Biol 208 Lab 3: Mark & Recapture PDF

# Lab 3a: Effects of stress on plant growth and reproduction (Set-up) ## Overview - This is a two-part lab. - You will work in bench groups to set up and harvest the experiment, but the assignment is done individually. - **Part 1 (Set-up):** Design and set up a manipulative experiment to determine...

# Lab 3a: Effects of stress on plant growth and reproduction (Set-up) ## Overview - This is a two-part lab. - You will work in bench groups to set up and harvest the experiment, but the assignment is done individually. - **Part 1 (Set-up):** Design and set up a manipulative experiment to determine the effect of stress on plants. - **Part 2 (Harvest):** After 4 weeks, harvest plants and collect data. Perform an ANOVA statistical test. - You will write a full scientific lab report on this experiment. - It is an individual assignment. ## Objectives At the conclusion of this lab, participants will be able to: - Design a manipulative experiment to study the ecology of an individual organism - Evaluate the range of tolerance, optimal performance, and phenotypic plasticity of an organism - Analyze and interpret data using ANOVA and Tukey HSD statistical tests - Apply Tukey HSD test results to a graph using letter significance groupings - Compose a formal scientific lab report to communicate your results ## Connections to the lecture material: - How do organisms deal with resource constraints? - What is the law of tolerance? - What is acclimation and how does it relate to phenotypic plasticity? - What are trade-offs and why do they occur? ## Introduction: Designing a manipulative experiment - In some types of experiments, a hypothesis is tested by measuring different variables and looking for patterns in the data. This type of study is called an observational experiment. - However, sometimes a hypothesis can be more effectively evaluated by intentionally manipulating a factor that you hypothesize is driving the observations you have made, while controlling as many other competing factors as possible. This is called a manipulative experiment. - Designing a manipulative experiment, even a simple one, requires considering some or all of the following: ### Questions to consider: - What variables related to my observation can I examine? - How can I treat or manipulate those variables to get a response? - How can I measure the response? - What will I use as a control? - How does my manipulation relate to natural or predicted variation? - How will I analyze the data? - How does the experiment relate to broader questions or topics in my field? # 3-2 EFFECT OF STRESS ON PLANTS: SET-UP - In this lab you will work in groups to design a manipulative experiment to test how a stressor affects plant individual ecology. - Your group will conduct the experiment, measure appropriate response variables, and analyze your data. - You will then present your findings in an individual lab report. ## Tolerance, plasticity, trade-offs and optimal performance - The range of tolerance is the entire range of conditions in which a plant can survive. - Within the range of tolerance, plant performance can range from: ### Range of Tolerance Summary | Performance | Explanation | |---|---| | Optimal | Usually corresponds to a small subset of optimized conditions that maximize BOTH growth and reproduction | | Growth Only | Also called the "optimum" | | Growth, No Reproduction | Sub-optimal conditions | | Survival, No reproduction, No Growth | Due to decreased energy produced at suboptimal conditions, plants will be able to grow, but do not have enough energy to undergo reproduction | | Survival, No Growth| When most of the energy is going towards survival, the plant can't grow OR reproduce | - **In environments that fall within the optimum range, a plant can expend most of its energy on processes that enhance fitness, such as growth and reproduction, and allocate less to basic survival and maintenance.** - **When encountering physiologically stressful conditions outside of its optimum, however, a plant must allocate more energy towards basic survival.** - **Outside of the range of tolerance the plant is unable to survive.** - **Some plants can grow in a very wide range of environmental conditions.** - **To maintain essential processes in widely varying conditions, plants must employ specific strategies, including morphological or phenotypic adjustments, which allow them to extract resources as needed.** - For example, when growing in nutrient-limited environments, plants will allocate more resources towards root growth to access the resources they need. - Plants may also adjust their specific leaf area in order to access more or less light for photosynthesis. - **This flexibility in phenotype under different environmental conditions is known as phenotypic plasticity.** ## Brassica rapa - In this experiment, you will examine the effect of stress on **Brassica rapa**. - *B. rapa* is from the crucifer plant family, closely related to broccoli, cabbage, canola and Arabidopsis thaliana, a model organism for plant biology. ## During this lab, your group will select an abiotic factor that you consider to be ecologically meaningful. - You should be prepared to justify why you have selected this factor in the introduction of your lab report. - **The manipulation that you will be performing can be simple, but you still have the opportunity to ask a complex and meaningful ecological question.** ### Potential Research Questions - What effect does using salt to control ice on Edmonton roads have on plant growth in the spring？ - How does the topography of the soil influence plant growth? - How would soil acidification affect plant growth and reproduction? ## When designing your manipulative experiment you will want to test your abiotic factor at three different treatment strengths. - After you have implemented your treatments, you will grow your plants in the growth chamber until they are ready to be harvested. - After four weeks of growth, you will harvest your plants and measure two response variables—one related to growth and one related to reproduction—to determine whether the treatments incurred a cost to your plants and, if so, whether this cost increased as treatment levels increased. ### Questions to consider when designing your experiment and formulating your hypotheses: - Will your abiotic factor affect plant growth and plant reproduction in different ways? - Will variation in the intensity of the stress lead to differences between treatments? - Will there be costs or tradeoffs in your treated plants relative to your control plants? - What specific responses might you expect (and why) and how might you quantify them? ## Lab 3b: Collecting Ecological Data: Sampling by Mark and Recapture ### Overview - You will use bean beetles to perform a mark and recapture experiment for estimating population sizes. - You will compare this technique with the quadrat sampling you did last week. ### Objectives At the conclusion of this lab, participants will be able to: - Perform a mark-recapture experiment - Calculate population size estimates - Compare and contrast the assumptions and advantages of mark and recapture with quadrat sampling you have done in earlier labs ## Connections to the lecture material: - What is a population? - Why is sampling necessary? - How are population sizes estimated? ## Density estimation Two common methods of estimating absolute population density are: 1. **The quadrat method** - Used for small, sessile or relatively sedentary organisms (non-motile). - You did this last week in the map simulation AND in the River Valley. 2. **The mark/recapture method** - Used for relatively large and/or mobile organisms. - You will do this in lab this week using bean beetles ### Mark/Recapture - Mark/recapture is used to quantify population density of moving organisms. - The mark/recapture technique follows these steps: 1. **Capture (sample) a number of individuals** 2. **Mark them** 3. **Release the marked individuals back into the population and allow them to randomly disperse** 4. **Recapture a random sample of individuals, noting the number of marked and unmarked individuals in the sample** ### 3-10 MARK AND RECAPTURE - There are several important assumptions in the mark and recapture model: 1. Marks must not be lost or overlooked. 2. No change occurs in the ratio of marked to unmarked animals in the population as a result of birth, death, immigration, or emigration. 3. Marked and unmarked animals are similar in all aspects (e.g., mortality rates, activity, trappability). 4. The probability of recapture is equal for marked and unmarked individuals. - Each of these assumptions may be violated in studies of natural populations. Field ecologists must be aware of these assumptions and assess how well or how poorly they are met in a particular study. - Using simple proportions, we can estimate the total population size from a mark/recapture experiment: $$ N = \frac{M \times n} {m} $$ - Where: - **M = total number marked in the population** - **N = total population size** - **m = number marked in the sample** - **n = total number in the sample** - Rearranging this equation, the estimated total population size (called Ñ to symbolize that it is an estimate) is: $$ \hat{N} = \frac{M \times n} {m} $$ - **N must be a whole number.**** We will always round decimals to the next whole number, regardless of mathematical rounding conventions (e.g. 15.2 is rounded up to 16).** - If you look back to the quadrat sampling (map) activity last week, you will see the mathematic calculation for estimating total population sizes using quadrats and mark/recapture are very similar. Both methods work on a similar principle of creating a mathematic proportion of the sample to extrapolate up to the entire population. - **Try this one:** - You have used a mark and recapture experiment to determine exactly how many white-tailed jack rabbits are living on the U of A campus. - First, you captured and marked 10 rabbits. - You released them back onto campus and resampled one week later. - During resampling you captured 10 rabbits and 2 were marked. - What is the estimated population size (remember to raise to the next whole number)? - Use this space to work though this example. - **Estimated Population Size: ** *** This document contains information about lab 3a and 3b. It describes the steps of conducting an experiment by introducing a stressor to a specific plant, *Brassica rapa*. It also describes the methods of calculating the population size using quadrat method and mark/recapture method.