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BI 101 Online Lab Procedures
Lab 2: Survivorship, Distribution, and Population Growth
Learning Objectives:
By the end of this lab you will be able to: ● Create a survivorship curve. ● Describe how parental care affects offspring survivorship. ● Determine the index of dispersion for a population. ● Use population growth equations to predict the size of a population.
Additional resources needed:
The following resources are located in the Week 2 “Research and Report” section of the Moodle course. ● Lab 2 Report: You will record your data and answer analysis questions in this report. Once
complete, you will submit this report through the submission page on the course website. ● Lab 2 Spreadsheet: This document has tables and graphs that you will generate as you go
through the activities outlined in this document. It is not to be turned in, but you will need it to create graphs and analyze your data.
It is highly recommended that you print this document to facilitate ease of access while
completing the activities.
Before you begin this lab, obtain the following items from your lab kit:
● Feathers
You will need to provide:
● 25 local obituaries from 2018
Introduction to Survivorship
Within a population, some individuals die very young while others live into old age. Until quite recently, the pattern of mortality for humans has been influenced primarily by disease. When the number of survivors of a population is plotted against time or life span the graph is termed a survivorship curve. Three patterns of survivorship are recognized. These three can be displayed by survivorship curves, graphs that indicate the pattern of mortality in a population. While survivorship curves for humans are relatively easy to generate, information about other species is more difficult to determine. It can be quite a trick to simply determine the age of an individual plant or animal, not to mention watching an entire population over a period of years. However, the principle of determining survivorship can be demonstrated by using population data and non-living objects. In this exercise you will produce survivorship curves using data from obituaries and feathers.
Part 1: Human Survivorship
Obtain obituaries from your local newspaper or website source. You will need 25 for this exercise. 1. Complete Table 1 found in your Lab Report by recording the year born, the year died, and age at
death for 5 individuals found in your obituaries. Place a “1” in each cell if the individual lived to that
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age interval (AI). For example, if the age at death was 43, then the first 5 age interval columns would be marked with 1’s. If the individual did not survive into a particular interval, enter a “0” in the corresponding box. When all rows are complete, add together all of the numbers for each column and record the total in the last row of the table. These totals represent the number of individuals that survived into that interval. You should have a total of 5 for the first AI. As your population gets older, you should see this number decrease.
2. Using the lab spreadsheet, create a survivorship curve for your sample size of 5 in the spreadsheet. Open the lab spreadsheet. Click on the first tab at the bottom of the spreadsheet titled “Human Survivorship 5”. Enter your totals from the last row Table 1 into the yellow highlighted column in the spreadsheet. A graph will be automatically generated. Add an image of your graph into your lab report. The easiest way (that I know of) for PC users to do this is use the Snipping Tool . Mac users can take a screenshot of part of your screen . Save as an image and insert it into your lab report.
3. Now use the spreadsheet to create another survivorship curve, but this time using a sample size of 25. Click on the second tab titled “Human Survivorship 25”. Notice that the type of data being plotted has changed. When reporting data in populations that are large, it is easier to analyze the data as a percent of the population instead of actual headcounts, as you did in the first graph. In the yellow highlighted column, enter the year born for 25 individuals you found in your collected obituaries. (It’s ok to use the 5 you already used in your first data set).
4. Answer the questions in the lab report, using the two graphs you just generated.
5. Click on the tab in the spreadsheet titled “Human Survivorship Historical”, observe the survivorship curves of human populations during different points in history, and discuss your observations in your lab report. Please note, the green line that represents deaths after 1940 is created from your data set of 25 individuals, so you must complete that graph to answer the question in the lab report.
6. Using your graph with 25 data points, interpret the data by answering the questions in the lab report. Make note of the differences in how the data is reported when answering the questions! Remember, your population of 5 is reported as total number of people still alive, while the population of 25 is reported as percent of the population that is still alive.
Part 2: Feather Survivorship
You learned that the three different types of survivorship curves indicate certain characteristics of that species, including level of parental care. In this activity, you will test this using feathers as your test “species”. You will measure the “time to death” after tossing each feather into the air. “Time to death” is recorded as time that passes from the moment the feather leaves your hand to the moment the feather touches the ground or other surface. You might find it helpful to enlist the help of a volunteer to assist you in monitoring time until death. Population 1 – Control Set: Do not give any assistance to the feather to keep it “alive”, just let it be. Record the time it takes to land.
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Population 2 – Parental Care: Once the feather leaves your hand, you will give your “offspring” assistance to keep alive. You can wave a paper or your hands under it, blow it upward to keep it going, or fan it somehow in an effort to keep the feather in the air and prevent it from hitting the ground (“dying”).
Instructions:
1. Toss a feather in the air or drop it from an elevated height. Time starts when it leaves your hand. 2. Observe and time how long the feather takes to land (in seconds). Assume the maximum lifespan is
30 seconds. If it takes longer than 30 seconds for the feather to drop, enter 30 into your chart. 3. Record your data in Table 2 of your lab report. Repeat steps until you have 20 data points. 4. Transfer your data to the Feather Survivorship tab in the Spreadsheet. 5. Save your graph, similar to how you saved the survivorship curves, and insert it into the report. 6. Answer the analysis questions in your lab report.
Part 3: Distribution Patterns
Ecologists use the term “dispersion” to describe the distribution pattern of individuals in their habitat. This pattern may vary from a random, uniform, or clumped distribution. Dispersion can be an important factor in evaluating the impact a population can have on its habitat or how exploiting a habitat can impact a native population. For example, the action of an equal number of clumped individuals will be different than if the same number had been uniformly distributed.
Instructions:
The last page of this lab represents a 100 square meter (m2) intertidal area that is the habitat for a variety of marine plants and animals, among them algae and sea urchins. Print out the last page and use it to determine the pattern of dispersion by following the instructions below: 1. Using a penny, flip the coin onto the page. Where the coin lands, count the total number of algae that
are touching any part of the coin. Record this number in Table 3 in your lab report. Repeat this process 20 times.
2. Use Table 4 to summarize your data. a. Column 1: Target Species per Plot (X)
This column represents the number of individuals that were touching the coin with each flip.
b. Column 2: Number of Plots (E) Look at your data in Table 3. How many times did you flip the coin and not land on any algae? This is the number that is recorded in the first row. How many times did your coin land on 1 algae? Record this number in row 2. For example, if your coin touched 3 algae four coins flips out of 20, then you enter “4” into the row where X=3. Repeat this until all pertinent rows are complete.
c. Column 3: Number of Algae Counted This column represents the total number of individuals that were touched with each flip (Column 1 multiplied by column 2). For example: If (X) = 3, and (E) = 6, then 6 of your 20 coin flips resulted in touching 3 algae, and you counted 18 individuals. (6 flips x 3 algae = 18 algae counted).
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d. Totals The last row of the table is the sum of each column of data. (n) = Total number of coin flips (N) = Total number of algae counted
3. In the spreadsheet, click on the “Index of Dispersion” tab. Enter your data from column 2 of Table 4
into the cells highlighted in yellow. Make sure your own calculations correspond with those generated in the spreadsheet. You should see an index (Id) value automatically in cell C24, calculated after you enter your (E) values. Record this index in the last row of Table 4.
Use the following information to determine the distribution pattern of the algae. You will discuss the value in part 4 of the lab report. (Note: Your calculated Id will probably not be exact, but should be much closer to one of the following values than the others.)
If Id = 1, then distribution pattern is random. If Id = n, then distribution pattern is clumped. If Id = 0, then distribution pattern is uniform.
Part 4: Population Growth
The last page of this lab (the same that you used in Part 3) represents a 100 square meter (m2) intertidal area that is the habitat for a variety of marine plants and animals, among them algae and sea urchins. The date at time of count is December 31st, 2015 (end of year)..
Instructions:
Using the printout on the last page, count the number of algae and sea urchins present in your tide pool on December 31st, 2015. Record these numbers in Table 5 of the lab report.
Density and Distribution of Algae
1. Calculate the density of the algae. Recall that species density refers to the amount of space an individual takes up in a habitat. Your answer should be expressed as # of algae per square meter (Units must be included!). Not sure how to calculate density? The lecture materials has examples!
2. Identify the index of dispersion you calculated in part 3 in your lab report.
3. Discuss what this index tells us about the lifestyle of algae
Sea Urchin Population
1. On January 1st, 2015, the sea urchin population consisted of the adult urchins and those that died throughout the year. (Remember, the young urchins were born after January 1st!) Determine the population size at the BEGINNING of 2015 and record in your lab report.
2. On December 31st, 2015, the urchin population consisted of all the adult sea urchins plus those that were born during the year. (Remember, the dead urchins can’t be counted as part of the population at the end of the year since they are dead!) Determine the population size at the END of 2015 and record in your lab report.
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3. Using the population size you determined for the beginning of the year, determine the birth rate (b) for the sea urchin population in 2015. Record this in your lab report.
4. Again using the population size you determined for the beginning of the year, determine the death rate (d) for the sea urchin population in 2015. Record this in your lab report.
5. Calculate the growth rate (r) for the sea urchin population.
6. Using your calculations, predict the growth of the sea urchin over the course of 5 years. Remember: G = (r) x (population size). G represents the number of individuals added to the population within a given time frame. Refer to the lecture slides and study guide to see examples of how to determine population size over the course of several years. Start your calculations using the original population size you calculated at the beginning of the year in 2015.
7. Record the population size for 5 years of growth in the last section of the lab report and discuss your results.
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