Evolution Chapter 16, 17, and 19 in textbook

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EvolutionChapter 16, 17, and 19 in textbook
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Darwins Theory of Evolution

• Evolution the process by which all living
  organisms have developed and diversified from
  earlier forms over time.
• Evolution is Just a Theory
• Scientific theory well-substantiated
  explanation of some aspect of the natural world
  that is confirmed through observation and
  experimentation
• A scientific theory can be supported or
  disproven, but never proven.
• Other scientific theories Cell Theory, Theory
  of Plate Tectonics, Collision Theory

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Darwins Theory of Evolution

• Darwin set sail on a voyage around the world and
  made many observations.
• Organism in similar environments around the world
  had similar characteristics
• Australia has different plants and animals than
  Africa
• Australia and Africa have similar grassland
  environments.
• The plants and animals in both grasslands have
  similar characteristics even though they are
  different.

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Darwins Theory of Evolution

• Species always seemed well-suited for their
  environment
• At the Galapagos the environment on each island
  is very different.
• The animals found on each island seemed to had
  changed to match the environment.
• What can you infer about the environments on Hood
  and Isabella island by observing the tortoises?

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Darwins Theory of Evolution

• Ancient organisms resemble modern organisms.
• Fossils preserved remains or traces of ancient
  organisms
• By studying fossils you can infer why the ancient
  organism no longer exist.
• What modern organism Australopithecus and
  Neanderthal resemble. Why did they go extinct?

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Ideas That Shaped Darwins Thinking

• Geology
• In Darwins time, most people believed the Earth
  was a few thousand years old.
• Geologists began to gather evidence that the
  continents have been forming for millions of
  years.
• How did this information help Darwin form his
  theory on evolution?

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Ideas That Shaped Darwins Thinking

• Selective Breeding
• How could a farmer use selective breeding to get
  cow with larger horns?
• In order for selective breeding to work you need
  natural variation.
• Natural Variation individual organisms of the
  same species can have different characteristics.

• Darwin called this process artificial Selection
• Artificial Selection nature provides the
  variation and humans select those they find
  useful.
• How did this information help Darwin form his
  theory of evolution? (Darwin did not know about
  heredity)

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Ideas That Shaped Darwins Thinking

• Population Growth
• Economist Thomas Malthus realized that the human
  population was growing.
• If the population continued to grow, we would run
  out of resources.
• Once we run out of resources many people would
  die.

• How did this information help Darwin develop his
  theory on evolution?

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Darwins Theory of Evolution

• Darwin proposed natural selection as the
  mechanism of evolution.
• Natural selection the process by which
  organisms with variations most suited to their
  environment survive and produce more offspring.
• 3 criteria for natural selection to occur
• Natural Variation
• Struggle for Existence
• Survival of the Fittest

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Darwins Theory of Evolution

• Natural Variation
• There must be diversity among the individuals of
  a population (the have different
  characteristics).
• The traits must be heritable
• Struggle for Existence
• Species must compete for limited resources and
  avoid predators.
• Fitness the organisms ability to survive and
  reproduce.

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Darwins Theory of Evolution

• Survival of the Fittest
• Only the most fit individuals will be able to
  survive and reproduce to pass on their
  adaptations.
• Adaptation any inherited characteristic that
  increases an organisms fitness (ability to
  survive and reproduce)
• Which insect has the highest fitness?

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Lamarcks Theory of Evolution

• Lamarck proposed a theory of evolution 50 years
  before Darwins theory.
• Lamarcks Two Ideas
• The inheritance of acquired traits.
• Lamarck thought that traits acquired during an
  organisms life could be passed on to the next
  generation.
• How would Lamarcks explain the evolution of a
  giraffes long neck?

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Lamarcks Theory of Evolution

• 2. Use and Disuse
• Lamarck thought that body parts that were not
  being used were gradually disappearing.

• How would Lamarck explain the evolution of a cave
  fishs lack of eyes?

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Patterns of Evolution

• Adaptive Radiation
• Adaptive Radiation When a single species
  evolves into several different species over time.
• All organisms share a common descent
• All living organism evolved from a single common
  ancestor that lived billions of years ago.
• Over time, that organism evolve in different ways
  to give to rise to all of the modern living
  organisms.
• Organisms are closely related if they share a
  recent common ancestor.

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Patterns of Evolution

• How long ago did human and chimpanzees share a
  common ancestor?
• What is the chimpanzees closest living relative?

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Patterns of Evolution

• How are new species formed during adaptive
  radiation?
• Speciation The formation of a new species
  through evolution.
• Populations must be reproductively isolated from
  each other
• Populations can be isolated by geography,
  behavior or time.

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Patterns of Evolution

• 2. Convergent Evolution
• Unrelated organisms evolve similar adaptations
  because they live in similar environments
• Sharks and dolphins do not share a recent common
  ancestor.
• They have similar characteristics because they
  share a similar environment.

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Patterns of Evolution

• 3. CoEvolution
• The evolution of two or more species, each
  adapting to changes in the other
• Occurs when species interact closely with each
  other.
• Ex Cheetah and Gazelles have co-evolve to
  become the fastest and 2nd fastest land animals

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Patterns of Evolution

• Punctuated Equilibrium
• Species do not evolve for long periods of time
  and then go through short period of rapid
  evolution.
• What causes the period of rapid evolution?
• Mass Extinctions A large number of species die
  out in a short time.

• Isolation A group of individual gets isolated
  from the main population.

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Patterns of Evolution

• Gradualism
• Organisms have evolve at a slow and steady rate.
• This theory is in contrast with punctuated
  equilibrium.

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Evidence of Evolution

• Homologous Body Structures
• Body structures shared by related species that
  have a similar structure but different functions.
• Supports the theory that organisms evolved from a
  common ancestor.

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Evidence of Evolution

• Analogous Body Structures
• Body parts in different species that is similar
  in function but not in structure
• Structures evolved in response to a similar
  environmental challenge.
• Supports convergent evolution

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Evidence of Evolution

• Embryology
• Closely related organisms look more similar in
  the early stages of embryonic development.
• Genetics
• All living things have the exact same genetic
  code.
• A group of 3 DNA nucleotides will code for the
  same amino acid in all organisms.
• Closely related organisms have a similar DNA
  sequence.

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Evidence of Evolution

• Geologic Time Scale a timeline of earths
  history.
• Major changes in fossils separate segments of
  time (periods).
• The end of each Era is usually a mass
  extinction.
• 99 of all species that ever lived on Earth are
  extinct

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Evidence of Evolution

• Scientists must determine the age of the fossil
  to determine where the organism fits in the
  geologic time scale.
• 2 Methods of Determining Age of Fossils

• Relative Dating
• Where is it in the rock layer?
• Deeper layer older fossil
• Cant tell you exactly how old the fossil is,
  just that it is older or newer than another fossil

Put the fossils in order from most modern to
oldest.
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Evidence of Evolution

• Radioactive Dating
• Calculate the age of the sample based on the
  amount of radioactive isotopes it contains.
• half life the time required for half of the
  radioactive isotopes to decay.
• Half life of carbon-14 is 5,715 years.

• How old is a fossil if 25 of the carbon 14 is
  remaining?

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Origin of Life

• How did life begin on Earth?
• Miller and Urey conducted an experiment to
  determine if organic molecules could be formed
  under the conditions of early Earth?
• They placed water in a flask and they added the
  gases that made up the atmosphere at that time.

• They boiled and electrocuted it many time.
• Eventually this process produced amino acids.

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Origin of Life

• The earliest forms of life had to be anaerobic.
  Why?
• Most living organisms need oxygen for cellular
  respiration.
• What is the main purpose of cellular respiration?
• Anaerobic organisms used fermentation produced
  energy without oxygen.
• Cyanobacteria the first organism to do
  photosynthesis.
• How did photosynthesis change the atmosphere?

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Origin of Life

• Endosymbiotic Theory The mitochondria and
  chloroplasts of eukaryotic cells were once
  independent prokaryotic cells.
• The prokaryotic cells were engulf by larger
  cells
• One engulfed cell became the mitochondria
• One engulfed cell became the chloroplast
• Evidence The mitochondria and chloroplasts have
  their own membranes and DNA.

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Evolution as Genetic Change

• Evolution, in genetic terms, is a change in the
  allele frequency a population over time.
• Gene Pool the combined genetic info. of all the
  members of a population
• Relative Frequency the number of times that an
  allele occurs in a gene pool compare to the total
  number of alleles

What is the allele frequency of the black and
brown alleles?
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Evolution as Genetic Change
Natural selection affects polygenic traits
differently than single gene traits.

• Single-Gene Trait
• Controlled by one gene that has two alleles
• Two distinct phenotypes
• Ex Tall or Short Pea Plants

• Polygenic Trait
• Controlled by more than one gene with many
  alleles
• Many possible genotypes and phenotypes
• Ex Human Height

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Evolution as Genetic Change

• Natural selection can affect the distributions of
  polygenic phenotypes in any of 3 ways

• 1. Directional Selection
• When individuals at one end of the curve have
  higher fitness than individuals in the middle or
  other end.
• Entire curve shifts
• Favors one of the extreme variations

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Evolution as Genetic Change

• Stabilizing Selection
• Individual in the center of the curve have higher
  fitness than those at the ends of the curve.
• Center remains stable but narrows entire graph
• Favors average individuals
• Ex weight of human infants

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Evolution as Genetic Change

• Disruptive Selection
• When individuals at each end of the curve have
  higher fitness than those in the middle
• Favors both extreme variations
• Creates two distinct phenotypes (can lead to
  speciation)

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Evolution as Genetic Change

• Genetic Drift random change in allele frequency
  of a small population due to chance.
• Does not increase the overall fitness of the
  population
• More likely to occur in small populations.

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Evolution as Genetic Change

• Hardy-Weinberg Principle
• A population will not evolve if the following
  conditions are met
• Random Mating
• Large Population
• No Migration
• No mutations
• No natural selection

• Genetic Equilibrium when the allele frequencies
  in a population remain constant over time.
• The population is not evolving

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Evolution as Genetic Change
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Lamarcks Theory of Evolution

• Evaluating Lamarcks Theory
• Lamarck was one of the first to recognize that
  life changes over time
• He also realized that organisms were adapt to
  their environment
• He didnt know how traits were inherited
  (acquired traits cannot be inherited)

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Coevolution
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Darwin vs. Lamarck
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Lamarck vs. Darwin