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BIOL1020H Week 2: Lectures 1 & 2
Outline Biology: a defini@on Scien@fic reasoning in biology: a short history Hypothesis tes@ng Methods of study A case study in scien@fic inquiry
• Biology is the scientific study of life • Biologists ask questions such as
– How does a single cell develop into an organism? – How does the human mind work? – How do living things interact in communities?
• Life defies a simple, one-sentence definition • Life is recognized by what living things do
Systems biology: scaling up from the results of reduc@onist inves@ga@ons
The approach that a_empts to model the dynamic behaviour of the whole biological system based on the study of the interac@ons among the system’s parts. For example: how might increasing a crop’s water supply affect the process of storage of molecules essen@al for human nutri@on
2. Francis Bacon (1561‐1626) Father of Induc@ve Reasoning Bacon’s induc@ve approach included ‘the careful observa)on of nature with a systema)c accumula)on of data to draw upon’. New natural ‘laws’ (or descrip@ons of pa_ern) were then created based on the knowledge of par@cular findings through ‘tes)ng and experimenta)on to determine if they were consistent with the observa)ons from nature.’
Inductive Reasoning • Inductive reasoning draws conclusions through the
logical process of induction • Repeating specific observations can lead to important
generalizations – Example 1. “the sun always rises in the east” – Example 2. The water at the beach has always been about 24 degrees in July. It is July. The water will be about 24 degrees.
– Inductive reasoning goes from observations to conclusion
1. Iden@fy a broad problem statement 2. Define a problem statement 3. Develop hypotheses (best guess) (plus
[email protected] step that is not always, but should be included in these steps!)
4. Determine measures 5. Data collec@on 6. Data analysis 7. Interpreta@on of data (e.g., do data fit with
your hypotheses and predic@ons?)
Do you learn more if you support or reject an hypothesis??
• All species of tree die. (Support hypothesis). This could lead to trying to figure out what general climate or atmospheric event might cause tree death)
• Only one species of tree die. (Reject hypothesis). This observa@on leads to the next hypothesis that there is a species‐specific agent that is killing the tree species.
• You can proceed just as quickly when you reject your ini@al hypothesis as if it is supported!
From www.undsci.berkeley.edu
DDE concentra@ons in faeces (guano) coincided with ini@al popula@on declines in
Chimney Swij
From www.undsci.berkeley.edu
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Migration routes and wintering grounds of three northern wheatears breeding in Alaskan (AK) and one in the eastern Canadian Arctic (CN; grey dot, breeding area, blue, autumn migration,
orange, spring migration, dashed lines indicate uncertainty in migration...
Bairlein F et al. Biol. Lett. doi:10.1098/rsbl.2011.1223
Darwin used mostly observa@ons, also ar@ficial breeding experiments. Most early biologists (also called natural
philosophers) were ardent naturalists
What IS known about Polar Bears to understand link with climate? • Climatology • Bear physiology • Bear popula@on biology • Bear systema@cs • Winter behaviour • Habitat selec@on • Sex roles and sex ra@os • Reproduc@ve biology • Geomorphology • Diet • Nutri@on • Responses to environmental varia@on (including both human and natural)
• In other words…. We need to understand their natural (or life) history…
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You will need to know something about your study organism!
Understanding the interac@on between a species and its environment has been termed the study of ‘autecology’ “Autecology, also called Species Ecology, is the study of the interac@ons of an individual organism or a single species with the living and nonliving factors of its environment. Autecology is primarily experimental and deals with easily measured variables such as light, humidity, and available nutrients in an effort to understand the needs, life history, and behaviour of the organism or species.” Encyclopedia Britannica, online. Note: You are NOT doing ‘Synecology’, the study of the structure and func@on of ecological communi@es.
Types of Data • Data are recorded observations or items of
information; these fall into two categories – Qualitative data, or descriptions rather than
measurements • For example, Jane Goodall’s observations of
chimpanzee behavior – Quantitative data, or recorded measurements,
which are often organized into tables and graphs and because they are often variable, analysed with statistics! Also comes in various forms.
Counts (e.g., number of flowers, which can then be expressed as percentages) Con@nuous data (e.g., heights, masses) Binary responses (e.g., yes/no; presence/absence)
A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations
• Many poisonous species are brightly colored, which warns potential predators
• Batesian mimics are harmless species that closely resemble poisonous species
• Henry Bates (1861) hypothesized that this mimicry evolved in harmless species as an evolutionary adaptation that reduces their chances of being eaten
• This hypothesis was tested with the venomous eastern coral snake (Micrurus fulvius) and its mimic the nonvenomous scarlet kingsnake (Lampropeltis elapsoides)
• Both species live in the Carolinas, but the kingsnake is also found in regions without venomous coral snakes
• If predators inherit a (local) avoidance of the coral snake’s coloration, then the colorful kingsnake will be attacked less often in the regions where coral snakes are present
• After four weeks, the scientists retrieved the artificial snakes and counted bite or claw marks
• The data fit the predictions of the mimicry hypothesis: the ringed snakes were attacked less frequently in the geographic region where coral snakes were found
• Why? Because these results could have occurred due to chance alone.
• We use sta@s@cs to determine whether the results are probable due to chance alone.
“The mean propor@on of ringed replicas a_acked was significantly greater in allopatry (0.654 ± 0.107) than in sympatry (0.083 ± 0.116; P= 0.009, 2‐tailed Wilcoxon two‐group test).”
Experimental Controls and Repeatability • A controlled experiment compares an
experimental group (the artificial kingsnakes) with a control group (the artificial brown snakes)
• Ideally, only the variable of interest (the effect of coloration on the behavior of predators) differs between the control and experimental groups
• A controlled experiment means that control groups are used to cancel the effects of unwanted variables
• A controlled experiment does not mean that all unwanted variables are kept constant
• In science, observations and experimental results must be repeatable (but they are often NOT repeated, unless there is a very strong financial or medical consequence to the research).
• Coopera@on makes science proceed more rapidly (e.g., mul@ple labs looking for Ebola vaccine)
• Science without communica@on is not science!
Nega@ve results are PROBABLY underrepresented in the published literature (and ojen sit in electronic files for years or in unpublished theses). Model organisms in Ecology and
In Conserva@on Biology we have our own ‘model organisms’ (also called
‘Flagship species’)
Atelopis varius (Harlequin Frog) Affected by airborne toxins, decline in habitat, change in climate, breathes through skin so sensi@ve to air quality.
Loxodonta africana (African Elephant) And (unfortunately) many more….
Second case study: What pollinates arc@c plants? Start with an observa@onal study,
con@nue with a field experiment Hypothesis: Bees will be primary pollinator (because we know that they are the most important plant pollinators on earth) Method: Observe plants from a distance to determine what hangs out on the plant’s flowers. Lin (2013). M.Sc. Thesis, Trent University. Conducted his research in Ivvavik Na@onal Park, Yukon
Test organism (not necessarily a ‘model’ organism):
Buffaloberry, Soapberry et al. (Sheperdia canadensis) Ivvavik Na@onal Park, Yukon
Visitors to arc@c Buffaloberry over 40 hours of observa@on
Did we accept or reject our hypothesis?
Bees will be primary pollinator (because we know that they are the most important plant pollinators on earth)
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Which of ants or flies pollinate arc@c plants (or neither, or both)? Conduct
field experiment Hypothesis: Ants will pollinate the plants because they were more numerous and not as affected by high arc@c winds Test: Exclude ants, exclude bees and flies, control
Results from two different sites in the park (replicated!): fruits were produced only (almost) when flies were able to
visit!
Did we accept or reject our hypothesis?
Ants will pollinate the plants because they were more numerous in our observa@onal study on the plants and not as affected by high arc@c winds
Plant‐animal interac@ons, niche theory and more next week!
Manatee (Trichechus manatus) feeding on hydrilla, an introduced species.