Darwin and Evolution

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Darwin and Evolution

• Evidence
• Origin of Life
• Adaptation and Speciation

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Origin of Life

• Formation of organic compounds
• First and Later organisms
• Oxygen revolution

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Formation of organic compounds- Theory

• Earths early atmosphere probably contained
  hydrogen cyanide, carbon dioxide, carbon
  monoxide, nitrogen, hydrogen sulfide, and water.
• Free oxygen was not abundant until about 2
  billion years ago, after the first life forms
  evolved
• UV radiation and lightening bombarded the
  atmosphere causing organic compounds to form.

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Organic Molecule Hypotheses

• Miller-Urey Experiment
• A lab model was used to represent the conditions
  of early Earth. The experiment demonstrated that
  organic molecules can be made from inorganic
  molecules amino acid like.

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An RNA World

• A new hypothesis supports the idea that early
  genetic material was RNA rather than DNA.
• RNA can replicate itself without enzymes.
• Ribozymes are RNA molecules that catalyze
  chemical reactions making organic molecules.

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The first organisms

• Believed to have evolved in the ocean
• Performed anaerobic respiration (no free oxygen
  in the atmosphere)
• Single-celled prokaryotes

Later organisms

• Autotrophs
• Photosynthesis
• Chemosynthesis uses the energy from chemical
  reactions to produce food

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Oxygen revolution

• Photosynthesis produced oxygen
• Aerobic respiration could take place providing
  more energy
• Different types of organisms could then evolve

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Endosymbiotic Theory

• Eukaryotes evolved about 1.5 billion years ago
• What is the difference between a prokaryote and
  eukaryote?
• Endosymbiosis a relationship in which one
  organism lives within the body of another and
  both benefit from the relationship

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Geologic Time
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Darwin and Evolution

• Evidence
• Origin of Life
• Adaptation and Speciation

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What is Evolution?

• change over time
• e.g. humans are taller, resistant bacteria

What is a Theory?

• Well-supported, testable explanation or phenomena
  that have occurred in the natural world

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Historical Context of Evolutionary Theory

• Linnaeus Natural Theology
• -discovery of a Creators plan through the
  classification of species
• - grouped organisms by their similarities

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Historical Context of Evolutionary Theory

• Lamarck Environmental Influence
• Inheritance of Acquired Characteristics
• Early explanation of mechanism of evolution
• Proposed that all organisms evolved toward
  perfection and complexity
• He did not think that species became extinct
• Changes in an environment caused an organisms
  behavior to change

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Historical Context of Evolutionary Theory

• Hutton Gradualism
• profound change is the cumulative product of
  slow but continuous processes (ex. Canyons carved
  by rivers)
• Lyell Uniformitarianism
• geologic processes have constant rates through
  time (ex. Rock strata)
• Malthus Population Trends
• if population continues to grow unchecked,
  eventually we will run out of resources

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Darwins Voyage

• H.M.S. Beagle (1831) as the ships naturalist
• collected plant and animal specimens
• collected fossils
• some resembled organisms still alive
• some were completely unknown

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Darwins Voyage

• Galapagos Islands (west of South America)
• found giant land tortoises, marine iguanas and
  finches with differently shaped beaks

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Darwins Voyage

• Returned to England in 1836
• discovered that the organisms found on the
  Galapagos were found nowhere else
• BUT, each species looked like similar species
  found on the mainland

• 1859 he published On the Origin of Species
• Proposed the idea of natural selection
• struggle for existence
• survival of the fittest live to reproduce

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Main points associated with natural selection

• 1.  Individuals of any population vary from one
  another even siblings differ.2.  These
  variations can be inherited.3.  Populations
  produce more offspring than the environment can
  support.4.  Those individuals with favorable
  variations are likely to leave more
  offspring.5.  The passing on of favorable
  variations leads to the population evolving
  gradually.

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Main Points (continued)

• 6. Individuals dont evolve - populations do.
• 7. Natural selection only amplifies or
  diminishes heritable traits. It edits rather than
  creates.
• 8. Evolution is NOT goal-directed.

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Adaptation

• Structural
• Physiological
• Behavioral

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What is an adaptation?

• Any trait that aids the chances of survival and
  reproduction of organisms
• Variations vs. Adaptations
• Adaptations are products of evolution by natural
  selection (always good)
• Variations are the raw materials upon which
  natural selection acts (can be good or bad)

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Complex adaptations

• e.g. the eye
• Does not arise overnight
• Occurs over many, many generations
• Does not invent, but modifies what already exists

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Speciation

• Formation of a new species

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What is a species?

• A group of organisms that can interbreed and
  produce fertile offspring in nature
• Mules, ligers and tiglons are not considered
  species

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Evolution of a species

• Geographic isolation - geological change (river,
  canyon, or mountain) that isolates segments of a
  population
• Reproductive isolation the inability to
  exchange genes among species

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Evolution of a species

• Divergent evolution when one species evolves
  into two or more species with different
  characteristics
• Convergent evolution species that are not
  closely related evolve similar traits (dolphin
  and fish)
• Coevolution occurs when two species evolve
  together

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Evolution of a species

• Genetic drift rapid changes in the numbers and
  kinds of genes in a small, isolated population
• Adaptive radiation the divergent evolution and
  adaptation of species to different roles in new
  habitats

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What is a population bottleneck?

• event in which a significant percentage of a
  population or species is killed or otherwise
  prevented from reproducing they increase
  genetic drift may increase inbreeding linked
  to speciation

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Tempo of speciation

• Gradualism slow steady change in species
• Punctuated equilibrium slow evolution
  punctuated by short events of rapid evolution

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Biodiversity

• The degree of variation of life

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Evidence for Evolution

• Fossils
• Anatomy
• Embryology, Biochemistry, Genetics

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Fossils

• Evidence of organisms that lived long ago
• Parts or whole organisms are preserved or
  petrified
• Frozen in ice, enclosed in amber, sand or clay
  that turns to rock

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Dating Fossils

• Relative Dating estimates the time during which
  an organism lived based on the placement of other
  fossils.
• Radiometric Dating technique that uses the
  natural decay of unstable isotopes
• Isotope same element/different of neutrons
• Half-Life the amount of time it takes for half
  of the isotope to decay into a different element
  Carbon is often used to date organic substances.

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Fossil record

• Layering in sedimentary rock clues as to when
  organisms lived
• Lower layers are older than upper layers

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Anatomy

• comparative anatomy study of structures of
  different organisms
• vestigial organs structures that have no
  function in the living organism (appendix)
• homologous parts similar in structure but
  appear in different organisms and have different
  functions.

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Anatomy

• Analogous structures structures that perform
  similar functions but are not similar in origin.

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Anatomy vs Physiology

• Anatomy A branch of science concerned with the
  bodily structure of an organism.
• Physiology A branch of science concerned with
  the way an organism or bodily structure functions

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Embryology and Biochemistry

• comparative embryology study of developing
  organisms
• embryos start out very similar, but as they
  develop, they become distinct
• comparative biochemistry studies of organisms
  on a biochemical level (proteins, DNA)

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Genetics

• production of new alleles and genetic
  recombination
• mutations
• selective breeding
• DNA similarities

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• A gene pool is the combined genetic information
  of all the members of a particular population. 
  It contains 2 or more alleles for each
  inheritable trait. 
• The relative frequency of an allele is the number
  of times that allele occurs in a gene pool
  compared with the number of times other alleles
  occur. 

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What is the founder effect?

• When a few individuals with rare alleles produce
  a population with frequencies different from
  those expected for the population.

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What is the Hardy-Weinberg Principle?

• Under certain conditions, the genotype
  frequencies of a trait for a particular
  population stay relatively the same (gene
  frequencies remain constant)

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• The Hardy-Weinberg principle states that allele
  frequencies in a population will remain constant
  unless 1 or more factors cause those frequencies
  to change.  This is called genetic equilibrium. 

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Five conditions are required to maintain this
from generation to generation

• 1. Random mating 2. Large population size3.
  No migrations4. No mutations5. No natural
  selection

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What is artificial selection?

• When humans choose the best organisms to
  reproduce for the next generation (farmers
  choosing a bull to mate with all of the cows).

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What is antibiotic resistance?

• The ability of bacteria or other microbes to
  resist the effects of an antibiotic.

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How does evolution lead to antibiotic resistance?

• Antibiotic resistance occurs when bacteria change
  in some way that reduces or eliminates the
  effectiveness of drugs, chemicals, or other
  agents designed to cure or prevent infections.
  The bacteria survive and continue to multiply
  causing more harm.

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