Transcript biological questions - School of Biological Sciences

WHAT IS SCIENCE?
• science (Latin “to know”); way of knowing
• process for describing, understanding &
explaining natural world
• science is inquiry: search for information
& understanding
• what are the foundations for scientific
inquiry?; what is the scientific method?
• characterization & hypothetico-deductive
reasoning
• “if...then” logic
WHAT IS SCIENCE?
• #1: characterize a phenomenon
– careful observations; senses, tools
– analysis of data; qualitative, quantitative
– inductive reasoning: generalizations from a
large series of observations
• Fig. 1.23: Jane Goodall’s field notebook
WHAT IS SCIENCE?
• #2: formulate a hypothesis
– causes & explanations
• #3: deduce a prediction
• #4: test the prediction
• if prediction upheld, deduce & test more
predictions
WHAT IS SCIENCE?
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if prediction not upheld:
1) determine if test performed correctly
2) consider other confounding factors
3) revise hypothesis
4) develop a new hypothesis
Fig. 1.24
HYPOTHESIS
• hypothesis: explanatory statement based on
natural (not supernatural) causes; testable
– dead batteries or bad bulb vs. ghost
• prediction: what should observe if hypothesis
is good explanation
• test: observation, experiment; field or lab
• if prediction supported, hypothesis robust
– explanatory power; increased knowledge
• if not supported (& ruled out mistakes,
confounding factors)
– falsified; increased knowledge
• mistake: batteries in backward
• confounding factors: contacts rusted
VALUE OF SCIENCE
• ultimately independent of intuition,
opinion, emotion, faith
• rigorous, self-correcting
• rigorous:
• 1) need evidence to support hypothesis;
in form of supported predictions
• 2) competing hypotheses evaluated
based on evidence, not opinion
VALUE OF SCIENCE
• self-correcting:
• 1) peer review (others evaluate)
– peer-reviewed primary literature
• paper: abstract, introduction, methods, results,
discussion, literature cited
– journal research article (paper) vs.
magazine article
• 2) replication (others repeat obs/exp)
– verifiability
HYPOTHESIS
• confidence depends most on # of different
predictions tested
• as robustness increases, accepted as a good
natural explanation of phenomenon
• hypothesis NOT an opinion
• hypothesis with more successful tests of
different predictions is better
• "burden of proof” is on person with less
successfully tested competing hypothesis
• media mistakes in science reporting:
– competing hypotheses equal opinions
– always more than one scientific (vs. policy) side
THEORY
• theory: well-tested group of interrelated
hypotheses
– many robust hypotheses; large body of evidence
• germ (microbe) theory of disease; cell theory;
atomic theory; global climate disruption
theory
• theory of natural selection (evolutionary
change)
• broader explanatory statement
• confidence depends most on # of different
predictions tested; has high robustness
(explanatory power)
• theory NOT an opinion
• “just a theory” not accurate in science;
confused with vernacular usage
BIOLOGICAL QUESTIONS
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three classes of questions:
what questions
how questions
why questions
WHAT QUESTIONS
• characterization (= description)
• discovery (= descriptive) science
• focused observations (data)
– field (nature), laboratory
– qualitative (Goodall) or quantitative
• foundation for constructing hypotheses
(explanations)
– focused/precise observations (196 lab)
• hypothesis based on poor characterization
has no explanatory power
WHAT QUESTIONS
• what do North Temperate Zone birds do
to survive the winter?
• most migrate south in fall
WHAT QUESTIONS
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characterize patterns of migration
one pattern: major flyways
spatial, temporal components
West Nile virus
www.cdc.gov/ncidod/dvbid/westnile/cycle.htm
HOW QUESTIONS
• how do birds migrate?
• functional processes
• hypothesis: geomagnetic field for
orientation
• prediction: if change direction of
geomagnetic field, then bird will change
direction of migratory movement
• artificial magnetic field experiment
– confounding factor controlled: sun
orientation
WHY QUESTIONS
• why do birds migrate south in the fall?
• North Temperate Zone bias
• why do birds migrate north in the
spring?
• Tropical Zone perspective
• evolutionary processes
• history matters in biology; evolutionary
history
WHY QUESTIONS
• hypothesis: seasonally abundant food source
• general prediction: if common ancestor of
taxon originated in tropics, then center of
evolutionary origin should be in tropics
• specific prediction: if center of origin is in
tropics, then highest biodiversity of taxon
should be in the tropics
• taxa: tanagers, orioles, flycatchers
• Americas: many migratory birds belong to
groups with highest biodiversity in tropics
WHAT/HOW QUESTIONS
• what questions: focused observations in
field/lab
– characterization (discovery)
• how questions:
– current function of characters of organisms
determined from focused observations
– characters: morphological, behavioral, ecological,
physiological, molecular
• experimental approach
– manipulation of characters in field/lab
WHY QUESTIONS
• evolutionary history of characters
– history of form/function; natural selection forces
– explain the present by reconstructing the past
• historical approach
– focused obs in field/lab based on h-d thinking
– comparative studies in field/lab
– reconstruct past processes/events from present
patterns
LANGUAGE OF SCIENCE
• precision needed; new phenomena
• vocabulary learned through word roots;
Latin, Greek
• arthropod
– arthr means jointed in Greek
– pod means foot in Greek
• arthritis: itis = inflammation (G)
• podiatrist: iatrist = physician (G)
• dictionary
HIERARCHY OF LIFE
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levels of biological organization (Fig. 1.4)
biomolecular level (e.g. chlorophyll)
organelle level (e.g. chloroplast)
cellular level (cell: most basic living unit)
– e.g. photosynthetic cell
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now at life: Fig. 1.3 has basic properties
tissue level (e.g. leaf epidermis)
organ level (e.g. leaf)
organ system level
HIERARCHY OF LIFE
• organism level (unicellular, multicellular)
• animal example
– (e.g. DNA, cardiac cell nucleus, cardiac muscle
cell, cardiac muscle tissue, heart, circulatory
system)
• population level (local group of orgs of same species)
• species level (groups of interbreeding pops)
• community level (groups of species in a local area)
• ecosystem level (communities + physical
environment)
• biosphere level (all Earth’s ecosystems)
• Fig. 52.2: types of ecology
HIERARCHY OF LIFE
• 1) emergent properties: each level more
than sum of lower level
– "more than the sum of their parts"
– can't understand organism fully just by
sequencing DNA
• 2) structure & function correlated at
each level
• bird adaptations for flight
– bones, nerves, muscles (Fig. 1.6)
Fig. 1-6
(a) Wings
(b) Bones
Infoldings of
membrane
Mitochondrion
100 µm
(c) Neurons
0.5 µm
(d) Mitochondria
HIERARCHY OF LIFE
• biologists study all levels
• Lyme disease (Fig. 27.21): emerging
infectious disease
• emerging:
– 1) new disease, or
– 2) old disease now more widespread, or
– 3) old disease now more problematic
• zoonotic: transmission from animals to
humans
LYME DISEASE
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biology of Lyme disease
molecular biology, genetics, cell biology
ignores other levels & emergent properties
ecology, systematics, evolution
major applications
– medicine (evolutionary medicine), agriculture
(agroecosystems), conservation
– http://chge.med.harvard.edu
– www.landinstitute.org
– www.conservationmedicine.org
• ecology of Lyme disease
• public health problems can be ecological
problems
LYME DISEASE
• the players (what)
– spirochete bacterium (Borrelia burgdorferi)
– mouse, tick, deer, oaks
• the processes (how)
– symbiosis: parasitism
– life cycles
– masting
LYME DISEASE
• parasitism: parasite, host, often a vector
• host for Borrelia:
white-footed mouse (interior forest)
• vector for Borrelia: deer tick
• hosts for deer tick:
1) white-footed mouse
2) white-tailed deer (ecotone)
• both good tick hosts at different life stages
• life cycle with stages
LYME DISEASE
• tick egg hatches, larval stage (uninfected)
searches for a vertebrate host
• if an infected white-footed mouse, gets
Borrelia through blood meal
• at nymph stage, tick searches for another
vertebrate host
• if another white-footed mouse, transmission
• at adult stage feeds on white-tailed deer,
mates, leaves to lay uninfected eggs
• if infected nymph (or adult) feeds on human,
Borrelia can be transmitted and human can
get Lyme disease
www.cdc.gov/ncidod/dvbid/lyme/ld_transmission.htm
LYME DISEASE
• important ecological factors
– mouse abundance
– deer abundance
– mouse-deer proximity (spatial)
• all controlled by food supply: acorns
• masting: every 2-5 years (temporal
component) oak trees produce large
amount acorns
• why?
LYME DISEASE
• masting causes ecological chain reaction
• more acorns
• more mice
– more Borrelia
• more deer
• more mouse/deer proximity
• more ticks for 2 reasons
– more hosts, easier movement between hosts
• higher risk Lyme disease
• why an emerging disease?
FOREST FRAGMENTATION
• "Show me almost any [emerging] infectious disease,
and I'll show you an environmental change brought
about by humans."-Dr. Peter Daszak, Consortium for Conservation Medicine
• humans cut forests, leave fragments
• white-footed mouse tolerant of fragmentation
• but other mammals declines, so overall
mammal biodiversity declines
• reduction of a process: dilution effect
• many species dilute the effect of disease
prevalence and transmission
www.ecostudies.org/people_sci_ostfeld_dilution_effect.html
www.ecostudies.org/people_sci_ostfeld_dilution_effect.html
FOREST FRAGMENTATION
• sprawling development, other damage
to forest ecosystems = increase in
likelihood of Lyme disease
• decline of biodiversity has medical
impacts
• conservation biology & medicine closely
linked = conservation medicine
• dilution effect operates with West Nile
virus too
BIODIVERSITY
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unity & diversity
unity: all life linked by evolution; "kinship of all life"
human lung clearance and Paramecium motion
Fig. 42.24: human respiratory organ system includes
cilia
• Fig. 28.11: Paramecium move using cilia
• both part of taxon Eukarya (eukaryotes); share a
common ancestor (Fig. 28.3)
• cilia structure (form) same even though function
different; functional shift; Fig. 1.16
BIODIVERSITY
• diversity: adaptations reflect differences in life
histories
• "descent with modification"
• natural selection critical to understand
character adaptations
• main mechanism of evolution (evolutionary
change & diversification)
• hierarchy of biodiversity (3 basic levels)
• genetic biodiversity
• species biodiversity
• ecosystem biodiversity
GENETIC BIODIVERSITY
• genetic variation among individuals of a
single species (singular, plural)
– individuals make up pops
– pops make up species
• within-population genetic biodiversity
• among-population genetic biodiversity
– geographic variation
SPECIES BIODIVERSITY
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all the species on Earth
around 1.8 million described
total number between 10-100 million
this “what” question still a mystery
196 surveys components known now
classification a dynamic science:
taxonomy, systematics (Fig. 1.14)
ECOSYSTEM BIODIVERSITY
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all the ecosystems on Earth (biosphere)
species not randomly distributed
similar ecosystems grouped into biomes
what terrestrial biomes are the ecosystems of
Illinois part of?
• temperate broadleaf forest biome (Fig. 52.21)
• eastern deciduous forest ecosystem (e.g.
Shawnee National Forest); 40%
ILLINOIS
• temperate grassland biome (Fig. 52.21)
• tallgrass prairie ecosystem; 60%
ILLINOIS
• original 22,000,000 acres reduced to
2,200 acres
• lost many ecosystem free services
• restoration ecology