Evolution & Natural Selection

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Evolution Natural Selection

• Chapters 15, 16, 17

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Important people associated with Evolution

• James Hutton (1785)- proposed that earth was
  shaped by geological forces that took place over
  extremely long periods of time. He estimates the
  Earth to be millions of years old.
• Lyell agreed with him and stated that volcanoes
  and earthquakes have and continue to change the
  earth.
• Thomas Malthus (1798) predicted the human
  population would grow faster than the space and
  food supplies needed to sustain them.
• Example War, famine, disease

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Important people associated with Evolution

• Jean-Baptiste Lamark (1809) proposed that
  organisms changed over time due to use and disuse
  of certain organs/parts. The traits that were
  used in an organisms lifetime could be passed
  on to their offspring. His theory was flawed!
• Tendency towards perfection- continually changing
  to be successful.
• Ex birds acquired urge to fly
• Use and Disuse- by using organ eventually change
• Ex birds in order to fly develop wings
• Inheritance of Acquired Traits
• Ex Lift weights build muscles and offspring will
  inherit big muscles

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Important people associated with Evolution

• All of the previous peoples ideas influenced
  Darwins thinking
• Charles Darwin (1831) Set sail on the H.M.S.
  Beagle. This voyage provided him with much of the
  data and evidence that lead to his theory of
  evolution
• Darwins Theory of Evolution would turn the
  scientific world upside down!!!

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Important people in pictures
James Hutton
Charles Darwin
Jean-Baptiste Lamark
Thomas Malthus
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Lamarck vs. Darwin

• http//www.angelfire.com/bug/darwinvslamarck/

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What did Darwin observe???

• Extreme diversity existed among plant and animal
  species around the world.
• The organisms found within a certain area were
  well suited to survive in that environment.
• Living organisms he observed greatly resembled
  fossils that he found on his voyage.

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What did Darwin observe???

• The Galapagos Islands ? This tiny group of
  islands influenced Darwin the most!
• Although the islands were close together, the
  climates and environments differed greatly.
• Similar organism found on different islands had
  varying characteristics, like appearance and
  behavior, this is variation.
• Examples
• Giant Galapagos Tortoises with varying shell
  shape.
• Darwins Finches beak shape differed among the
  birds.

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What did Darwin observe???
10
What did Darwin observe???
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Apaptations

• A trait/characteristic that an organism is born
  with
• All organisms have adaptations that help them
  survive and thrive
• Structural adaptations are physical features of
  an organism like the bill on a bird or the fur on
  a bear.
• Behavioral adaptations are the things organisms
  do to survive. For example, bird calls and
  migration are behavioral adaptations.
• Physiological adaptations are chemical responses
  to stimuli to maintain homeostasis

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adaptations
13
Natural Variation

• Occurs in all populations
• Sexual reproduction increases the chance of
  natural variation because of the gene shuffling
  of meiosis
• Occurs far less frequently in asexual reproduction

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Darwin presents his theory of Evolution

• 1859 Darwin published his work On the Origin
  of Species
• Two main points
• 1. Species were not created in their present
  form, but evolved from ancestral species.
• 2. Proposed a mechanism for evolution
  NATURAL SELECTION
• Humans had been employing artificial selection
  for many years!

15
Artificial Selection

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

16
Evolution by natural selection

• Struggle for Existence
• Survival of the Fittest Fitness results from
  adaptations that give an organism advantages for
  survival. The most fit organisms will survive
  and reproduce passing along the advantageous
  characteristics to their offspring. These
  changes can only be seen after many generations!
• Examples of adaptations that make organisms
  fit
• Descent with Modification As organisms change
  over time they become different, resulting in
  many varied species. This illustrates common
  descent. All living things have a common
  ancestor.

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Evidence that supports Evolution

• Fossil Record
• Older fossils are in lower rock layers
• Geographic Distribution of Living Species
• Species evolve differently based on where they
  live.
• Due to different climate changes adaptations
  resulted in differences.
• Similar areas tended to have similar adaptations

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Evidence that supports Evolution

• Anatomy-body parts
• Homologous Structures
• Wing bat resembles forelimb of mammal, not bird
• Bird wing resembles reptile forelimb
• Analogous Structures
• similar looking but evolutionary
• unrelatred
• Vestigial organs-
• no function now but did have a function
• in ancestors. Ex appendix, tailbone

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Evidence that supports Evolution

• Similarities in Early Development
• Embryos of related ancestors
• are similar in early stages
•  
• Biochemical Evidence
• Common DNA and RNA
• sequences genes

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Speciation

• Definition forming a new species
• What is a species?
• Group of similar organisms that can breed and
  produce fertile offspring.
• Isolating Mechanism
• features of behavior , morphology, or genetics
  which serve to prevent breeding between species.
• Reproductive Isolation
• mechanisms that prevent two or more populations
  from exchanging genes
• Isolating Mechanism Reproductive Isolation
  Formation of a new species

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Major Types of Isolation

• Behavioral Isolation Two separate species are
  capable of interbreeding, but they do not because
  of behavioral differences.
• Example ? Meadowlarks, different songs to
  attract mates courtship
• Geographic Isolation When one species becomes
  separated by some barrier (river, mountain, etc.)
  they may develop into two distinct species over
  time.
• Example ? Squirrel population split by Colorado
  River 10,000 years ago

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Major Types of Isolation

• Temporal Isolation This mechanism occurs when
  species reproduce at different times (different
  mating times).
• Example ?Orchids in the rainforest, only release
  pollen 1 day!
• Reproductive Isolation- Cant interbreed and have
  separate gene pools
• Example ? Lion and a Tiger make a Liger which is
  sterile.

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Evolution Genetics How are they linked???

• Darwin had a disadvantage when he developed his
  theory of evolutionhe did not understand the
  mechanisms of heredity.
•  
• Today, we understand how genes, heredity, and
  evolution all tie together.

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Evolution Genetics How are they linked???

• Gene Pool the combined genetic info of all the
  members of a specific population.
•  
• Genetic Variation is Critical to Evolution
• Mutations
• Gene shuffling as a result of sexual reproduction

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Evolution Genetics How are they linked???

• Single-Gene Traits vs. Polygenic Traits
• Both lead to evolution, but polygenic traits
  (wide variety of phenotypes possible) lead to a
  more complex process of natural selection.
• Genetic Equilibrium when allele frequency
  remains constant in a population.

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Evolution Genetics How are they linked???

• Hardy-Weinberg Principle allele frequency
  remains constant in a population (no evolution)of
  these factors are present in the population.
• Random mating
• Population size very large
• No movement in or out
• No mutation
• No natural selection

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Evolution Genetics How are they linked???

• Three Major Types of Natural Selection
• Directional Selection
• Stabilizing Selection
•  
• Disruptive Selection

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Directional selection

• Form of natural selection by which the entire
  curve moves.
• Occurs when individuals at one end of the
  distribution curve have higher fitness than
  individuals in the middle or at the other end of
  the curve.

Key
Low mortality, high fitness
Directional Selection
High mortality, low fitness
Food becomes scarce.
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Stabilizing Selection

• Form of natural selection by which the center of
  the curve remains in its current position.
• Occurs when individuals near the center of
  distribution curve have higher fitness than
  individuals at either end.

Stabilizing Selection
Key
Low mortality, high fitness
Selection against both extremes keep curve narrow
and in same place.
High mortality, low fitness
Percentage of Population
Birth Weight
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Disruptive Selection

• Form of natural selection in which a single curve
  splits into two.
• Occurs when individuals at the upper and lower
  ends of a distribution curve have higher fitness
  than individuals near the middle.

Disruptive Selection
Largest and smallest seeds become more common.
Key
Population splits into two subgroups specializing
in different seeds.
Low mortality, high fitness
Number of Birdsin Population
Number of Birdsin Population
High mortality, low fitness
Beak Size
Beak Size
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What is Genetic Drift??

• Random change in allele frequency, based on the
  laws of probability. Example ? Founder Effect
• Founder Effect change in allele frequencies as a
  result of the migration of a small subgroup of
  population.

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History of Life

• Fossil Evidence
• Fossils provide proof of changes to life on earth
• Relative dating estimate fossils age compared
  to other fossils
• Radioactive dating age of fossil based on
  amount of remaining radioactive isotopes it
  contains
• Geological Time

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History of Life

• Early History
• Early atmosphere contained carbon dioxide, carbon
  monoxide, nitrogen, water vapor
• Miller and Ureys experiment show how a mixture
  of early atmospheric compounds could produce
  simple organic compounds found in living things
• Rise of oxygen drove some life forms to
  extinction but many evolved and used oxygen for
  respiration and prospered
• Endosymbiotic theory eukaryotic cells arose
  from prokaryotic cells

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History of Life

• Geological Time Table
• Paleozoic Marine life
• Devonian animals invade land
• Mesozoic Dinosaurs and flowering plants
• Cenozoic - Mammals

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History of Life

• Patterns of Evolution
• Mass extinction
•  Adaptive Radiation Single species evolves into
  many species quickly
• Ex. Dinosaurs and mammals
• Convergent evolution unrelated organisms
  resemble each other
• Ex dolphin and shark
• Coevolution 2 species evolve in response to
  changes in each other
• Ex flowers and insects
• Punctuated Equilibrium long stable periods
  interrupted by brief periods of rapid change
• Changes in developmental genes- new research
  shows hox genes are master control genes and
  can control how evolution occurred.

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The Miller-Urey Experiment

• Miller and Urey created a simulation of the
  predicted early atmosphere of the Earth.
• When they combined the atmospheric components
  with electricity, they produced organic compounds
  including amino acids.

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The Evolution of Life

• Some scientists believe that RNA was the first
  genetic information
• The first life forms are thought to be
  single-celled prokaryotes (found from
  microfossils in rock) similar to bacteria.
• Later, photosynthetic bacteria produced oxygen.
• This oxygen combined with iron in the water,
  forming rust, which dropped to the ocean floor
  and left the ocean blue-green
• Most organisms evolved new metabolic pathways
  that would allow them to live in the new
  oxygen-rich environment.

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The Evolution of Life

• Eukaryotic Cells evolved from prokaryotes that
  began evolving internal cell membranes.
• Some small prokaryote then entered a larger
  prokaryote to form a mutualistic relationship.
• These smaller prokaryotes were able to use oxygen
  (aerobic respiration) and evolved into what is
  now our mitochondriarecall that mitochondria
  have different DNA than the rest of the cell.
• This is called the Endosymbiotic Theory.
• The evolution of Sexual Reproduction allowed much
  more genetic variation among eukaryotes.

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The Endosymbiotic Theory

• A descriptive Diagram