Welcome to
Principles of Ecology
What questions come to your mind?
How many bats live in this group?
Course Introduction
What is Ecology?
Ecology as a discipline is motivated by human efforts to
describe, understand, predict, and modify nature.
Contemporary ecology research aims to understand
the factors that shape where organisms live,
how their abundances change over time,
how interactions shape communities and ecosystems,
and how these are affected by global environmental change.
This course will introduce you to the questions that motivate the field of ecology, the approaches that ecologists take, and the implications of ecological research for societal challenges.
About me
“I am an ecologist, and I spend my time thinking about the origins, structure, maintenance, and consequences of diversity.”
Research focus: How are the above-ground dynamics of plant communities affected by below-ground microorganisms?
How to call me: Dr. Kandlikar (like “candy car”, but “candly-car”), or Dr. G, or Dr. K, or Gaurav (like… “gau-rav”)
Photo by Gaurav, of Tejon Ranch in southern California
Photo by Gaurav, of a forest canopy in south India
Appproaches to ecology
Find out more at gklab.org:
I want to get to know you!
- Please fill out the “Who’s in class” survey on Moodle!
How many bats live in this group?
How many bats live in this group?
Why is this simple question not very simple to answer?
Some complicating factors:
- Our brains are bad at processing big (or small) numbers
- Population size changes over time – so, when do we want to know?
- The bats don’t exist in a vacuum – how do interactions (with other organisms, with human decisions, etc.) shape this population?
Photo by Matej Spulak on Unsplash
Common themes in ecology
- Ecological systems are dynamic, meaning that their properties can change over time.
- Ecological systems are structured by feedacks, meaning that the dynamics of one component often affects others.
- Understanding ecological systems requires us to confront uncertainty, which can arise for various reasons.
- The dynamics and wellbeing of ecological systems are tightly intertwined with the wellbeing of human societies.
Photo by Matej Spulak on Unsplash
Over the semester, you will develop skills to:
- Describe how the field of ecology tackles complexity
- Explain how mathematical thinking helps generate
ecological insights - Interpret figures and results from published ecological literature
- Discuss the role of ecology in addressing major societal challenges.
Photo by Matej Spulak on Unsplash
Over the semester, you will develop skills to:
- Describe how the field of ecology tackles complexity
- Explain how mathematical thinking helps generate ecological insights
- Interpret figures and results from published ecological literature
- Discuss the role of ecology in addressing major societal challenges.
How many bats live in this group?
- Mark-Recapture as a method to estimate of population size:
- Capture and mark (tag) some number of individuals
- Release tagged individuals and allow the population to re-equilibrate
- Once population is settled (e.g. in the case of bats - on a different night), capture some number of individuals
- The proportion of individuals that are marked in your second sample can give you a good estimate of the total population size
How many bats live in this group?
Mark-Recapture as a method to estimate of population size:
\(N_{Marked}\): number of individuals marked in first sample
\(N_{Captured}\): number of individuals captured in second sample
\(N_{Captured,\ Marked}\): number of individuals in the second sample that are marked
\(N_{Total,\ Estimated}\): estimate of total population size
\[N_{Total,\ Estimated} = \frac{N_{Marked}*N_{Captured}}{N_{Captured,\ Marked}}\]
Worked example
On your first sampling day, you mark 200 bats with a metallic tag (\(N_{Marked} = 200\))
You return to the bridge next week, and capture 1500 bats (\(N_{Captured} = 1500\))
Of the 1500, only 17 bear the metallic tag mark (\(N_{Captured,\ Marked} = 17\))
Intuition: Since you marked 200 bats initially and only recaptured 17 in a large sample of 1500, you were only able to mark a small fraction of the bats!
\[N_{Total,\ Estimated} = \frac{N_{Marked}*N_{Captured}}{N_{Captured,\ Marked}} = \frac{200*1500}{17} \approx 17647 \mathrm{\ bats}\]
Course structure
What are we here to learn?
What is Ecology?
Ecology as a discipline is motivated by human efforts to
describe, understand, predict, and modify nature.Contemporary ecology research aims to understand
the factors that shape where organisms live,
how their abundances change over time,
how interactions shape communities and ecosystems,
and how these are affected by global environmental change.This course will introduce you to the questions that motivate the field of ecology, the approaches that ecologists take, and the implications of ecological research for societal challenges.
Photo by Matej Spulak on Unsplash
Common themes in ecology
- Ecological systems are dynamic, meaning that their properties can change over time.
- Ecological systems are structured by feedacks, meaning that the dynamics of one component often affects others.
- Understanding ecological systems requires us to confront uncertainty, which can arise for various reasons.
- The dynamics and wellbeing of ecological systems are tightly intertwined with the wellbeing of human societies.
Photo by Matej Spulak on Unsplash
Over the semester, you will develop skills to:
- Describe how the field of ecology tackles complexity
- Explain how mathematical thinking helps generate
ecological insights - Interpret figures and results from published ecological literature
- Discuss the role of ecology in addressing major societal challenges.
Welcome to
Principles of Ecology
Course structure
What are the logistics of the course?
This course will be administered through Moodle and
https://ecology.gklab.org.
Course rhythm
- In-class sessions will be a mix of lecture, hands-on activities, and discusssions.
- You are responsible for engaging with the Readings and other Resources made available to you on Moodle before coming to class.
- Most submissions will be due on Sunday nights at 11.59pm via Moodle; in some weeks, you will be asked to bring in copies of your submission to class (hard copy or digital copy on laptop/tablet is fine)
Evaluation and grading
Grading philosophy
- As an instructor, my goal for this class is for each of you to achieve the core learning objectives for our course.
- A huge body of research by colleagues in education shows that grades are a poor motivator for learning, and a poor predictor of future success.
- This shapes how the course is structured:
- No high-stakes, “one size fits all” exams
- Low-stakes assignments throughout the semester
- Considerable opportunity for each student to earn the grade they aspire to
Evaluation and grading
Your grade in this class will reflect your performance in three areas:
- Self reflections (biweekly)
- Biweekly activities
mostly completed outside of class, some in-class
- Semester project
more on this next week
Self reflections
- The goal is to help you take a step back and reflect more generally on your growth as a scientist over the semester
- I encourage you to think about how the material we are learning in-class relates (or doesn’t relate) to your life more generally
- I will include a list of potential reflection topics, but I encourage you to think broadly about what matters to you.
- First self reflection due next Sunday night (Sept 8), and then every other Sunday night.
Why self reflections?
- Learning happens not only through doing, but by reflecting on what we are doing (metacognition)
Why self reflections?
Make space for deliberately thinking about how lessons from basic ecology apply to our increasingly complex and “weird” environment
Reflect on what topics you find especially engaging and/or especially challenging
Evaluations of self reflections
- You are in charge of re-reading and evaluating your own self-reflections
- On every “off” week, you will be asked to return the previous week’s self reflection, reread your submission, and assign yourself a grade out of 10 points.
- Also explain why you are giving yourself this grade (2-3 sentences).
Evaluations of self reflections
Schematic for grading self-reflections
10 points: Deeply engaged with one or more of the reflection prompts (or other topics of your own choosing). Deep engagement could mean that you connected ideas from class to activities or observations outside, identified ideas or skills that you were finding difficult and contemplated potential ways of resolution, etc.
8 points: Engaged with the reflection prompts, but only in a cursory way. Did not go “beneath the surface” of any topic, rather just wrote down the first set of ideas that came to mind about the topic at hand.
6 points: Completed a submission that roughly counts as a progress update, but made no attempt to reflect on your learning, either in this course or outside of this course.
4 points: Made half an attempt at completing a submission.
0 points: Did not submit.
Self reflections
Themes for first self reflection:
Reflections on ecology
- What does the word “ecology” mean to you? How do you think it is relevant to your life?
- What is your relationship with “nature”? In your mind, how can humans have a healthy relationship with nature?
- Is there a particular place that comes to your mind when you think of “being out in nature”? What kinds of characteristics define that space for you?
Reflections on the semester
- What are some things you are excited about for this semester? What are some things you are nervous about?
- Looking at your semester schedule, are there going to be particular weeks that are looking busier (multiple exams/assignments due, etc.)? If so, how are you planning to prepare for these weeks?
- Two weeks into the semester, how do you see this course relating to the other courses you are taking, or to other activities in your life outside of this class?
Evaluation of self reflections
- Over the semester, you will have the opportunity to submit seven self reflections, each worth 10 points
- Only six of these will be counted towards the final grade, meaning that you have one “free pass”.
- Each self reflection comes with a 24-hour grace period for submission.
- I will read self-reflections to get a sense of how the class is going.
Biweekly activities
- Every other week starting in Week 3, you will be asked to complete an activity related to the material covered in the past two weeks
- The exact format will vary across the semester (e.g. reading primary ecological literature in some weeks; completing quantitative worksheet in another, etc.)
- Due on Sunday nights (or in some cases on Monday in class, if I am requesting a physical submission)
Evaluation of biweekly activities
- Graded by Dr. Kandlikar, following an “exemplar” that will be made available on Moodle.
- You will have an opportunity to earn back any lost points by completing an alternative version of the activity1.
- There will be 7 biweekly activities assigned through the semester, each worth 10 points
- Only six of these will be counted towards the final grade, meaning that you have one “free pass”.
Weekly readings and other resources
- Each week, I will post resources on the course website and moodle, which I expect you to complete before coming to class
- These will include a range of formats, including textbook chapters, primary ecological literature, podcast episodes, and material from the news.
This week’s resource
Co-Working sessions
- Each week, I will be available for two co-working sessions
- Please indicate your time preferences on the Moodle poll.
- Available for discussions regarding course content, professional development, etc.
Course structure
How is the material organized?
Levels of ecological organization
- Organism
- Population
- Community
- Landscape
- Ecosystem
Levels of ecological organization
- Organism
- Population
- Community
- Landscape
- Ecosystem
Photo by Jeffrey Hamilton on Unsplash
Population ecology:
How do individuals of a given species (“conspecific individuals”) interact with one another?
Does the nature of interactions vary across environments?
How do these interactions affect population dynamics?
Under what conditions do populations grow, shrink, or stabilize?
Photo by Mason Field on Unsplash
Community ecology:
How do individuals of different species (“heterospecific individuals”) interact with one another?
Does the nature of interactions vary across environments?
Why are some species able to coexist with one another over long timescales, while other sets of species cannot persist with one another?
What regulates the dynamics of species interactions across trophic levels (e.g. predator–prey interactions)?
Photo by Courtney Kenady on Unsplash
Landscape ecology:
What are the patterns of diversity across ecological gradients?
What processes give rise to variation in biodiversity across space and time?
How does human land use change restructure ecological communities?
Photo by NASA on NASA Earth Observatory
Ecosystems ecology:
How do energy and nutrients flow across ecosystems, for example at the scale of entire continents?
What are the consequences of disruptions to ecosystems cycles?
How do feedback loops shape the dynamics of ecosystems?
Photo by Matej Spulak on Unsplash
Common themes at all scales
- Ecological systems are dynamic, meaning that their properties can change over time.
- Ecological systems are structured by feedacks, meaning that the dynamics of one component often affects others.
- Understanding ecological systems requires us to confront uncertainty, which can arise for various reasons.
- The dynamics and wellbeing of ecological systems are tightly intertwined with the wellbeing of human societies.
Population ecology
What defines a population?
Individuals of the same species living together
Individuals interact with one-another
e.g. mating, facilitating, competing
How does a population grow or shrink?
- Birth (+)
- Death (-)
- Immigration (individuals coming in, +)
- Emigration (individuals leaving, -)
If we know a few of these rates, how can we predict population size time in the future?
How does a population grow or shrink?
Consider a ‘closed’ population
no movement in or out of a population:
immigration = emigration = 0Change in population size (\(N\)) only driven by births and deaths
There is some per-capita birth rate (\(b\)), and some per-capita death rate (\(d\))
Total number of births = \(b*N\)
Total number of deaths = \(d*N\)
How does a population grow or shrink?
- Change in population size over time is determined by total births (\(bN\)) minus total deaths (\(dN\))
\[\frac{dN}{dt} = bN - dN\]
\[\frac{dN}{dt} = (b - d) N\]
How does a population grow or shrink?
\[\frac{dN}{dt} = (b - d) N\]
- Define \(b-d\) into one integrative term \(r\)
\[\frac{dN}{dt} = r N\]
Populations grow when there are more births than deaths (\((b-d) > 0\); aka \(r > 0\))
Populations shrink when there are more deaths than births (\((b-d) > 0\); aka \(r < 0\))
The magnitude of \(r\) determines the rate of growth
How can such a simple population model help?
Implications of exponential growth
Ibn Khallikan’s story of the first chessboard
Estimating population sizes
Welcome to
Principles of Ecology
Estimating population size
What are some reasons that an ecologist would want to know the size of a population?
Tim Peltier, a biologist for the Alaska Department of Fish and Game in Palmer, explains one of the reasons why biologists have such an important job. “We count moose, caribou, sheep, and to a lesser extent bears and wolves,” he said. “The Board (of Game) has determined the population and harvest objective in each area and we are tasked with determining how close we are to those objectives. We need to have an idea of the population size.”
- Alaska Dept. of Fish and Game
Estimating population size
What are some reasons that an ecologist would want to know the size of a population?
Most often monitoring programs are designed to help managers and policy makers make more informed decisions. Monitoring allows decisions to be based less on beliefs and more on facts. We may believe that grasshopper sparrows in New England are decreasing in abundance because grasslands are being converted to housing (Figure 1.1). Only after a rigorous, unbiased monitoring program has been in place can we say that yes, indeed, the population seems to be declining (Figure 1.2) and that the decline is associated with the loss of grasslands.
- Monitoring animal populations: A practitioner’s guide
If you wish to harvest a lake trout population, one helpful bit of information is the size of the population you wish to harvest. If you are trying to decide whether to spray a pesticide for aphids on a crop, you may wish to know how many aphids are living on your crop plants. If you wish to measure the impact of lion predation on a zebra population, you will need to know the size of both the lion and the zebra populations
- Estimating abundance in animal and plant populations
Refresher on Mark-Recapture as a method to estimate of population size:
- Capture and mark (tag) some number of individuals
- Release tagged individuals and allow the population to re-equilibrate
- Once population is settled (e.g. in the case of bats - on a different night), capture some number of individuals
- The proportion of individuals that are marked in your second sample can give you a good estimate of the total population size
Refresher on Mark-Recapture as a method to estimate of population size:
\(N_{Marked}\): number of individuals marked in first sample
\(N_{Captured}\): number of individuals captured in second sample
\(N_{Captured,\ Marked}\): number of individuals in the second sample that are marked
\(N_{Total,\ Estimated}\): estimate of total population size
\[N_{Total,\ Estimated} = \frac{N_{Marked}*N_{Captured}}{N_{Captured,\ Marked}}\]
Activity for today
Form groups of 2-3 people each
Each group gets a bag with an unknown number of beans. This is your “true population”
Each bag indicates how many beans you should “Mark” in your first round of sampling.
Each bag also indcates how many beans you should “Recapture”
Mark the assigned number of beans once, recapture the assigned number five times.
Record \(N_{Captured,\ Marked}\) each time you recapture. Estimate your population size using the formula \[N_{Total,\ Estimated} = \frac{N_{Marked}*N_{Captured}}{N_{Captured,\ Marked}}\]
Once you are done with 5 “recaptures”, report your results to Gaurav.