CHAPTER 15 NOTES

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CHAPTER 15 NOTES
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EVOLUTION

• Evolution change over time
• Evolution is a theory (a well- supported,
  testable explanation of phenomena that have
  occurred in the natural world)

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CHARLES DARWIN

• Contributed more to our understanding of
  evolution than anyone
• Journeyed around the world on the HMS Beagle and
  made observations and collected evidence
• Collected fossils (preserved remains of ancient
  organisms)
• The islands that influenced Darwin the most were
  the Galapagos Islands (a group of islands with
  very different environments)

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Other Scientists that influenced Darwin

• 1. Hutton Lyell studied geological change to
  show that the Earth changes over time
• 2. Lamarck was the first scientist to recognize
  that living things change over time
• 3. Malthus reasoned that if the human population
  continued to grow unchecked, sooner or later
  there would be insufficient living space and food
  for everyone (war, famine and disease help keep
  this growth in check)

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Lamarcks ideas

• 1. Organisms constantly strive to improve
  themselves
• 2. Most-used body structures develop, but unused
  ones waste away
• 3. Once a structure is modified by use or disuse,
  the modification is inherited by the organisms
  offspring (inheritance of acquired
  characteristics)
• ALL OF THESE WERE PROVEN WRONG, but Lamarck paved
  the way for the work of later biologists.

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CHARLES DARWIN

• In 1859, Darwin published the results of his
  work in a book On the Origin of Species in
  which he proposed a theory called Natural
  Selection
• Definitions
• Variation differences between individual
  members of a population (ex. Color of fur, shape
  of teeth)
• Adaptation an inherited characteristic that
  increases an organisms chance of survival

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Darwins Theory of Natural Selection

• 1. There is a variation within a population
• 2.  Some variations are favorable
• 3.  Not all young produced in each generation
  can survive (struggle for existence)
• 4.  Individuals that survive and reproduce are
  those with favorable variations (survival of the
  fittest)

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EVIDENCE OF EVOLUTION

• According to evolutionary theory, all life
  originated from a common ancestor.
• Common descent the theory that all species were
  derived from common ancestors

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WAYS TO DETERMINE HOW RELATED ORGANISMS ARE
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1. Fossils

• The fossil record reveals changes in populations
  over time and supports the theory of evolution.
• Scientists can calculate a fossils age by using
  radioactive dating or relative dating (we will
  discuss this later)
• The fossil record is incomplete, but it still
  shows us relationships between species and how
  their structures have changed over time.
• Fossils are mostly found in sedimentary rock.

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2. Homologous Structures

• Homologous structures structures that have
  different mature forms, but develop from the same
  tissues
• Ex. Arms, wings, and flippers are all
  constructed from the same basic bones
• Analogous structures structures that share
  common function but NOT common structure
• Ex. Wing of bee bird
• Vestigial structures structures reduced in size
  and often unused
• Ex. Leg/hip bones in pythons or appendix in
  humans

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Homologous Structures
Analogous Structures
Vestigial Structures
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 3. Embryology Biochemistry

• Embryology compare how embryos of different
  species look during certain stages of development
• Biochemistry compare the chemicals that make up
  our body (amino acid)

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GENETICS EVOLUTION

• Gene pool consists of all the genes that are
  present in a population
• Relative frequency the number of times that an
  allele occurs in a gene pool
• Ex. In a mouse population, the dominant allele
  for black fur may appear 40 and the recessive
  allele for brown fur may appear 60
• In genetic terms, evolution is any change in the
  relative frequency of alleles in a population

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GENETIC VARIATION

• 2 Main Sources of Genetic Variation
• 1. Mutations change in a sequence of DNA
• 2. Gene shuffling that results from sexual
  reproduction

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DEFINITIONS

• Species interbreeding populations of organisms
  that can produce fertile offspring
• Speciation formation of a new species
• Reproductive Isolation when members of two
  populations cannot interbreed and produce fertile
  offspring

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How do organisms become isolated?

• 1. Behavioral isolation when 2 populations are
  capable of interbreeding but have differences in
  courtship rituals or other reproductive
  strategies that involve behavior
• 2. Geographic isolation when 2 populations are
  separated by geographic barriers such as rivers,
  mountains or bodies of water

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Speciation in Darwins Finches

• Darwin found over a dozen different species of
  finches on the Galapagos Islands that all evolved
  from a common ancestor
• How?
• A few finches (original species) flew or were
  blown to one of the Galapagos Islands
• Then some birds migrated to neighboring islands
  and because the environments were different they
  adapted to their own environments and became
  separate species

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DARWINS FINCHES

• Darwins Finches are an example of adaptive
  radiation
• Adaptive radiation is when a single species has
  evolved into diverse forms that live in different
  ways

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PATTERNS OF EVOLUTION

• Gradualism small genetic changes that occur
  slowly within a population
• Punctuated Equilibrium suggests that
  populations remain genetically stable for long
  periods of time, interrupted by brief periods of
  rapid genetic change (ex. Peppered moth)

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Convergent Evolution

• The process by which unrelated organisms come to
  resemble one another as they adapt to the same
  kind of environment
• Example fishes and dolphins
• Structures such as dolphins fins and a fishs
  tail fin, look and function in the same way, but
  they do NOT share a common evolutionary history.
  These are called analogous structures.

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Divergent Evolution

• The process where organisms within a species
  become very different and will no longer
  interbreed usually because they live in different
  environments
• Example Red fox and kit fox - similarities in
  structure indicate that they had a common
  ancestor, but as they adapted to different
  environments, the appearance of the two species
  diverged.

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CoEvolution

• The process by which two species evolve in
  response to changes in each other over time
  become so dependent on each other that they
  cannot survive or reproduce successfully without
  the other
• Example Flowers and insects

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Convergent, Divergent or CoEvolution?

• Divergent Evolution
• CoEvolution
• Convergent Evolution