Evolution and Darwin

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EvolutionandDarwin
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What is evolution?
X

• A slow change over time

• The development of new types of organisms from
  preexisting types of organisms over time

• A heritable change in the characteristics within
  a population from one generation to the next

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Evolution Primers

• Isn't Evolution Just a Theory???

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History of Evolution
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Charles Darwin a brief history

• Born in England on February 12, 1809
• In 1831 began a 5-year journey on the HMS Beagle
  as a naturalist
• Observations and specimen collections led him to
  develop the single best idea anyone has ever
  had
• Developed a scientific theory of biological
  evolution that explains how modern organisms
  evolved over long periods of time through descent
  from common ancestors
• Darwin video clip

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• Darwin set sail on the H.M.S. Beagle (1831-1836)
  to survey the south seas (mainly South America
  and the Galapagos Islands) to collect plants and
  animals.
• On the Galapagos Islands, Darwin observed species
  that lived no where else in the world.
• These observations led Darwin to write a book.

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Darwins Observations

• 1.Species vary globally Darwin noticed that
  different, yet ecologically similar, animal
  species inhabited separated, but ecologically
  similar habitats around the globe
• Flightless birds (emu, ostrich, rhea)
• Convergent evolution

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Darwins Observations

• 2. Species vary locally Darwin noticed that
  different, yet related, animal species often
  occupied different habitats within a local area
• Tortoise, mockingbirds

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Darwins Observations

• 3. Species vary over time Darwin noticed that
  some fossils of extinct animals were similar to
  living species
• - fossils preserved remains of ancient,
  extinct organisms
• Who is Charles Darwin?

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Friends

• Friends Evolution Montage

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Ideas that Shaped Darwins Thinking

• Lyell Hutton
• Concluded that Earth is extremely old and that
  the processes that changed Earth in the past are
  the same processes that operate in the present
  (still changing)
• Hutton (in 1785) geological processes shape
  Earth
• Lyell (in 1830) uniformitarianism geological
  processes we see in action today must be the same
  ones that shaped Earth millions of years ago
• Lamarck 1809
• Inheritance of Acquired Characteristics ?
• Organism could change during their lifetimes by
  selectively using or not using various parts of
  their bodies then pass these acquired traits on
  to their offspring, enabling species to change
  over time ?
• One of the first naturalist to suggest that
  species are not fixed ?
• One of the first to try and explain evolution
  scientifically using natural processes ?
• Recognized that there is a link between an
  organisms environment and its body structures ?

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The Inheritance of Acquired CharacteristicsLama
rck vs Darwin

• Example
• -A giraffe acquired its long neck because its
  ancestor stretched higher and higher into the
  trees to reach leaves, and that the animals
  increasingly lengthened neck was passed on to its
  offspring.
• -A muscle builder will pass the muscles on to
  his offspring. NOT TRUE

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Ideas that Shaped Darwins Thinking

• Malthus 1798
• English economist
• Reasoned that if the human population grew
  unchecked, there would not be enough living space
  and food for everyone
• Artificial Selection
• Nature provides variations, but humans select
  those they find useful

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Artificial Selection

• The selective breeding of domesticated plants and
  animals by man.
• Question
• Whats the ancestor of the domesticated dog?
• Answer WOLF
• This is STELLA!!!!!

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Darwins Contribution to Science

• Darwin developed a scientific theory of
  biological evolution that explains how modern
  organisms evolved over long periods of time
  through descent of common ancestors.

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Darwin and Wallace

• Same conclusion about evolution as a result of
  similar experiences
• Influenced by Lyell and Malthus
• Observed plant and animal life in several parts
  of the world
• Wallace (1858) sent Darwin a manuscript
  describing natural selection
• Wallace and Darwin arrived at the theory of
  Natural Selection independently, and presented
  their ideas in public together in 1858

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Charles DarwinWallace kind of gets dissed

• Wrote in 1859 (11/24 pub)
• On the Origin of Species by Means of Natural
  Selection
• Main points
• 1. Struggle for Existence (competition)
• 2. Variation and Adaptation
• 3. Survival of the Fittest
• 4. Natural Selection

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Struggle for Existence

• Organisms produce more offspring than can
  survive. (OVERPRODUCTION)
• Grasshoppers can lay more than 200 eggs at a
  time. Only a small fraction of these offspring
  survive to reproduce.

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Variations and Adaptations

• There is variation in nature, and certain
  variations called adaptations increase an
  individuals chance of surviving and reproducing.
  
• Physical, physiological, and/or behavioral traits
  that enhance an organisms chances for surviving
  in its environment
• Green vs. yellow color in grasshoppers is a
  heritable variation green can blend into
  environment and avoid predators

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Survival of the Fittest

• Suggests that natural selection selects mainly
  for survival IT DOES NOT
• Selects for contribution of genes to future
  generations
• Reproduction resulting in viable offspring
• Selects for individuals that are able to produce
  the greatest number of offspring, that in turn,
  can survive and reproduce
• Green grasshoppers have higher fitness and so
  survive and reproduce more often than yellow

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Natural Selection

• How Does Evolution Really Work?

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Survival of the Sneakiest

• Survival of the Sneakiest

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• Will the grey mouse or white mouse survive more
  easily?
• Why?
• What characteristic is affecting the fitness of
  the mice?

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• Peppered MothsIn the year 1848, 5 of the
  population was dark colored moths while 95 was
  light colored.
• In the year 1895, 98 was dark colored while 2
  was light colored.
• In the year 1995, 19 was dark colored while 81
  was light colored.
• What was the reason for the changes in the number
  of dark and light colored moths?
• In the early 1800s, England was not so
  industrialized yet and pollution was still low.
  The trees had light colored bark so the light
  colored moths had a better advantage and a better
  survival rate than dark colored ones.
• In the late 1800s, England started to become more
  industrialized and factories increases. These
  factories caused trees to become soot coated, the
  bark was darker. The dark colored moths were then
  camouflaged and survived more than light colored
  ones.
• Then in the mid 1900s, the air started to become
  cleaner due to clean air laws. Trees began to
  have light colored barks and once again light
  colored moths increased in the population.

Year Dark Light
1848 5 95
1895 98 2
1995 19 81
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Another example of natural selection

• http//www.sciencenetlinks.com/interactives/evolut
  ion.html

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Darwins Finches

• A Close Look at Darwins Finches
• When Charles Darwin traveled to the Galápagos
  Islands, he found a variety of species of
  finches. Although each species was slightly
  different from the others, all the species were
  related. None of the finch species he found were
  similar to finches on the mainland.
• When Darwin saw such extensive diversity of
  species in a single group of birds, he
  hypothesized that they all could have descended
  from a common ancestor. His observations of these
  finches helped him formulate his concept of
  evolution.
• The phylogenetic tree below shows the
  relationships Darwin proposed among the species
  of finches. The tree is based on a comparison of
  the anatomy, behavior, and location on the island
  of each finch species. Look carefully at each
  species, and notice the dramatic difference among
  the beaks. Each type of finch has a beak adapted
  to its diet.
• Darwins finches are an example of adaptive
  radiation. Adaptive radiation is the emergence of
  many species from a common ancestor that was
  introduced to various new environments. For
  adaptive radiation to occur, the new environments
  must offer new opportunities and pose new
  problems of survival for the species.

1. Which of the ground finches illustrated above
   would be able to eat the largest, toughest nuts
   and seeds? Explain your answer.
2. Study the insect-eating finches shown in the
   diagram. What can you infer about the insects of
   the Galápagos Islands?

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What does Darwins mechanism for evolution
suggest about living and extinct species???

• All organism descended from a common ancestor
• Descent with modification
• Homer Evolution

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Evidence for Evolution

• Biogeography
• Fossil Record
• Comparative Anatomy
• Developmental Biology
• Comparative Biochemistry
• How Do We Know Evolution Happens?

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Biogeography study of where organisms live now
and where they and their ancestors lived in the
past

• Patterns in the distribution of living and fossil
  species tell us how modern organisms evolved from
  their ancestors
• Closely related species differentiate in slightly
  different climates
• Very distantly related species develop
  similarities in similar environments
• Adaptive Radiation
• Evolutionary process that gives rise to new
  species adapted to new habitats and ways of life

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The Age of the Earth and Fossils

• The Age of the Earth
• Earth had to be old enough for these proposed
  changes to occur plenty of time for Natural
  Selection
• Earth is 4.5 byo (determined by radioactive
  dating) plenty of time for natural selection to
  take place
• Fossils discovered after Darwin fill in some of
  the gaps in the fossil record
• One fossil shows the evolution of whales from a
  land-based mammal (book figure 16-3)

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Comparing Anatomy and Embryology

• Homologous Structures
• Parts that are similar in structure but different
  in function
• Humans, penguins, alligators, bats all have the
  same bones in their arms but they are used for
  different things
• Similar Embryos
• Embryos of different organisms are very similar
  and have similar structures early on
• Must have similar proteins at work
• Vestigial Structures
• Structures that are so reduced in size or
  function that they are merely traces of similar
  organs in other species (I.e. tailbone and
  appendix in humans)

• Analogous Structures
• Parts that are similar in function but not
  structure
• i.e. Wing of bee, bird, bat

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Genetics and Molecular Biology

• All organisms have DNA
• Therefore similar RNA, similar genes, and similar
  proteins
• All organisms have ATP

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Evolution of Populations Ch 17

• Process of change over time
• A change in the genes!!!!!!!!

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Population Genetics

• The science of genetic change in population.
• Population all the members of a species that
  occupy a particular area at the same time
• Gene Pool all the genes in all the members of a
  population

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Genes and Variation

• Genetics Joins Evolutionary Theory
• Variation is the raw material for natural
  selection
• Gene pool consists of all the genes, including
  all the different alleles for each gene, that are
  present in a population
• Relative frequency the number of times that the
  allele occurs in a gene pool, compared with the
  number of times other alleles for the same gene
  occur
• Therefore evolution is any change in the
  relative frequency of alleles in the gene pool of
  a population over time
• 3 Sources of Genetic Variation
• Mutations
• Genetic Recombination in Sexual Reproduction (Ind
  assortment and crossing over)
• Lateral Gene Transfer (conjugation)
• Single-Gene (2 pheno) vs. Polygenic Traits (many
  pheno/bell curve)
• Natural Selection acts directly on PHENOTYPES
  not actual alleles some phenotypes are better
  suited to an environment than others and they
  will survive, reproduce and pass on their genes.

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Evolution as Genetic Change in Populations
How Natural Selection Works 3 Types

• Stabilizing Selection
• Individuals with the average form of a trait have
  the highest fitness
• Represents the optimum for most traits
• Results in a similar morphology between most
  members of the species

• Directional Selection
• Individuals that display a more extreme form of a
  trait have greater fitness than individuals with
  an average form of the trait
• A shift in one direction
• Peppered moth

• Disruptive Selection
• Individuals with either extreme variation of a
  trait have greater fitness than individuals with
  the average form of the trait
• A shift in both direction, away from the center
• Shell color (dark rocks and light sand)

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Genetic Drift

• Random changes in the frequency of a gene in the
  absence of natural selection ? occurs because of
  CHANCE
• Occurs efficiently in small populations because
  small changes affect more members
• Two examples
• a. Bottleneck effect
• b. Founder effect

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Genetic Drift
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a. Bottleneck Effect

• Genetic drift (reduction of alleles in a
  population) resulting from a disaster that
  drastically reduces population size.
• Examples
• 1. Earthquakes
• 2. Volcanos

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b. Founder Effect

• Genetic drift resulting from the colonization of
  a new location by a small number of individuals.
• Results in random change of the gene pool.
• Example
• 1. Islands
• (first Darwin finch)

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Hardy-Weinberg Principle

• Genetic Equilibrium situation in which allele
  frequencies in the gene pool of a population
  remain constant
• The concept that the shuffling of genes that
  occurs during sexual reproduction, by itself,
  cannot change the overall genetic makeup of a
  population.
• Shows mathematically and theoretically that there
  are situations where evolution DOES NOT OCCUR
• Seldom achieved in nature

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Hardy-Weinberg Principle

• This principle will be maintained in nature only
  if ALL five of the following conditions are met
• 1. Very large population
• 2. Isolation from other populations (no
  immigration, no emigration)
• 3. No net mutations
• 4. Random mating
• 5. No natural selection
• Hardy-Weinberg Principle

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Species

• A group of populations whose individuals have the
  potential to interbreed and produce viable
  offspring.

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Speciation

• The evolution of new species. Species that
  occupy an otherwise unoccupied niche face no
  competition, they will therefore have a 100
  success rate

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Reproductive Isolation

• Any mechanism that impedes two species from
  producing fertile and/or viable hybrid offspring
  -factor necessary for the formation of a new
  species.
• Barriers
• 1. Geographic (rivers, mountains)
• 2. Behavorial - differences in courtship
  behavior
• 3. Temporal - fertile periods (time)

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Interpretations of Speciation

• Two theories
• 1. Gradualist Model (Neo-Darwinian)
• Slow changes in species overtime.
• 2. Punctuated Equilibrium
• Evolution occurs in spurts of relatively rapid
  change.

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Macroevolution

• The origin of taxonomic groups higher than the
  species level.

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Adaptive Radiationaka Divergent Evolution

• Emergence of numerous species from a common
  ancestor introduced to new and diverse
  environments.
• Example
• Darwins Finches

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Darwins Finches an example of Adaptive Radiation
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Convergent Evolution

• Species from different evolutionary branches may
  come to resemble one another if they live in very
  similar environments.
• Example
• 1. Ostrich (Africa) and Emu (Australia).
• 2. Sidewinder (Mojave Desert) and
• Horned Viper (Middle East Desert)
• 3. Shark and Dolphin

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Coevolution

• Evolutionary change, in which one species act as
  a selective force on a second species, inducing
  adaptations that in turn act as selective force
  on the first species.
• Example
• 1. Acacia ants and acacia trees
• 2. Humming birds and plants with flowers with
  long tubes

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The Age of the Earth and Fossils

• Fossils
• Trace the evolution of modern species from
  ancient/extinct ancestors
• Relative dating vs.
• Absolute dating

• Radiometric Dating
• When unstable nuclei release particles or radiant
  energy until the nuclei becomes stable
• Half-life The length of time it takes for
  one-half of a sample to decay to stable form

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The Earth is born
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Date Event Additional Info
4.6 bya Earth was born
4 bya Cooling of Earth, 1st solid rocks formed on earths surface
4-3.8 bya Volcanic activity meteorites release gases that produce earths atmosphere Contained H2O vapor, CO, CO2, H2, N2, NH3, CH4 It did NOT contain oxygen
3.8 bya Cooling continues, water appears, beginning of oceans Earth cool enough for liquid to stay on the ground
3.5 bya Age of first prokaryotic microfossils Heterotrophic obtained nutrients from organic soup Anaerobic able to live in oxygen-free environment
3.4 bya Appearance of 1st autotrophs Organic soup begins to run out Photosynthesis begins using H2S instead of water
2.2 bya Introduction of oxygen into the atmosphere More modern form of photosynthesis appeared Used H2O instead of H2S Caused earth to cool as they converted CO2 ? O2 Led to aerobic respiration Ozone layer protection
1.6-1.1 bya 1st eukaryotic cells evolved Sexual reproduction evolved Multicellular organisms arose Nucleus contains DNA, have membrane bound organelles, etc. Increased the speed of evolution Increased genetic variation
1700s Spontaneous Generation (abiogenesis) idea that life comes from non-life Disproven through Redi, Spallanzani, Pastuer
1953 Miller Urey mix methane, water, ammonia, and hydrogen with energy (sun lightning) Primordial Soup Amino acids other organic compounds are produced as by-products Provide glimpse at how molecules (proteins) may 1st have formed on the Earth
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The Age of the Earth and Fossils

• The Age of the Earth
• Earth had to be old enough for these proposed
  changes to occur
• Earth is 4.5 byo (determined by radioactive
  dating)

• History of Earth (24hours)
• 1200am Earth is formed
• 500am Prokaryotes appear
• 400pm Eukaryotes appear
• 1000pm Invasion of land
• 115930pm Humans appear

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Miller/Urey Experiment and Primordial Soup

• Oparin and Haldane hypothesized that the early
  atmosphere was composed of ammonia (NH3),
  hydrogen gas (H2), water vapor (H20), and
  compounds made of carbon and hydrogen, like
  methane (CH4). They thought that at high
  temperatures, simple organic compounds (like
  amino acids) could form. When earth cooled, and
  lakes and oceans formed, theses simple compounds
  could be found in the water and enter complex
  chemical reactions fueled by lightning and
  ultraviolet violet radiation resulting in
  macromolecules essential to life like proteins.
• Miller and Urey 1953 set up an apparatus to test
  Oparins hypotheses. Their experiment produced a
  variety of organic compounds, including amino
  acids

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EndosymbioticTheory

• What is the theory of endosymbiosis? Theory that
  large prokaryotic, unicellular organisms engulfed
  (ate) smaller prokaryotic, unicellular organisms.
  Engulfed prokaryotes eventually gave rise to
  modern mitochondria and chloroplasts.
• What evidence supports the hypothesis that
  mitochondria and chloroplasts were once free
  living prokaryotic cells? Replicate
  independently and replicate like prokaryotes
  (binary fission), have their own DNA and their
  own ribosomes (also similar to DNA and ribosomes
  of prokaryotes)

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