Diversity of Life

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Diversity of Life

• Biology 103
• Instructor Jim Driver

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Class Information CardPlease take a few minutes
to fill out a 3x5 card with the following
information

• Name
• Major
• Class (Soph., Jr., etc)
• Related courses taken
• Career goals?
• Expectations of this course
• E-Mail address (optional)

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Course Business

• Instructor Jim Driver (jim.driver_at_mso.umt.edu)
• Required text Biology, Campbell and Reese, 7th
  edition
• Diversity of Life is a continuation of Principles
  of Biology
• A comprehensive syllabus and lecture schedule
  will be provided
• This course will have four exams, one will be a
  take-home

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Course Business

• Classroom attendance is STRONGLY recommended
• Taking clear, concise lectures notes will help in
  this and future university classes
• Exam questions will come from the lecture notes.
  Use the textbook to better understand the
  materials covered in lecture, BUTa thorough
  reading of the text will help in the future and
  may be enjoyable!

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How to study for my exams

• Come to class
• Take notes, pay attention to emphasis on topics
  or concepts
• Use textbook to better understand notes
• Know all terms in notes
• If you have questions - ask during class or come
  see me during office hours

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Yes, life sure is diverse!
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Diversity of Life Course Preview

• Biology of Life covered molecular biology, cell
  biology, and genetics. This course covers the
  rest!
• But seriously, topics we will cover include
• How did life develop such diversity from its
  initial beginnings?
• How is life categorized?
• What are the hallmarks of the major life
  groupings?
• How does life interact on a local, regional, and
  planetary level?

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The molecular structure of DNA

• Holds all the information to make a complex
  organism in 4 bases!

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Diversity and Relationships

• Carolus Linnaeus taxonomy
• How can we put all the organisms in the right
  boxes?
• Developed binomial nomenclature (Genus species)
• He classified similar species (by morphology)
  into increasingly general categories

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What is common thread in each grouping?
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Evolution and Diversity

• Evolution accounts for lifes unity and diversity

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Darwin and descent with modification

• Lamarks theory of evolution
• Use and disuse
• Inheritance of acquired characteristics
• Based on improvement of the individual during its
  life and transmission of the improvements to
  offspring

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What Lamarck thought
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Darwinian Evolution

• 1859 On The Origin of Species By Means of
  Natural Selection (Alfred Russel Wallace also had
  same idea)
• 2 main ideas
• Evolution explains lifes unity and diversity
• Natural selection is a cause of adaptive
  evolution
• Remember
• Individuals survive and reproduce
• Populations evolve and adapt

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Variation - driven by random mutation and
sexual recombination
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Overproduction
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Reproductive success
Imagine an alternative scenario
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How did Darwin get to natural selection?Observati
ons and inferences.

• Obs. 1 all species have great potential
  fertility
• 2 populations tend to remain stable
• 3 resources are limited
• Inference 1 overproduction leads to struggle
  for existence
• Obs. 4 in a population, no two individuals are
  alike
• 5 variation is heritable
• Inf. 2 individuals with inherited traits that
  best fit the environment will likely leave more
  offspring
• Inf. 3 unequal survival and reproduction will
  lead to gradual change in a population, with
  favorable characteristics accumulating over the
  generations

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In other words.

• Natural selection is
• differential success in reproduction
• an interaction between the environment and the
  variability in individuals making up the
  population
• Natural selection leads to the adaptation of a
  population of organisms to their environment

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Evidence for natural selection

• Antibiotic resistance in bacteria
• Bacterial populations are not always clonal
• Mutations in DNA during replication can lead to
  protein structure changes
• Moth coloration in England
• Pollution caused change in tree bark color
• Some moths stood out leading to differential
  predation, changing population
• Pesticide resistance in insect populations
• Toxins in Newts

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Figure 22.12
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The fittest survive and reproduce
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Understand

• Fitness any heritable trait that increases
  relative reproductive success
• Strictly dependent on the specific environment
• Adaptation refers to populations adapting to
  the environment, not the individual
• Scientific Theory useful, comprehensive, and
  well-supported explanation for a wide range of
  observations

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Understand

• Fitness any heritable trait that increases
  relative reproductive success
• Strictly dependent on the specific environment
• Adaptation refers to populations adapting to
  the environment, not the individual
• Scientific Theory useful, comprehensive, and
  well-supported explanation for a wide range of
  observations
• Evolution in its strict meaning is a change in
  allele frequencies in a population over
  time.But

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Evolution change through time
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Definitions

• Microevolution change in allele frequencies in
  population over time
• Alleles - alternative versions of a gene that
  produce distinguishable phenotypic effects
• Speciation a populations genetic divergence
  leads to reproductive isolation
• Macroevolution the level of change of life on
  the planet observed over geological time

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Understanding Evolution

• Evidence indicates that all life on this planet
  is related. Eg. DNA-based
• Later forms show a relationship to earlier forms
  based on common characteristics
• Natural selection provides a mechanism to explain
  how these changes came about
• Natural selection requires heritable variation in
  populations and conditions that favor one variant
  over another

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Evidence for evolution

• Descent with modification can explain
  similarities in structures with different
  functions (homology)
• Anatomical homologies

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Evidence of evolution

• Descent with modification can explain
  similarities in structures with different
  functions (homology)
• Anatomical homologies
• Molecular homologies

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Biogeography

• The geographic distribution of species
• Closely related species inhabit same geographic
  region (common evolution)
• But
• Same ecological niches in distant regions can be
  occupied by evolutionarily different species

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Biogeography

• The geographic distribution of species
• Closely related species inhabit the same
  geographic region
• But these ecological niches in distant regions
  can be occupied by evolutionarily different
  species
• Darwin observed that many species are endemic

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Evolution of Populations

• Chapter 23

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Population genetics

• How do populations change (genetically) over
  time?
• Gene pool total of all genes in a population
• Alleles alternative forms of a gene
• Remember in sexual spp. One gene from mom, one
  from dad

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Mendelian Genetics Review
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Mechanisms of Variation

• Mutations changes in nucleotide sequence of DNA
• Only mutations gametes passed to offspring
• Point mutations - single base change
• Chromosomal mutations - large scale deletions,
  disruptions or rearrangements
• Also gene duplication (eg detecting odors)
• Mutation rates usually low in animals but much
  higher in prokaryotes (eg. HIV)

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Mechanisms of Variation

• Sexual recombination
• Rearranges alleles into new combinations each
  generation (review Chap. 13)
• Remember, one chromosome of each pair from each
  parent
• Do bacteria have sex? YES!
• What does THAT look like?

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Sexual reproduction

• Two parents give rise to offspring that have
  unique combinations of genes inherited from the
  two parents

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Crossing Over (Not on Exam)

• Produces recombinant chromosomes with genes
  derived from two different parents

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Also Independent Assortment (not on exam)

• Each pair of chromosomes sorts maternal and
  paternal homologues into daughter cells
  independently of the other pairs

Figure 13.10
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How populations change

• Natural selection
• Variants better suited to the environment tend to
  produce more offspring
• Or ? Genetic drift population changes
  unexpectedly

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Genetic drift unpredictable changes
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How populations change

• Genetic drift can come about through
• Bottleneck effect a few survivors
• Founder Effect
• A few individuals form an isolated population

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How populations change

• Gene Flow
• Movement of fertile individuals or gametes (eg.
  Pollen) into or out of a population
• Egs, pollen, storms or tsunamis etc.
• Think humans and travel

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Adaptive Evolution and Variation

• Genetic Variation can be
• Discrete characters (either/or)
• Quantitative characters (vary along continuum)
• Measuring variation
• Average heterozygosity (eg. Fruit flies 1800 out
  of 13,000 gene loci,)
• Nucleotide variability, in humans 0.1 of DNA
  bases

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Variation between populations - Geographic
variation in a species can follow a cline
(variation in trait that parallels environmental
gradient)
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Fitness

• contribution individual makes to gene pool of
  next generation
• Relative fitness contribution of one genotype
  compared to alternative at same locus
• based on reproductive success ONLY

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How does natural selection work?

• Directional selection
• Favors extremes at one end of distribution

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Modes of selection
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Natural Selection, again

• Disruptive selection
• Favors extremes at both ends of distribution

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Modes of selection
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Natural Selection, again

• Stabilizing selection
• Removes extremes and favors intermediates (most
  common type)

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Modes of selection
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Preserving variation

• Most eukaryotes are diploid (2 copies of each
  chromosome/gene)
• Homozygous identical genes at a location
• Heterozygous different genes
• Heterozygote advantage sickle cell anemia

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How is it preserved?

• Wouldnt natural selection remove all unfavorable
  genotypes?
• No, due to
• Recessive alleles
• Heterozygote advantage (eg sickle cell)
• Neutral variation (really neutral?)

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Hardy-Weinberg Theorem

• Used to model non-evolving gene pools
• Can be used to determine allele frequencies
  within a population
• Or, what is happening to variation in a
  population
• What is H-W good for?

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H-W Theorem

• - frequencies of alleles and genotypes in gene
  pool remains constant from generation to
  generation if only Mendelian segregation and
  recombination of alleles happens
• Requires
• Extremely large population size
• No gene flow
• No mutations
• Random mating
• No natural selection

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H-W and Sickle cell anemia(no math on exam)

• Eg. In some populations the sickle cell allele is
  20 of all hemoglobin alleles
• H-W p2 2pq q2 1
• p normal hemoglobin (0.8 of population)
• q mutant hemoglobin (0.2 of population)
• p2 (0.8)(0.8) 0.64 or 64 of population
• q2 (0.2)(0.2) 0.04 or 4 population
• 2pq 2(0.8)(0.2) 0.32 or 32 of population

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What if?

• Malaria eradicated
• Change in natural selection?
• Loss of heterozygote advantage?
• Increase in gene flow?

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Sexual selection

• Why sex anyway?
• Lower reproduction rate than asexual
• Provides variation for future selection/adaptation
  
• Can provide short-term variation for disease
  resistance

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Sexual selectioncan lead to differences between
sexes
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Sexual Dimorphism

• If sexual characteristics increase mating success
  then benefit outweighs risk
• showy alleles increase
• Egs. Horns, coloration, displays

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The Evolution of Perfect OrganismsWhy doesnt
it happen?

• What is perfect?
• Evolution is limited by historical constraints
• Adaptations are often compromises
• Chance and natural selection interact
• Selection can only edit existing variation