Evolution

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Evolution

• Change Over Time
• Chapter 15

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Charles Darwin

• 1809-1882
• Began work in 1831 as a naturalist on the English
  ship HMS Beagle
• South Pacific South America
• 5 year journey
• Studied and collected biological specimen
• Curious about relationships among species

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Galapagos Islands

• Group of small islands
• Near equator
• West coast of South America
• Found animals and plants similar to other species
  but unique to the islands

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Darwins Studies

• 22 years
• Human population grows faster than Earths food
  supply.
• Many species have large numbers of offspring.
• Individuals struggle to survive

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Struggle to Survive

• Compete for space
• Food
• Escaping from predators
• Finding mates
• Locating shelter
• Only some individuals survive the struggle and
  produce offspring.

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Natural Selection

• Artificial Selection Breeding organisms w/
  specific traits to produce offspring w/ identical
  traits.
• Natural Selection Organisms w/ certain
  variations survive, reproduce, and pass their
  variations to the next generation.

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Artificial Selection in My Backyard!
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On the Origin of Species by Natural Selection

• Evolution Any change in the gene pool of a
  population.
• Evidence is overwhelming.

• Darwin published the first book about evolution
  in 1859.
• Alfred Russell Wallace reached a similar
  conclusion from his studies

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Darwins Theory

• Variations exist within populations.
• Some variations are more advantageous for
  survival and reproduction than others.

• Organisms produce more offspring than can
  survive.
• Over time, offspring of survivors will make up a
  larger proportion of the population.

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Direct Evidence

• Adaptation any variation that aids an organisms
  chances of survival in its environment.
• Adaptations develop over many generations.
• Structural Adaptations (ex. Teeth, claws, quills)

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Variety, the spice of life!

• Some organisms within a species exhibit traits
  that differ from others of the same species.
  These differences among individuals in a
  population are called variations. Variations
  occur as a result of sexual reproduction or
  genetic mutations. Variations can be differences
  in appearance (fur color) or function (behavior
  or physiology).

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Mutations

• Mutations are changes in an organisms genetic
  material.
• Adaptive mutations are mutations that make an
  organism better suited to its environment.

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Direct Evidence

• Mimicry structural adaptation that enables one
  species to resemble another species
• Ex. Viceroy Butterfly and Monarch Butterfly

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Direct Evidence

• Camouflage adaptation that enables species to
  blend with their surroundings.

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Direct Evidence

• Evolve more rapidly than structural.
• Physiological adaptations changes in an
  organisms metabolic processes.
• Ex. Penicillin/bacteria
• Ex. Insects Weeds/pesticides

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Indirect Evidence

• Fossils
• Trace the evolution of organisms. Ex. horse
• Embryology
• Embryo earliest stage of growth and development
  of plants and animals
• Ex. Gill slits and tails- fish, reptiles, birds
  and mammals
• Biochemistry
• RNA DNA

• Anatomy
• Homologous Structures structures similar in
  arrangement and/or function-whales, birds,
  crocodiles forelimbs
• Analogous Structures do not have common
  evolutionary origin but are similar in function-
  wings
• Vestigial Structures body structure that has no
  function in present day - appendix

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The Fossil Record

• Fossils are the remains of organisms that lived
  in the past. Where fossils are located in rock
  layers provide clues to how long ago an organism
  lived. The oldest fossils discovered are of
  cyanobacteria found in rocks that are 3.5 billion
  years old.

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Embryology

• Embryology is the study of embryos.
• The embryos of related organisms develop in
  similar ways. In many cases, embryos have
  structures that are not present in the adult
  form. For example, the embryos of fish, chickens
  and humans look very similar and all have gill
  pouches in the neck region.

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• Embryology
• http//www.pbs.org/wgbh/evolution/library/04/2/l_0
  42_02.html

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Mechanisms of Evolution

• Populations evolve not individuals
• Gene Pool all the alleles of a populations
  genes
• Allelic Frequency Percentage of a specific
  allele in the gene pool-same no evolution

• Genetic Equilibrium frequency of alleles
  remains the same over generations.
• Evolution does not occur
• Changes in equilibrium results in evolution

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Mechanisms of Evolution

• Mutations can occur from environmental
  conditions such as radiation chemicals or by
  chance
• Genetic Drift the alteration of allelic
  frequencies by chance small populations

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Natural Selection acts on variations

• Stabilizing
• Favors average individuals
• Reduces variation in population
• Directional
• Favors extreme variations of a trait
• Rapid evolution

• Disruptive
• Favors both extreme variations of a trait
• No intermediate forms of trait.
• May result in 2 new species

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Evolution of Species

• Geographic Isolation
• Physical barrier divides a population
• Reproductive Isolation
• Formerly interbreeding organisms can no longer
  mate produce fertile offspring
• Change in chromosome numbers
• Ex Polyploidy- multiple of the normal set of
  chromosomes
• Polyploids interbreed and form a separate species

• Speciation the evolution of new species.
• Occurs when members of similar populations no
  longer interbreed to produce fertile offspring.

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Rate of Speciation

• Punctuated Equilibrium occurs relatively
  quickly, in rapid bursts with long periods of
  genetic equilibrium in between.
• Environmental changes lead to rapid changes in a
  populations gene pool
• 10,000 yrs or less

• Polyploidy occurs quickly w/in 1 generation
• Gradualism species originate through a gradual
  change of adaptations

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Patterns of Evolution

• Diversity in New Environments
• Divergent Evolution species that once were
  similar to an ancestral species become
  increasingly distinct
• Adaptive Radiation when an ancestral species
  evolves into an array of species to fit a number
  of diverse habitats.

• Different Species can look alike
• Convergent Evolution distantly related
  organisms evolve similar traits

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