EVOLUTION

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EVOLUTION
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• Jean Baptiste Lamarck
• - One of the first to propose a
  hypothesis for how species can change.
• Theory of Acquired Characteristics
• - If an organism used a part
  of its body more, it grew bigger (or
  changed).
• - Any learned / acquired traits are then
  immediately passed on to their
  offspring.

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• Charles Darwin
• - Developed his ideas based on his 5
  year voyage as a naturalist aboard the HMS
  Beagle.
• - Wrote the book
• On the Origin of Species
• - Discovered more than 1500
  species on the Galapagos
  Islands.
• What is a species?

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• - Darwins Observations
• Noticed only slight differences between
  species on each island.
• - Adaptations
• A trait which allows an
  organism to survive in its
  environment.
• Could be anything!

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What can you say about each tortoises food
supply?
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• - Darwins Theories
• 1. Natural Selection
• - When an individual(s), best suited
  for its environment, survives, mates
  pass on its genes.
• Factors Involved/Needed
• - Overproduction
• - Variation
• - Competition
• - Those who cant
  survive, die.

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• 2. Artificial Selection
• - When a breeder selects which traits
  are desirable, not the environment.

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• 3. Survival of the Fittest
• - Who is the most fit?
• - The ones who survive to produce
  the most fertile offspring.

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• Evidence for Evolution
• A. Fossil Evidence
• - What is a fossil?
• Trace of a long dead organism.
• - How do they form?
• Organism dies and is quickly
  buried by sediment.
• - How old they are?
• 1. Relative Dating
• 2. Absolute Dating (Half-Life)

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• - Types of Fossils
• 1. Petrified
• - Bone that has been changed to rock.
• 2. Molds Casts
• - Molds are hollow spaces in sediment.
• - Casts are molds filled in with sediment.
  

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• 3. Preserved Remains
• - Organisms which have become fully
  preserved in materials such as ice or tree
  sap.

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• B. Homologous Structures
• - Similar anatomical features shared
  between multiple species.

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Humerus
Radius
Ulna
Carpals Metacarpals
Phalanges
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• C. Analagous Structures
• - Different structures, same function.

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• D. Vestigial Structures
• - Features which no longer serve a
  purpose.

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• E. Embryological Structures
• - Similarity seen in early fetal
  development.

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• F. Biochemical Evidence
• - Similarity in genetic material
  between different organisms.
• Examples DNA between Chimps Humans
• Proteins amongst various species

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• G. Transitional Species
• Ex. Archaeopteryx

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H. Bacterial Evolution in Action

• Bacteria evolves at such a fast rate due to its
  short lifespan.
• Many generations can be observed over a short
  period of time.
• Antibiotic resistant bacteria
• MRSA

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• IV. Conditions which affect Gene Frequencies
• A. The sum of all genes in a population
  is referred to as the Gene Pool.
• B. If a population is in equilibrium, it will
  not evolve. Gene frequencies are
  equal.
• C. 5 Factors that Affect Gene Pools
• 1. Mutations
• - Introduces new alleles which can
  spread quickly if advantageous.

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• Genetic Drift
• - Random changes in allele frequencies.
• - Mainly affects small populations.
• (Microevolution)
• - Can result in the founder effect.-migration
  of a small subgroup of a population.

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• 3. Gene Flow / Migration
• - Genes moving in and out of a
  population.
• Immigration- individuals entering a population
• Emigration- ind. leaving a population

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• 4. Non-Random Mating
• - When organisms mate based on specific
  traits.
• Ex Height, Strength, Blue Eyes, Skin Color,
  etc.

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• 5. Natural Selection
• - The environment itself dictates the
  change in a population.
• Three Types
• a. Stabilizing
• - Selects the average traits in a
  population.

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• b. Directional
• - Favors one extreme.
• c. Disruptive
• - Favors both extremes

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Single Gene vs Polygenic Traits

• Single gene trait- controlled by a single gene
  with 2 alleles.
• You either have it or you dont.
• Ex- widows peak, hitch hikers thumb
• Polygenic trait- controlled by 2 or more genes.
• Ex- height, hair color

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• Pattern, Speed and Formation of Species
• A. Patterns
• These mainly occur within large
  populations (macroevolution).
• 1. Coevolution
• - When two or more species evolve
  closely together.

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• 2. Convergent
• - The environment selects which traits are
  beneficial.
• - Dissimilar and/or similar species evolve
  similar traits.

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• 3. Divergent
• - When two or more related species become
  more and more dissimilar.
• Two Types
• a. Adaptive Radiation
• - When many species evolve from the
  same species.
• Ex Galapagos Finches
• b. Artificial selection
• - When an organism is bred for a
  specific trait(s).
• Ex Dogs from grey wolves

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• B. Formation of New Species (Speciation)
• 1. Reproductive Isolation- members of a
  population can no longer interbreed.
• Geographical- When a population evolves into
  separate species due to a physical barrier.

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• b) Behavioral-
• have ability to interbreed but do not due to
  different courtship rituals.
• Ex- Eastern and Western Meadowlark

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Reproductive Isolation Cont.

• c) Temporal-
• When species mate at different times.
• Ex- 3 different orchids produce pollen on 3
  different days.

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• C. Speed of Evolution
• 1. Gradualism
• (Macroevolution Large Populations)
• - Speciation over very long periods of
  time.
• - Usually millions of years.
• 2. Punctuated Evolution
• (Microevolution Small Populations)
• - Speciation occurs quickly
• - Can take only hundreds to thousands of
  years.

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