Ecology as Science
How does the scientific method work?
“The Happy Bear”
Observation
Question
Research
Guess (Hypothesis - an educated guess)
Experiment
Analyze Data (commonly use stats to infer significant results)
Conclusion (repeatable) OR back to Question
Ecologists evaluate competing hypotheses about natural systems with… (3 things)
experiments, observations, and models
Methods to answer questions about the natural world: (4)
- Observational Studies
- Experiments in the field (only so much you can control)
- i.e. barnacles exposed/unexposed to predators; leaves labelled with isotope of carbon (which acts as a dye) - Controlled lab experiments (greenhouse)
- Quantitative Models
Ecological Experiments (hierarchy)
lab experiments, small scale field experiments, large scale ecosystem experiments (to largest spatial scale and longest temporal scale)
i.e. ancient stores of carbon ‘burped’ into the atmosphere
Experimental Design (3 steps)
- Replicate—perform each treatment
more than once. - Assign treatments at random.
- Statistical analysis is used to determine
significant effects.
The Two Key Rs
Replicate and Randomize
Critical C
Control
i.e. injecting poison and water into pike muscle tissue (ensures the injection, the needle itself does not effect the results)
Purpose for an experimental control
Controls are used to account for anything that may potentially affect results
Experiments have 3 attributes: No experiment can capture all three
*Hint: GRP
- Generality (large-scale studies)
- Realism (field experiments)
- Precision (lab experiments)
Case Study: Deformity and Decline in Amphibian Populations
High incidence of
deformities in
amphibians
Declining populations
of amphibians
worldwide
Case Study: Why Amphibians?
- live on land and water
- permeable skin
*making it a sensitive species = good bio indicators (like fungus and lichen)
Case Study:
A controlled experiment:
Tree frog eggs were exposed to Ribeiroia
parasites in the lab.
Four treatments: 0 (the control group), 16,
32, or 48 Ribeiroia parasites.
Case Study:
A field experiment:
Six ponds, three with pesticide
contamination.
Six cages in each pond, three with mesh
size that allowed parasite to enter.
Case Study:
Hypothesis: Pesticides decrease the
ability of frogs to resist infection by
parasites.
Studies have suggested that no single
factor can explain decline of amphibian
populations.
The declines seem to be caused by
complex factors that often act together
and may vary from place to place.
Complex Causation
Hatch and Blaustein (2003) studied the
effects of UV light and nitrate on Pacific
tree frog tadpoles.
UV: higher at high elevations
Nitrate: from farms
Case Study: Cysts
Cysts mess up formation of limbs
- become easy prey
- passed out in bird feces
Glass bead mimicked the effect of a cyst
