LIMITATIONS OF SCIENCE

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LIMITATIONS OF SCIENCE

• The external world, not internal conviction, must
  be the testing ground for scientific beliefs
• Cannot provide moral, aesthetic, or philosophical
  standards (Science ? Theology)
• Conflict with supernatural beliefs
• Copernicus (Earth revolves around Sun)
• Darwin (All life has common origin)

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5 steps of the SCIENTIFIC METHOD (1)
Observations (or results of earlier tests) (2)
Question(s) about unclear aspects of the
observations (3) Hypotheses or tentative
explanations of question(s) Must be
falsifiable (4) Predictions developed by the use
of deductive reasoning Specific (if...then)
statement (5) Tests of predictions (experiments
and analysis) SUPPORTED or REJECTED
MORE TESTS
ALTERNATIVE HYPOTHESIS
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Observations
Question
Hypothesis 1 Dead batteries
Hypothesis 2 Burnt-out bulb
Prediction Replacing batteries will fix problem
Prediction Replacing bulb will fix problem
Test prediction
Test prediction
Test falsifies hypothesis
Test does not falsify hypothesis
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Scientific Theory
Can never prove a hypothesis, can only support
it by not disproving it!

• A hypothesis that has been tested for its
  predictive power many times and has not yet been
  disproved (always supported)
• Considered a reproducible scientific fact
• (ex) Theory of Gravity

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Where does life come from?

• Additional Text Material
• Chapter 13 (13.1-13.6, 13.13-13.15)
• Chapter 14 (14.2-14.3)
• Chapter 15 (15.3, 15.14-15.19)

• BIOGENISIS ?
• Living things come from other living things
• SPONTANTEOUS GENERATION ?
• Living things arise from non-living things
• Vital Force

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Francesco Redi (1600s)

• Noticed that maggots usually appear where he saw
  adult flies had landed
• He questioned spontaneous generation (designed
  experiment to disprove)
• Flies only come from eggs laid by other flies
• Disproved spontaneous generation for large
  organisms

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Lazzaro Spallanzani (1700s)

• Microscopes allow for observation of
  microorganisms
• Hypothesized that microorganisms formed from
  other microorganisms
• Disproved spontaneous generation for
  microorganisms
• BUT.some claimed experiment flawed (Vital Force
  destroyed)!

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Louis Pasteur (1800s)

• Some scientists still believed in Spontaneous
  Generation !
• French Academy of Sciences offered prize to any
  scientist who could finally resolve the issue
  through controlled scientific investigation
• Disproved spontaneous generation for
  microorganisms once and for all

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• Cells are the fundamental units of LIFE
• Prokaryotes are smaller and less complex than
  eukaryotes and lack a nucleus and other
  organelles
• Eukaryotes are generally larger and more complex
  and contain a nucleus and other organelles

Prokaryotic cell
Eukaryotic cell
Nucleoid region
Nucleus
Organelles
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Flow of Genetic Information
DNA RNA PROTEIN
- regulates growth and development - responsible
for the diversity of life
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• Diversity of Life can be Categorized
• Scientists have identified roughly 2 million
  extant species (many more now extinct)
• Classification of species into a hierarchy of
  increasingly broad groups based on common
  characteristics called TAXONOMY
• structured view of organisms to better understand
  an overwhelming amount of biological information
• helps us understand evolutionary history of a
  species or group of species

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HISTORY OF TAXONOMY

• Greek philosopher Aristotle (2,000 years ago )
• Designated organisms as Plant or Animal
• These further classified based on where they live
  (animals) or physical differences (plants)
• Carols Linnaeus (1700s)
• a system of groups called TAXA (singular taxon)
• based on structural similarities (MORPHOLOGY)

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Linnaean Classification System

• Hierarchical classification
• Domain gt Kingdom gt Phylum gt Class gt Order gt
  Family gt Genus gt species
• Two-part (binomial) species naming system
• 1st word Genus (small group of related
  organisms)
• 2nd word species identifier
• Latin for Genus and species names
• Genus is CAPITALIZED
• Genus and species are italicized or underlined.

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Felis catus
Species
Felis
Genus
Felidae
Family
Carnivora
Order
Mammalia
Class
Chordata
Phylum
Animalia
Kingdom
Eukarya
Domain
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Many different ways to define a species

• Biological Species Concept
• a population or group of populations that
  have the potential to interbreed and produce
  fertile offspring

• Some problems
• canids (dogs, wolves, coyotes)
• extinct species
• asexual reproduction

2. Morphological species concept
classification based on observable phenotypic
traits
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How are species maintained?
Reproductive Barriers keep closely related
species from interbreeding

• Can be either
• 1. Prezygotic- prevent mating or fertilization
• 2. Postzygotic- after zygotes are formed
  (hybridization)

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Prezygotic barriers

• temporal isolation
• some plants open flowers at different time of
  day

• mechanical isolation
• sex organs are not compatible

• behavioral isolation
• elaborate courtship rituals, pheromones, etc.

• habitat isolation
• live in same area but different habitats

• gametic isolation
• gametes cant unite to form a zygote, in
  mammals sperm
• cant survive in female of another species

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Postzygotic barriers

• hybrid inviability- genes are not compatible and
  the hybrids
• dont
  survive

• hybrid sterility- hybrids reach maturity but are
  sterile

• hybrid breakdown- 2nd generation hybrids
  inviable or sterile

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Six-Kingdom System

• MAJOR CELLULAR STRUCTURE
• METHODS OF OBTAINING NUTRIENTS
• METABOLISM

Based on
Protistans
Plants
Fungi
Animals
Eukaryotes
MONERA (previous Kingdom)
Eubacteria
Archaebacteria
Prokaryotes
Origin of life
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Three-Domain System

• Based on Ribosomal RNA
• To show common ancestry in distant past
• Living Things seem to fall into Three Broad
  Groups

Bacteria
Archaea
Eukarya
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Domain Eukarya
Domain Bacteria
Bacteria (multiple kingdoms)
Protists (multiple kingdoms)
Kingdom Plantae
Domain Archaea
Archaea (multiple kingdoms)
Kingdom Animalia
Kingdom Fungi
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Kingdom ARCHAEBACTERIA

• UNICELLULAR PROKARYOTES
• Cell Membranes
• Biochemistry
• Genetic Properties

Differ from ALL Other Kinds of Life

• - Autotrophic types (chemosynthetic)
• Heterotrophic types
• - Some inhabit HARSH ENVIRONMENTS
• (ex) Sulfurous Hot Springs

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Kingdom EUBACTERIA

• UNICELLULAR PROKARYOTES
• - Autotrophic types (photosynthetic)
• - Heterotrophic types
• (ex) Disease-Causing Bacteria
• tooth decay
• food poisoning

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Kingdom FUNGI

• EUKARYOTES
• most are MULTICELLULAR
• HETEROTROPHIC
• RELEASE DIGESTIVE ENZYMES
• Then absorb food
• DECOMPOSERS or PARASITES
• Includes molds, mushrooms, yeast
• lichen (mycobiont photobiont associations)

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Kingdom PLANTAE

• EUKARYOTES
• MULTICELLULAR
• - Autotrophic types (photosynthetic)
• - Heterotrophic types (i.e. venus flytrap)
• Includes mosses, ferns, flowering plants,
  cone-bearing plants

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Pitcher plants and Sundews (heterotrophic bog
plants in Maine)
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Kingdom ANIMALIA

• EUKARYOTES
• MULTICELLULAR
• HETEROTROPHIC
• Most have locomotion, some are sessile
• Includes sponges, coral, invertebrates, birds,
  fish, reptiles, amphibians, mammals

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Kingdom PROTISTA

• MORE What They Are Not than What They Are !
• Includes ALL Eukaryotes NOT Plants, Animal, or
  Fungi
• Many scientists want to spit into
  multiple Kingdoms
• Includes Amoeba, paramecium, phytoplankton, and
  seaweed
• (1) Single-celled PROTOZOA (animal-like
  heterotrophs)
• (2) Single-celled ALGAE (plant-like
  photosynthetic)
• (3) Multi-celled ALGAE (plant-like
  photosynthetic)

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Nothing in biology makes sense except in
light of evolution
Theodosius Dobzhansky (1900-1975)
EVOLUTION explains the unity and diversity of
life NOT the ORIGIN of LIFE!!!
Hypothesized steps in origin of life

1. Abiotic synthesis of macromolecules ?
2. Formation of protobionts ?
3. Self-replicating RNA ribozymes ?

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Jean Baptiste Lamarck (early idea of
evolution) - Lamarckian Evolution - Adaptation
from use and disuse - Inheritance of acquired
characteristics
INCORRECT !!

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• Charles Darwin proposed the
• theory of evolution by NATURAL SELECTION
• (1) Suggests that all life has a COMMON ORIGIN
• Does NOT explain the origin of
  life !!
• (2) ADAPTATION or descent with modification
• Explains ONLY the diversity of
  life !!
• occurs as heritable variations are exposed to
  environmental factors that favor the reproductive
  success of some individuals over others
• Species may change over time
• New species may arise

BIOLOGICAL ADAPTATION ? ACCLIMATION
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Populations are units of evolution

• 1) heritable variation in population
• 2) natural selection against some forms
• 3) differential reproduction
• 4) change in heritable variation of population

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Population with varied inherited traits
Elimination of individuals with certain traits
Reproduction of survivors
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1831 HMS Beagle Darwin visits the Galapagos
Noticed different adaptations among similar
species
Great Britain
Europe
Asia
North America
ATLANTIC OCEAN
PACIFIC OCEAN
Africa
PACIFIC OCEAN
Equator
South America
The Galápagos Islands
PACIFIC OCEAN
Pinta
Genovesa
Australia
Marchena
Equator
Cape of Good Hope
Andes
Santiago
Daphne Islands
Pinzón
Fernandina
Tasmania
Cape Horn
New Zealand
Santa Cruz
Isabela
Santa Fe
San Cristobal
Tierra del Fuego
0
40 km
Florenza
Española
0
40 miles
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Modes of Selection

• Directional
• an increase in one particular phenotype
• away from average
• Diversifying (or Disruptive)
• an increase in two different phenotypes
• away from average
• Stabilizing
• An increase in the average phenotype while
• a decrease in all other phenotypes

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Original population
Frequency of individuals
Phenotypes (fur color)
Original population
Evolved population
Stabilizing selection
Directional selection
Disruptive selection
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Natural Selection
Chromosome with gene conferring resistance to
pesticide
Pesticide application
Additional applications of the same pesticide
will be less effective, and the frequency
of resistant insects in the population will grow
Survivor
similar to how bacteria can become ANTIBIOTIC
RESISTANT
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Natural Selection (ex) Change in coloration of
pepper moths due to the rise of industrial
pollution in England
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Natural Selection (ex) development of camouflage
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Natural Selection (ex) development of mimicry
Poisonous monarch (above) mimicked by
non-poisonous viceroy (below)
Artificial Selection Trait selection by humans
resulting in domestication
- many vegetables
- many animal breeds
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• Sexual selection may produce sexual dimorphism
• Sexual dimorphism
• The distinction in appearance between males and
  females of a species
• Sexual selection
• The determining of "who mates with whom"
• Leads to the evolution of secondary sexual
  characteristics that may give individuals an
  advantage in mating

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• Selection does not create perfect organisms
• Selection can only act on existing variations
• Adaptations are often compromises
• Chance and natural selection interact
• Environment and selection pressure change
• Evidence for Evolution
• 1. fossils
• 2. anatomy
• 3. embryology
• 4. molecular biology
• 5. biogeography

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Evidence for Evolution Fossil Record
RECENT
(ex) Fossil horses - show series of changes in
feet and teeth
Equus
Hippidion and other genera
PLEISTOCENE
Nannippus
Pliohippus
Neohipparion
Hipparion
PLIOCENE
transitional forms with geological reference in
many lineages !!
Megahippus
Sinohippus
Callippus
Archaeohippus
Merychippus
MIOCENE
Hypohippus
Anchitherium
Parahippus
Miohippus
OLIGOCENE
Mesohippus
Paleotherium
Epihippus
Propalaeotherium
Pachynolophus
Orohippus
EOCENE
Grazers
Hyracotherium
Browsers
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• VESTIGIAL STRUCTURES
• apparently useless features
• - once useful to an ancestor
• - an organism may share close ancestor with
  another organism with a functional version of the
  structure

Pakicetus (terrestrial)
Rhodocetus (predominantly aquatic)
Pelvis and hind limb
Dorudon (fully aquatic)
(ex) fossil from Basilosaurus, an extinct whale
with hind legs
Pelvis and hind limb
Balaena (recent whale ancestor)
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A Skull of Homo erectus
B Ammonite casts
C Dinosaur tracks
D
Fossilized organic matter of a leaf
E Insect in amber
F Ice Man
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Evidence for Evolution Comparative Anatomy

• Related organisms share a similar body plan
• (ex) Backbone, rib cage, appendage bones and
• arrangement of internal organs in
  fish, amphibian,
• reptiles, birds and mammals

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Evidence for Evolution Comparative Embryology
Early embryos of related organisms are very
similar (ex) all vertebrate embryos
develop gill-like structures
Pharyngeal pouches
Post-anal tail
Human embryo
Chick embryo
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Evidence for Evolution Molecular Biology

• Universality of the genetic code
• Similarity of nucleic acid and amino acid
  sequences

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Evidence for Evolution Biogeography

• organisms evolve to adapt to their environment
• (ex) Darwins finches
• (ex) CONVERGENT EVOLUTION (sugar glider / flying
  squirrel)

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Systematics the study of biological
diversity in an evolutionary context
hierarchical classification reflecting
evolutionary relationships

• Taxonomy
• the naming and classification of species
• Phylogeny
• the evolutionary history of a species or group of
  species
• Phylogenies are HYPOTHESES to be tested
  against available data
• Phylogeny is debated and Taxonomy
  constantly changes
• as new
  evidence is discovered

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Canis lupus
Felis catus
Mephitis mephitis
Lutra lutra
Canis familiaris
Species
(domestic cat)
(striped skunk)
(domestic dog)
(European otter)
(wolf)
Felis
Genus
Lutra
Mephitis
Canis
Family
Mustelidae
Felidae
Canidae
Order
Carnivora
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HOMOLOGOUS FEATURES

• Features which look and function differently BUT
• 1. have similar anatomies
• 2. have similar embryological origins
• (ex) LIMBS of VERTEBRATES
• Changes in overall form and function
  can be
• modified through time

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Similarity due to common ancestry Different
functions due to adaptation
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ANALOGOUS FEATURES

• Features which share similar functions and may
  look similar BUT
• 1. have different anatomies
• 2. have different embryological origins
• (ex) WINGS of BIRDS and INSECTS
• Wings evolved independently in more
  recent
• ancestors of each organism

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CLADISTICS

• simple system of phylogenetic classification
• Based on Shared Derived Characters
• feature that apparently evolved only within the
  group under consideration
• (example)
• Most animals dont have feathers
• Birds are the only animals that have feathers
• Can assume that FEATHERS were derived within the
  BIRD GROUP
• Used to establish the simplest (most
  parsimonious) explanation of groupings (clades)

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Using Shared Derived Characters to create a
CLADOGRAM (phylogenetic tree)