AP Biology Exam Review

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AP Biology Exam Review

• Heredity and Evolution 25

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Evolutionary biology 8

• Early evolution of life
• Evidence of evolution
• Mechanisms of evolution

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Related fields of study

• Paleontology study of fossils
• Comparative anatomy study of structural
  similarities among organisms
• Comparative embryology study of embryological
  similarities among organisms
• Taxonomy study of organism groupings with
  similar homologous structures (including
  vestigial organs)
• Biochemistry chemical reactions in living things

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Terminology

• Population localized group of individuals of the
  same species
• Species group of population whose individuals
  have the potential to interbreed and produce
  fertile offspring
• Gene pool total aggregate of all genes in a
  population at any given time

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Tenets of evolution

• Natural selection edits the available gene pool
  for a species.
• Natural selection is contingent upon time and
  place. Certain variations in a population (group
  of species residing in one area) are more favored
  for survival than others.
• Mutations are a sources of variation in a
  population.
• Descent with modification

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DDT Insects

• Insects with DDT resistance also have reduced
  metabolism.
• Without DDT present, these insects are not
  adapted for the environment.

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Homology vs. Analogy
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Three kinds of homologies having common origin

• 1. Anatomical homology example, forelimbs
• 2. Embryological homology example, Eustachian
  tube in humans and all mammals
• 3. Molecular homology DNA, RNA as genetic code
  (shown through RFLP analysis)

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Molecular homology

• Human hemoglobin has 146 amino acids total.

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Sugar glider vs. Flying squirrel
Convergent evolution
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Genetic drift
Changes to allele frequencies in population due
to random chance
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Bottleneck effect

• Genetic drift due to drastic reduction in allele
  frequencies

What factors can cause bottleneck effect?
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The founder effect

• Members from a larger population colonize an
  isolated region. (Ex primary, secondary
  succession)
• Ex 15 people founded a British colony in 1814,
  midway in the Atlantic Ocean. One colonist had
  retinitis pigmentosa, a recessive degenerative
  blindness. Today, there is a higher frequency of
  this disorder than most places on Earth.

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Gene flow

• Genetic exchange due to migration of fertile
  individuals or gametes between populations
• Ex wind carrying pollen grains with sperm from
  plant to far off locations

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Mutations

• Changes to an organisms DNA
• Changes in the DNA, if occurring in gametes, can
  be passed down to the next generation.
• Quantitative changes to the population can only
  result if organisms with the mutation produce a
  disproportionate number of offspring.

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Variations in the population

• Polymorphism For any characteristic, there are
  more than two morphs (forms).
• A variation of the characteristic can only be
  considered one of the morphs if there is a high
  enough frequency in the population.

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Measuring diversity

• Gene diversity measuring whole gene differences
• Nucleotide diversity measuring differences at
  the molecular level (using RFLP analysis or
  genomic comparisons)

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Geographic diversity

• Differences in gene pools between populations or
  within subgroups of populations
• Cline graded change in some trait along a
  geographic axis

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Cline
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What preserves variation

• Mutation
• Sexual recombination (meiosis)
• Diploidy
• Balanced polymorphism ability to maintain stable
  allele frequency (established through
  heterozygote advantage and frequency-dependent
  selection)
• Neutral variation

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Directional selection
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Limitations of natural selection

• 1. Limited to historical constraints
• 2. Adaptations are often compromises.
• 3. Not all evolution is adaptive.
• 4. Selection can only edit existing variations.

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Hardy-Weinberg equation of non-evolution

• No natural selection
• No mutation
• No migration
• Large population
• Random mating
• p2 2pq q2 1
• p q 1

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Hardy-Weinberg equation

• p frequency of dominant allele in the
  population (A)
• q frequency of recessive allele in the
  population
• p2 AA (homozygous dominant genotype)
• 2pq Aa (heterozygous genotype)
• q2 aa (homozygous recessive genotype)
• p2 2pq dominant phenotype
• q2 recessive phenotype

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Sample H-W problem

• Hint to solving these equations LOOK FOR THE
  PERFECT SQUARE!! SOLVE FOR Q!
• In a population of 100 individuals, 91 in the
  population show the dominant phenotype. What is
  the frequency of the dominant allele in this
  population?
• (100 91)/100 recessive phenotype q2
• .09 q2 q .3 pq 1 p .7

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The Origin of Species

• In what circumstances would new species evolve
  from preexisting species?

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Reproductive barriers helps to preserve species.

• Any factors that impedes the reproduction of
  members within a species
• Without the ability to breed together, the gene
  pool is isolated. (no migration)

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Two types of barriers

• Prezygotic barriers prevents fertilization of
  ova (egg)
• Postzygotic barriers following fertilization,
  hybrid zygote unable to develop into viable
  offspring

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Prezygotic barriers

• Habitat isolation
• Behavioral isolation
• Temporal isolation
• Mechanical isolation
• Gametic isolation

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Postzygotic barriers

• Reduced hybrid viability
• Reduced hybrid fertility
• Hybrid breakdown

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Other definition of species

• Ecological niche (set of environmental resources
  an organism uses)
• Pluralistic more than one way to define species
• Morphological organisms with unique set of
  structural features
• Geneological organisms with unique genetic
  history

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Interrupting gene flow

• Changes to the gene pool can ultimately lead to
  evolution of new species.
• This is called speciation.

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Patterns of speciation

• Anagenesis phyletic evolution, accumulation of
  heritable change in a population
• Cladogenesis branching evolution, (basis for
  biological diversity)

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Three modes of speciation

• Allopatric speciation geographic separation
  leads to new species if organisms evolve
  reproductive barriers
• Sympatric speciation small population within
  parent population becomes new species
• Adaptive radiation ancestral species colonize an
  area where diverse geographic or ecological
  conditions are available, rapid evolution

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Allopatric vs. Sympatric

• What factors can lead to each type of speciation?

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Allopatric speciation

• Geographic barriers (mountains, valleys, etc) can
  separate the ability for breeding between members
  of the same species.
• Ring species species that seemingly are in the
  gradual process of divergence from a common
  ancestor

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Adaptive radiation

• Much like allopatric speciation
• Island chains have geographic isolation but are
  close enough for occasional have hybrids between
  populations.

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How reproductive barriers evolve

• Diane Dodds experiment showing allopatric
  speciation leading to reproductive barrier
  (therefore new species)

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Allopatric speciation
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Sympatric speciation in plants

• Autopolyploid organism with more than normal
  chromosome due to meiotic failures.
• 4N can breed with 4N ? 8N offspring (polyploid)
• In one generation, postzygotic barriers form,
  causing reproductive isolation.

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Allopolyploid

• Members of two different species create a hybrid
  that cannot back breed with parents. The hybrid
  is more vigorous (hybrid vigor) enables hybrid
  to reproduce asexually ? may eventually evolve
  sexual reproduction.

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Sympatric speciation

• Fishes in Lake Victoria (East Africa) demonstrate
  that females may select mates based on
  coloration.
• Overtime, the nonrandom mating leads to
  behavioral isolation, and a new species of fish
  arise within the parental population.

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Punctuated equilibrium

• Sudden appearance of organisms in the
  phylogenetic tree

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Micro vs. Macroevolution

• Microevolution changes in gene (allelic)
  frequency over generations Hardy Weinberg
• Macroevolution level of change in organisms that
  is evident in the fossil record (requires long
  period of time)
• Speciation bridges microevolution and
  macroevolution.

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Patterns of evolution

• Divergent evolution Two or more species
  originate from the same ancestral species.
• Convergent evolution Two unrelated species share
  many characteristics.
• Parallel evolution Two related species after
  divergence evolve similar characteristics.
• Coevolution symbiotic relationships

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Origin of life

• Oldest fossils 3.5 billion years old,
  indicating maybe oldest life form 1 billion years
  old
• Cyanobacteria earliest fossilized organisms
• Common metabolic pathway in all organisms
  glycolysis
• Primitive atmosphere hydrogen, methane, ammonia,
  water vapor (reducing atmosphere)

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Chemical evolution

• 1. Earth and its atmosphere formed.
• 2. Primordial seas formed.
• 3. Complex molecules synthesized.
• 4. Polymers and self-replicating molecules were
  synthesized. (proteinoids)
• 5. Organic molecules were concentrated and
  isoaltred into protobionts.
• 6. Primitive heterotrophic prokaryotes formed.
• 7. Primitive autotrophic prokaryotes formed.
• 8. Oxygen and ozone layer formed.
• 9. Eukaryotes formed.

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Endosymbiotic theory

• Mitochondria and chloroplast have their own
  circular and naked DNA.
• M C ribosomes similar to bacteria.
• M C divide independently much like binary
  fission.
• Thylakoid membranes of chloroplast resemble
  membranes of cyanobacteria.

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Origin of life experiments

• Oparin and Haldane able to produce coacervates
  that could take in enzymes predicted simple
  molecules form when oxygen absent
• Stanley Miller able to synthesize simple organic
  compounds with flash of electricity
  (lightning) tested Oparin and Haldanes
  hypotheses
• Melvin Calvin complex molecules formed from
  polymerization
• Sidney Fox microspheres (protenoids)

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Chemical selection

• Aggregates with most stable compounds remained.
• Chemical reactions that preserved aggregates
  enabled aggregates to remain.
• Nonliving ? living able to store and use energy
  (metabolism), able to pass on genetic information

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Hydrogen pumps

• Believed to be the first enzymatic proteins
  (light-driven) to provide coacervate energy
• ETC of respiration and photosynthesis formed

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Why RNA before DNA

• RNA has extra OH group on 2 carbon.
• It is able to bind amino acids to allow for
  translation (genetic material ? protein enzymes)

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Earliest organisms

• May have been heterotrophs
• As O2 generated in atmosphere from
  photodissociation (H2O)
• H2O2 may have formed ? killing off heterotrophs
• Cyanobacteria increased in gene pool, forming
  ozone layer.
• Aerobic respiration may have evolved.
• Heterotroph-autotroph hypothesis