General Ecology BIOL 3700 – Lecture Notes
Lecture 1
Lecture 1: Introduction to Ecology
Outline
 What is ecology?
 Why is ecology difficult to study?
 Why should we study ecology?
 What is good science?
 Working definitions of ecology
The organization of living things: levels of biology [we will use these over and over]
• Biosphere: the spatial extent of life on earth
• Ecosystem: interaction between organisms and the physical/abiotic environment
• Community: group of species living in the same area… emphasis on species
interactions (predation, competition, mutualism)
• Population: group of individuals living in the same area
• Individual
The organization of living things: levels of biology – you should be able to describe a
species place in the biosphere across all ecological levels above
Individual level
Ecologists ask, “What factors affect the survival and reproduction of individuals?”
-ex. Temperature-dependent sex determination in “reptiles” (turtles, crocs, alligators)
Population level
Ecologists ask, “What causes populations to fluctuate?”
Community level: species interactions
Ecologists ask, “What factors maintain diversity?” “What causes diversity to vary over
space and time?”
 Rober Helmer MacArthur (1930-1972), Princeton University
 MacArthur and warbler feeding zones
 “How do so many species of warblers coexist?”
1
General Ecology BIOL 3700 – Lecture Notes
Lecture 1
Ecosystem level
Ecologists ask, “What maintains productivity and causes it to vary across space and time?”
and “How does energy (e.g. solar radiation) flow through an ecosystem?”
“How fast do nutrients cycle?”
 Nalini M. Nadkarni (1954–present) and tropical rainforests of Costa Rica
• “How can tropical forests maintain such high productivity when the soils are
nutrient poor?”
The biosphere: life on earth
Ecologists ask questions like, “What role do concentrations of atmospheric CO2 play in the
regulation of global temperatures and climate?”
Origins of the word “ecology”
Henry David Thoreau (1817-1862)
 Skilled naturalist; did not coin term; misinterpretation of his notebooks
Ernst Haeckel (1866), coined term
 oikos – Greek for “habitat or home”
 logos – Greek for the study of something (where we get English suffix “-ology” from)
 Ernst Haeckel (1834-1919)
What isn’t ecology?
Environmentalism = a social and political belief system, philosophy, and movement
advocating the improvement and preservation of healthy ecosystems.
However, ecologists often adopt an environmentalist stance because of their studies of
nature.
Why is ecology so difficult to study? Complexity
Our understanding can be limited by the scales at which we view the world
Observational bias
2
General Ecology BIOL 3700 – Lecture Notes
Lecture 1
Our senses can be fooled
Note the following slides
Scale restricts perception
The size of the window through which we view the world and how long and how
frequently we look will determine what we see…the relationships, patterns &
processes that seem important…
How does scale affect our understanding of other species?
 Each species will view the world on unique spatial & temporal scales based on
restrictions: size, & mobility
o Beetles, warblers, and hawks
 We must see the world from their perspectives.
Example
Dodson et al. (2000): humped-shape relationship between species richness and
nutrient availability (N&P) in 21 Michigan lakes…
But scale dictates the species richness-diversity relationship in lakes – Chase &
Leibold (2002), Nature
 You get the expected positive linear relationship at the regional scale, sampling
multiple lakes in different watersheds
What makes humans unique?
 We can view the world at various spatial and temporal scales.
 But we must be careful…
Beware of observational biases! [several slides]
Cultural biases? [Speed Cooking video]
Cultural biases?
People of different cultures may see the natural world in very different ways, e.g. …
 some people worship cows and rats
 some people eat live animals
 Humans are a diverse, sometimes cruel species
We must be aware of how our culture & background affect how we think.
What are your cultural biases?!
Why study ecology? Why be an ecologist?
 “Most ecologists develop a ‘love’ for their organism, for the environment, and for
asking questions about their system.” – Mark Pyron
Why study ecology?
What is the value of everything, i.e. the value of healthy natural ecosystems?
3
General Ecology BIOL 3700 – Lecture Notes
•
Lecture 1
What would it cost if the free services associated with natural ecosystems were
suddenly removed from the Earth?
Why study ecology?
 Ecosystem services (clean water)
 Food production (pollination & nitrogen)
 Preservation of biodiversity
o Medicine
 Political issues
 Stewardship
 Human needs
 Why study ecology?
Why study ecology?
We require healthy natural ecosystems (psychological, physiological and recreational
needs)
Why study ecology?
The economics of ecosystem services – economic value
Costanza et al. (1997) Nature 387:253
• From their Abstract:
– “For the entire biosphere, the value (most of which is outside the market) is
estimated to be in the range of US$ 16-54 trillion (1012) per year, with an
average of US$ 33 trillion per year. Because of the nature of the
uncertainties, this must be considered a minimum estimate. Global gross
national product total is around US$ 18 trillion per year.”
– See Ecological Economics 25:1-142 (1998) for additional information.
Why study ecology?
Assessing value depends on our philosophical foundation… What is your perspective?
• Are there over-arching moral ideals that can guide decisions on the value of a
sustainable environment for future generations?
What are the ultimate goals of science?
 Understanding
 Prediction
 Application
What are the challenges to achieving these goals?
 Chance/stochasticity
 Human bias
o Cultural
o Observational
 Complexity
4
General Ecology BIOL 3700 – Lecture Notes
Lecture 1
o Many patterns are produced by multiple processes & factors, or
“multicausality”
o These can interact in complex ways
What is good science?
Discuss.
What is good science?
 An objective, systematic method for detecting patterns and the processes that
produce patterns.
o Causation is the goal because it allows prediction.
 Based on observations that produce a good question.
 When possible, it should be repeatable/verifiable.
 Self-correcting… it is a learning process
What is a “process”?
Any force that produces or causes a pattern
 Examples:
o Infectious agents causing disease
o Hormones causing growth and development
o Predator consumption causing prey populations to cycle
Processes explain how and why patterns occur… they show causation.
There are 4 traditions on how to do science:
1. The empirical/descriptive/observational tradition:
o Scientists collect descriptive data in the field (e.g. Does diversity vary between
springs?).
o They use statistical techniques to determine which variables are correlated with the
response variable.
o They use data collected at a specific time and place, thus, the generality of the
results are contingent on that time and place. Does that time and place represent all
times and places?
2. The theoretical tradition:
o Scientists use math models to represent ecological processes symbolically (e.g.
competition coefficients and the functional and numerical response of predators to
analyze stability properties of species interactions).
o No empirical data is used.
o They are overly simplified representations of nature designed to identify sweeping
generalities that are not contingent on the time and place of empirical models.
3. The simulation tradition:
o Scientists use math models to represent ecological processes but the parameters
(e.g. competition coefficients) are not represented symbolically, they are based on
empirical/descriptive data.
o They are less of a simplification of nature. Our best effort to overcome complexity.
All of the parameters that scientists can think of are included in a massive model
5
General Ecology BIOL 3700 – Lecture Notes
Lecture 1
that requires high speed computers for analysis. There are separate complex
algorithms that represent each process that could effect the response variable (e.g.
the concentration of CO2 in the atmosphere). These are attempts to represent
nature in all its complexity.
o The model provides a simulation showing how the response variable changes as
parameters that control the response variable vary over time. Models that simulate
climate change are included here.
4. The experimental tradition:
o Experiments manipulate 1 or 2 potential factors (ozone levels) that may control the
response variable (atmospheric CO2) while keeping all else in a natural state.
o Cause and effect can be determined because of the basics of experimental design:
o Controls, replication, randomization to reduce bias and uncertainty.
o Although this is a very powerful tool, experiments are limited by spatial extent,
temporal duration, and the number of factors that can be examined.
The scientific traditions… going deeper:
o Empirical/descriptive/observational studies, and
o Experiments
We will do some theoretical modeling to explore population growth and the effects of
competition and predation.
We will not try the simulation tradition.
What is an empirical/descriptive/observational study?
o A systematic method for detecting patterns.
o This is often how we formulate good questions to test experimentally.
o Good questions are designed to promote understanding and address society’s needs.
What is an experiment?
o A method to determine causation or the processes that produce patterns.
o Correlation is not causation
What are the basics of experiments?
The Concept is to keep everything the same/natural and manipulate the factor of interest.
Controls are set up with “normal” conditions without manipulating the factor of interest.
Treatments are conditions when we manipulate the factor of interest.
Experimental units are the physical entity that we manipulate.
Response variables are what we measure.
How do we avoid bias and reduce uncertainty?
Randomization – randomly assign a control or treatment to each experimental unit.
Replication – more replicates are better, but there are limitations.
Use a laboratory experiment.
Question: Can phosphorous increase the growth rate of green common bean plants
(Phaseolus vulgaris)?
o What is the hypothesis?
o What is the response variable?
6
General Ecology BIOL 3700 – Lecture Notes
o
o
o
o
o
o
o
Lecture 1
What is the experimental unit?
What is the control?
What is the treatment?
How would we replicate this study?
Why would we replicate this study?
How would we randomize this study?
Why would we randomize this study?
Use a field experiment.
Question: How does invertebrate diversity in riffles change with elevation in the upper
Provo River?
o Can you develop a good working hypothesis?
o What is the response variable?
o What is the sampling unit?
o What is the control?
o What is the treatment?
o How would we replicate this study?
o Why would we replicate this study?
o How would we randomize this study?
o Why would we randomize this study?
How do these two studies differ? What is the essence of an experiment?
Can science eliminate all uncertainty?
 No… but weight of evidence is key!!
 Strong support: evidence based on all 4 traditions and numerous independent
studies
 Cross-validation
 Necessary to reduce uncertainty to determine whether scientific knowledge is
sufficient to justify policies and decisions.
Many questions can’t be tested with experiments
Example:
Hypothesis: Bengal tiger cubs grow best in valleys of India where humans are absent.
Observation:
 Inverse relationship between tiger density and human density in valleys of India.
 Graph? Is this correlation or causation?
 Set up an experiment to test this hypothesis at the appropriate scale.
Panthera tigris tigris, IUCN 3.1 Endangered Species
The End of the Intro
Minute paper #1:
What were the two most important points in this lecture?
7