The Fossil Record, Phylogeny and Systematics

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The Fossil Record, Phylogeny and Systematics
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Phylogeny and Systematics

• Phylogeny - Tribe/Origin
• Study of evolutionary history of species
• Tracing the origin of species
• Systematics Study of biological diversity
• Done in an evolutionary scale and scope
• Focus on Fossil Record, Global Change over time

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The Fossil Records

• Fossils are arranged in the strata of sedimentary
  rock
• Oldest layers on the bottom, newest on top
• Occurs at intervals
• Different periods of sedimentation form strata
• Mark the passing of Geological Time
• Tiny fraction of living organisms become fossils

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Fossil Review
4 Types of Fossils Cast Mold Imprint Actual Body
Parts
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Geological Time

• Fossils in strata are representative orgs from
  that time period
• Index Fossils Fossils in one strata can be
  compared in age (geo time) to fossils in other
  strata
• Geological Time Scale based on strata layering,
  scientists can determine historical periods
• Layers not complete gaps
• Sea level may have effected whether sedimentation
  formed at all, etc

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Geoloigical Time Scale

• Periods of strata are organized into 4 Eras
• Precambrian
• Paleozoic
• Mesozoic
• Cenozoic
• Boundaries of Eras are marked by explosions of
  new fossil species
• Organization done by Relative Dating
• Comparison of index fossils
• Older fossils in deeper strata
• Vary in length based on fossil record
  characteristics
• Eras divided into Epochs

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Table 25.1 The Geologic Time Scale p. 467
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Absolute Dating

• Age of Fossils in years
• Radiometric Dating
• Charts the decay of isotopes present in all forms
  of life
• Half life of years for ½ of amount of element
  originally present in org to decay
• Carbon 14 5600 years
• Uranium 238 4.5 billion years
• Amino Acid Conversion know the rate of
  conversion
• Only certain structure made during life (L-type)
• Measure amount of amino acids converted to dead
  structure (R-type)

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Fossil Record Uses, Problems

• NOT representative of all species ever lived
• Skewed in favor of orgs that lived long, had hard
  parts, abundant and widespread
• DOES document phylogeny over vast time
• Sequences biological change over time
• Can be dated
• Charts environmental changes chronologically

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Phylogeny and Continental Drift

• Biogeography distribution of species with
  adaptation specific to their environments
• Continental Drift movement of earths surface
  by hot mantle currents
• Affected geo distribution of life
• Fossil records on different continents correlate
• Evolutionary Episodes affected as well
• Mass extinction
• Explosive increases

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Figure 25.4 The history of continental drift p.
470
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Pangea

• End of Paleozoic Era (250 MYA)
• Plates brought all earths land together
• Called Pangea means all land
• Supercontinent
• Major Environmental Change
• Ocean Basin Deepened draining shallow waters
• Terrestrial weather draughts, erratic
• Caused extinction
• Selection for orgs that were adapted, survived

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Continental Drift

• Mesozoic Era (180 MYA)
• Pangea breaks up, drifts
• Each continent becomes separate evolutionary area
• Distinct barriers, biogeography
• Divergent evolution based on new environments
• Ex Australian Marsupials
• Evolved and Migrated from N. America during
  Pangea
• During Drift, marsupials separated with Australia
• Unique species formed due to environment

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Mass Extinctions and Adaptive Radiations

• Adaptive Radiations explosion in diversity and
  species number
• Follow Introduction of Evolutionary Novelty
• Follow Environmental Change
• Follow Mass Extinctions reducing of orgs
• Adaptive Zone Habitat or place which opens up to
  orgs
• Changes Predator/Prey Relationship
• Changes biogeography of org
• Ex Wings in insects opened up areas reachable by
  flight
• Cambrian Explosion hard parts develop,
  diversity of sea animals increases
• Pre-cambrian Extinction shown in fossil record
• Explosion of new species, characteristics seen in
  Cambrian Period

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Examples of Mass Extinction

• 1. Permian Extinction (250 MYA)
• Boundary between Paleozoic and Mesozoic Eras
• 90 marine animals extinct, reduction in insects
• Occurred in 5 million years quick!
• Radical Environmental change
• Pangea broken up
• Extreme volcanic activity
• High levels CO2 in atmosphere
• Global warming of climate
• Temp. discrepancies reduced ocean mixing
• Reduced amount of Oxygen in water

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Figure 25.5 Diversity of life and periods of
mass extinction
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Examples of Mass Extinction

• 2. Cretaceous Extinction 65 MYA
• Boundary between Mesozoic and Cenozoic Era
• Marine, terrestrial animals (Dinos), plant life
• Impact Hypothesis Asteroid strike cause dust
  cloud which blocked sun darken for years
• Evidence Clay between Meso/Ceno has Iridium
• Large crater in Chicxulub Mexico
• Actual impact (quick) severe extinction in
  proximity
• Global (slower) Climate cooled, photosynthetic
  orgs died
• Led to differing extinction rates in the same
  period
• Debate still over environmental change theory vs.
  impact

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Figure 25.6 Trauma for planet Earth and its
Cretaceous life
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Figure 25.6x Chicxulub crater
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Phylogeny and Systematics

• Phylogeny - Tribe/Origin
• Study of evolutionary history of species
• Tracing the origin of species
• Systematics Study of biological diversity
• Done in an evolutionary scale and scope
• Focus on Fossil Record, Global Change over time

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Timeline of Classification

• 1. 384 322 B.C. Aristotle
• 2 Kingdom Broad Classification
• 2. 1735 - Carl Linnaeus
• 2 Kingdom Multi-divisional Classification
• Kingdom, Phylum, Class, Order, Family Genus,
  Species
• 3. Evolutionary Classification (After Darwin)
• Group By lines of Evolutionary Descent
• 4. 5 Kingdom System 1950s
• 5. 6 Kingdom System 1990s
• 6. 3 Domain System 1990s

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Modern Taxonomy Carl Linnaeus

• Carl Linnaeus (1735) Swedish Botanist
• Reworked Classification system from Aristotles
  basic Kingdom System
• Called his classification Systema Naturae
• Used Comparative Morphology
• Used a hierarchy of categories to classify
• Binomial Nomenclature Genus species
• Ex Homo Sapien

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Figure 25.7 Hierarchical classification
Overview of Classification Systems Linnaeus
Kingdom Species Modern Classification Added
Domain after rRNA sequences est. and compared
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Example Classification

• Lion DOMAIN EUKARYA
• Kingdom Animalia (all Animals)
• Phylum Chordata (All vertebrate animals)
  Class Mammalia (All Mammals mammary glands)
• Order Carnivora (Meat eaters)
• Family Felidae (includes all Cats)
• Genus Panthera (Includes all roaring Cats)
• Species leo (Lions)

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Taxons

• Within each category, a particular group is
  called a Taxon
• Many Taxons for each category
• Carnivora is the Taxon for the Order category in
  Lions

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Tools Used to Classify Organisms

• 1. Comparative Morphology
• Compares Physical Structures, Traits
• 2. Evolutionary Relationships
• Related Organisms with common ancestors, Derived
  Characters
• 3. DNA/RNA comparison

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Phylogeny

• Goal of systematics Classification reflects
  evolutionary history
• Relation of modern orgs. Shown
• Common Ancestors indicated
• Divergent characteristics ( derived characters
  determined)
• Show this by constructing Phylogenetic Trees

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Phylogenic Trees

• Diagrams that trace evolutionary relationships
  between the Taxons
• Use fossil record and extant (living) orgs
• Comparing Homologous DNA
• Homologous DNA sequences in specific parts the
  same
• Can determine where mutations (new
  characteristics) have occured - of mutations is
  the evolutionary distance
• Few differences close relation
• Ex Mitochondrial DNA
• Compare Protein Amino Acid Sequences
• DNA sequences
• DNA-DNA hybridization
• DNA sequence analysis

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Figure 25.14 Simplified versions of a
four-species problem in phylogenetics
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Figure 25.15b Parsimony and molecular
systematics (Layer 3)
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Molecular Clock can Determine Relationships and
Derived Characters of Species
New mutations (or characteristics) are added over
evolutionary time the more recent the organism,
the more mutations are seen
Like Derived Character -
We Know how newer species are related to ancestor
orgs due to mutation patterns
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Classification Key

• Also Known as
• Dichotomous Key, Biological Key
• Useful in Identifying Organisms in the field
• Based on Comparison of Morphological Traits
• Use physical features to compare, contrast
• Determine if Organism is in group or not, based
  on Key criteria
• At each level you only have a few contrasting
  characteristics to choose from
• Body shape plans, Characteristics such as fur

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What are these organisms and how are they
classified?
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Cladistics

• Part of Systematics
• Clade evolutionary branch
• Organizes Orgs. In order of evolution
• Defined by novel homologies
• Introduced characteristics called derived
  characters
• Shows evolution of orgs as well as the novel
  characters which define their grouping

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Cladogram vs. Comparative (Traditional)
Morphology p.452
Derived Characters
Common Ancestor ?
lt-- Common Ancestor
? ?
Common Ancestor ?
Common Ancestor ?
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Outgroup Comparison

• Outgroup org. related but not closely to orgs
  of interest
• Outgroup org. has basic characteristics of orgs.
  Of interest
• Orgs of interest have derived characters which
  differentiate from Outgroup org.
• Outgroup and interest orgs compared
• Characteristics in common suggest presence in
  common ancestor
• Those characters are shared primitive characters

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6 Kingdom System
Animalia Plantae Fungi Protista Eubacteria Archaea
bacteria
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From 2 Kingdoms to 6p. 458
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Three Domain System

• 1990s
• Domain is larger classification than Kingdom
• Used Technology to compare Ribosomal RNA
  sequences of organisms from bacteria to animals
• Determined how long organisms had been evolving
  independently
• Shows Evolutionary Relationships
• Uses molecular clock to determine how long ago
  orgs were related
• Based on how many sequences are different ( of
  mutations, order of mutations)

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4. Three Domain System

• 1. Domain Bacteria
• Corresponds to Eubacteria Kingdom
• Unicellular Prokaryotic Organisms
• No Nucleus
• Ecologically Diverse live everywhere!
• Metabolically Diverse
• Cell Walls contain substance called Peptidoglycan
  special protein and sugar
• Trait used to distinguish between
• Bacteria and Archaea
• Target of many Antibiotics

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Three Domain System

• 2. Domain Archaea Ancient Bacteria
• Corresponds to Kingdom Archaeabacteria
• Unicellular, Prokaryotes
• Metabolically Diverse
• No nucleus
• Live in Extreme environments like those of early
  Earth
• Cell walls without Peptidoglycan
• A trait used to distinguish between Archaea and
  Bacteria Domains

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Three Domain System

• 3. Eukarya
• Contains Kingdoms
• Protista, Fungi, Plantae, Animalia
• Eukaryotic, single or multi-cellular Organisms
• Nucleus
• Most visible life
• Humans are in Domain Eukarya

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Three Domains of LifeP. 460-461