Evolution and Natural Selection

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Evolution and Natural Selection

• Miss Napolitano Mrs. Haas
• CP Biology

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What helps these organisms survive?
Poison Dart Frog
Snowshoe Hare
Eagle Owl
Anglerfish
Desert Tortoise
Australian Wolf Spider
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Adaptations help organisms survive!

• Adaptations inherited characteristics that
  increase an organisms chance of survival
• 3 types of adaptations
• Anatomical (structural)
• Ex quills on a porcupine
• Physiological (process)
• Ex Ability of a plant to photosynthesize
• Behavioral
• Ex hunting patterns in lions

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Lets start at the beginning...

• Evolution species change over time
• The Theory of Evolution explains how modern
  organisms have descended from ancient organisms
• Theory well-supported, testable explanation of
  phenomena

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Facts About Evolution

• It is a Scientific Theory (just like Gravity)
• A vast majority of scientists accept it
• It is supported by a large body of evidence
• There is no scientific evidence contradicting
  evolution

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Charles Darwin England

• Major contributions to our understanding of
• evolution
• Set sail on the H.M.S. Beagle in 1831 for a
  voyage around the world
• Gathered evidence that led him to propose an
  evolutionary hypothesis about how life changes
  over time

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Darwins Observations

• Saw lots of diversity and organisms that he did
  not see at home!
• Collected 68 different beetle species in one day
  in the Brazilian forests!
• Visited Argentina and Australia compared
  wildlife
• Both had similar grassland ecosystems
• Inhabited by very different animals
• Why were there no kangaroos in England?
• Collected remains of ancient organisms (fossils)
  compared them to current species

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The Galapagos Islands

• Located 1000 km west of South America
• Clumped together with very different climates
• Some hot, dry, barren
• Others had huge assortment of plants, animals,
  vegetation
• Darwin took interest in land tortoises marine
  iguanas
• Varied from one island to another
• Ex shape of tortoise shell
• Finches had different beaks in different locations

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Darwins Finches

• Darwin Were these finches once members of the
  same species? Did these finches evolve from an
  original common South American ancestor? Hmmm...

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Keep in mind...

• Darwin was revolutionary!
• In the 1800s, most people thought
• the Earth was only a few thousand years old (How
  old is it, again?)
• Species did not change over time
• Major geologic features were produced by
  catastrophic events that humans rarely witnessed

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Scientists Who Contributed to Darwins Theory of
Evolution

• James Hutton Charles Lyell
• Earth is millions (not thousands) of years old
• Processes that changed Earth in the past are the
  same processes that operate in the present
• Thomas Malthus
• Continuous reproduction will lead to less food
  living spaces
• Jean-Baptiste Lamarck
• By selective use of organs, organisms gain or
  lose traits during their lifetime. The traits can
  then be passed town to offspring
• Invalid! Behavior does not affect heritable
  characteristics

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Darwin Origin of Species

• Origin of Species Darwins published work (1859)
• Introduced the term natural selection
• Presented evidence that evolution has been taking
  place for millions of years
• Controversial!

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Variations Artificial Selection

• Remember During Darwins time, not much was
  known about genetics!
• Darwin noted natural variations in traits
• Artificial selection farmers/breeders mate
  plants or animals with desirable genetic traits
  to produce offspring with desired traits
• Examples of artificial selection
• Dog breeding
• Horse breeding

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Darwins Observations

• Darwin found fossils of extinct species
• Plants animals of Galapagos islands are similar
  to those in Ecuador
• Conclusion species migrated from South America
  to islands changed after they arrived
• Called this descent with modification

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Isolation Evolution

• Members of the original species migrated to
  different areas.
• Different areas have different resources.
• Different beaks are more beneficial depending on
  the available resources

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Variation Among Tortoises
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Darwins Theory of Evolution by Natural Selection
(1844)

• Natural Selection individuals that possess
  superior traits are more likely to survive,
  reproduce, pass the favorable traits to the
  offspring
• Adaptation the changing of a species in response
  to its environment

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Survival of the Fittest

• Coined by Herbert Spencer, not Darwin
• Replaced the term natural selection in 5th
  edition of Origin of Species
• Fittest does not always mean strongest!
• Fittest able to successfully survive reproduce

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Evolution Controversy

• Severely criticized by church government
• Alfred Wallace working on the same theory (1858)
• Darwin could have published his works early, but
  thought it would be too controversial. He only
  published once Wallace developed his ideas on his
  own
• People outraged with the idea of being related to
  apes

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Evidence of Evolution

1. Fossil Evidence
2. Anatomical Evidence
3. Biochemical Evidence
4. Embryonic Evidence

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Fossil Evidence

• Missing links may be found in the fossil record
• Ex 1990s fossils linked whales to mammals

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Anatomical Evidence

• Homologous structures similar structures,
  different functions
• Ex human arm, cat forelimb, whale flipper, bat
  wing

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Anatomical Evidence

• Analogous structures different structures,
  similar functions
• Ex butterfly wings bird wings

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Anatomical Evidence

• Vestigial structures structures that are present
  but reduced in size or nonfunctional as compared
  to related organisms
• Ex appendix, ear muscles, wings on flightless
  birds (penguins), whale pelvis

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Biochemical Evidence

• Species characteristics change as a result of
  changes in DNA
• Caused by random mutations
• The more similar the species, the more similar
  their DNA sequences

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Embryonic Evidence

• Vertebrate embryos develop similarly
• Development evolved as new genetic instructions
  were layered on top of older ones
• Ex tails, limb buds, pharyngeal pouches

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Patterns of Evolution

• Gradualism change generally occurs over long
  periods of time
• Punctuated equilibrium periods of little/no
  change interrupted by periods of rapid change
• Fossil record provides evidence for both!
• Gaps in fossil record
• Sudden disappearance of some organisms
• Some organisms unchanged for long periods of time
• Some organisms changed gradually

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Gradualism vs. Punctuated Equilibrium
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Phylogenetic Tree

• Phylogenetic Tree shows how organisms are
  related through evolution
• Forks in the tree represent common ancestors

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Update 2 Types of Evolution

• Microevolution change within a species over time
• Causes the frequency of certain genes within a
  population to change over time
• Macroevolution change creating a new species
  over time
• Isolation 2 populations of the same species are
  separated
• 2 different populations evolve in different
  directions due to resource availability
• When individuals of both populations cannot
  interbreed, they are considered to be two
  different species
• Species that are better suited to new conditions
  may replace others, causing extinction (permanent
  disappearance of a species)

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Examples of Microevolution

• Industrial Melanism the darkening of populations
  over time in response to pollution
• European peppered moth Biston betularia
• Dark variety rare until 1850, more dark by 1950
• Sickle Cell Anemia
• Harmful in western countries, but advantageous in
  Africa since individuals with sickle cell anemia
  resist malaria
• Antibiotic Resistance

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Antibiotic Resistance

• Antibiotics kill bacteria with low resistance
• Only the bacteria with high resistance survive,
  they reproduce
• Soon, all bacteria have high resistance,
  antibiotics no longer work to kill the bacteria
  population
• What does this mean?
• Bacteria have evolved to become more resistant
  through natural selection
• In other words, the ones more equipped to survive
  the antibiotic treatment were able to reproduce
  successfully

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Antibiotic Resistance
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Patterns of Microevolution

• Directional selection selects for one extreme
  trait
• Where malaria is not present, sickle cell anemia
  is selected against
• Balancing (stabilizing) selection selects for
  intermediate traits
• Birth weight too small is too weak, too large
  means complications during birth, therefore,
  intermediate is best
• Disruptive selection both extremes are selected
  for
• Shell color light shells blend with sand, dark
  shells blend with rocks

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Patterns of Microevolution
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Microevolution Leads to Macroevolution

• As changes accumulate over time, living species
  may become different from ancestors from other
  species
• Biologists changes within a species eventually
  lead to appearance of a new species
• Speciation process by which new species form