are, the more
  closely their proteins resemble each other.

3
Speciation

• Speciation species giving rise to new species.
• Some segment of original population must be
  isolated from the rest.
• Reproductive isolation is an essential
  ingredient.
• Occurs via two mechanisms
• Allopatric Speciation
• Sympatric Speciation

4
Allopatric speciation

• Definition Speciation that occurs between
  isolated populations.
• Originated in different fatherlands.
• Must be geographically isolated.

5
Allopatric speciation

• To reach and colonize new area, must realize
  three opportunities
• Geographic
• Physiological
• Ecological

6
Sympatric speciation

• Definition Speciation among populations whose
  ranges overlap.
• Occur in same fatherland.
• Can occur with species occupying different
  habitats, but in the same range.

7

• Both types of speciation can be occurring at the
  same time.
• Initially population is geographically isolated.
• If geographic barrier is removed, populations
  overlap.
• Could still be isolated by differences in
  preferred habitat, courtship displays, breeding
  season, preferred.

8

• If not isolated by differences, then two
  populations will merge into one species.

9
Patterns in Evolution

• Convergent evolution
• Unrelated species living in similar environments
  and facing similar environmental challenges
  sometimes evolve similar characteristics.

10
Patterns in Evolution

• Divergent evolution
• Closely related species living in different
  environments and facing different environmental
  challenges sometimes evolve dissimilar
  characteristics.

11
Patterns in Evolution

• Adaptive radiation
• Sometimes, several species will evolve from a
  single, ancestral species.

12
Patterns in Evolution

• Coevolution
• Evolution of one species affects the evolution of
  another species.
• As predators evolve, prey evolves. As prey
  evolves, predators evolve.
• Example Cheetahs feed on Thompsons gazelles
• As the speed of one population of cheetahs
  improves so does the speed of the Thompsons
  gazelles .

13
Patterns in Evolution

• Gradualism
• Evolution may occur as a slow, gradual process of
  change.
• Theory favored by early evolutionists.

14
Patterns in Evolution

• Punctuated equilibrium
• Evolution may proceed with long periods of
  relatively little change (stasis) punctuated with
  short periods of intense change.
• Examples House flies, trilobites,
  antibiotic-resistant bacteria.

15
Evolution does not always occur

• Natural selection can only work on existing
  variation.
• Variation cannot be created on demand.
• Some species lack range of variation to support
  evolution.

16
Results of evolution

• Everywhere we look on the Earth, you can find
  organisms.
• Scientists have described 1.5 millions species
• Still many species yet to be described.
• Predictions indicate there may be 10-100 times as
  many species as those already described.

17
Darwins Theory Debated

• Three main criticisms
• Darwin lacked direct evidence for natural
  selection.
• Indirect evidence was unconvincing
• Darwin could not explain the source of variation
  in a population and inheritance of variation.
• Answered by an understanding of genetics
• What is the rate at which organisms evolve?
• Slow and continuous or jerky and discontinuous?

18
Darwin recognizes three special cases of natural
selection

• Sexual selection explained flamboyant appearance
  amongst birds.
• Sexual selection female birds choose mates and
  are attracted to males with extreme features.
• Females breed with them and extreme features
  passed to offspring.

19
Darwin recognizes three special cases of natural
selection

• Altruism
• Individual behavior benefits a social group often
  at the expense of the individual.
• Example worker bees in a hive
• Kin Selection
• Individuals help kin raise their young.