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3.3 From Data to Death

Teacher Background

It's pretty obvious that Antarctica's unique climate and environment drive the processes which shape the life and death of the creatures who live here. But what's been happening in the past few years is an increasing understanding of exactly what aspects of the environment seem to have most impact on the food chain and which species thrive or struggle. The data which reveal these patterns aren't seen in majestic icebergs, or images of cute penguins, but in vast strings of numbers detailing myriad, individually inconsequential details about the size and distribution of creatures, temperatures, ice area, and other factors, collected over many years and then "crunched" into meaning.

Charles Darwin once wrote that the secret forces of evolution were "time and death." This Activity, bluntly called "From Data to Death", introduces students to two simplified data sets, supplied by researchers Robin Ross and Bill Fraser, and invites students to investigate the patterns hidden in them. With luck, the original researchers themselves will be looking over students' shoulders with hints and tips!

Sidebar: David M. Karl

Here's some background on Robin Ross' krill data (you can find more in the Blackline Masters for this Activity, and on-line): Antarctic krill release many eggs in the ocean, but just like fish, many krill die before they reach adulthood. There's a lot of year-to-year variability in mortality rates, however, and one of the important aspects of the LTER research project is trying to understand exactly what aspects of the environment affect survival of these young krill. "Length frequency distribution", or how often a particular size occurs in the sample of krill collected, is one of the analyses routinely done on the Polar Duke. When measuring a krill, the LTER scientists use the following standard: total length is from the tip of the "rostrum" (the pointy bit between the eyes) and the tip of the "uropods" (near the end of the tail) and is measured in millimeters to two decimal places. Thus, krill measuring between 8.5mm and 20mm were hatched during the previous austral (January to March) summer. The year-to-year length distribution data combined with other environmental data (sea ice variability, weather, Adelie penguin and skua population statistics) provide data sets for scientists to analyze in order to better understand the structure and function of the Antarctic marine ecosystem.

Objectives

To simulate sampling techniques, students will utilize random selection to collect middle school height data.

Students will analyze, organize and graph given sets of Antarctic data.

Students will go on-line to question the Antarctic researchers, and discuss possible explanations for given sets of Antarctic data.

Materials

  • transparency of krill (made from Blackline Master #16)
  • copy of Robin Ross' krill data (Blackline Master #17) and description of sampling procedures
  • copy of Bill Fraser's data (Blackline Master #18)
  • grid paper
  • rulers
  • markers
  • computer/spreadsheet application software (optional)
  • metric tape measures
  • data collection sheets (student made)

Engage

Ask students to estimate the average height of all the students in their middle school. Record all guesstimates on chart paper. Then ask students how they might obtain the data necessary to
measure the average more accurately and objectively. Discuss the difficulties of attempting to sample every student in the school.

Explain/Explore

Review with students the purposes of LTER research in the Antarctic and the specific data collection techniques used by the krill group (random sampling at specific locations around the Palmer Peninsula, use of bioacoustics, and measuring of krill body lengths). Explain that LTER scientists cannot measure every krill at each location! Instead they use a technique known as random sampling to collect a set of data that represents the total population-they measure the lengths of 100 krill at each location.

Tell students they will use this technique to gather data that represents the distribution of body heights in their school.

Procedure

  1. Working in small teams, students will measure the height of every tenth
    student entering the building on a given morning. Each team will be assigned a specific entrance to monitor. Advance planning should include the following:
    1. cover all entrances (which ones have highest morning traffic?)
    2. consideration of structural factors, e.g. do all the older (taller?) students arrive early some mornings for some specific activity?
    3. establish standard measurement techniques
    4. efficient recording of data
    5. permission of school administration
    6. advance notification/explanation of event to staff and students
    7. compilation of data
  2. After data collection has been completed, students may create simple bar graphs showing data distribution.
  3. Mean, median, mode should all be reviewed. Students compute average.

Data Analysis

Engage

Display transparency of krill (Blackline Master #16) on screen. Ask students to estimate the length of a krill in millimeters. Record all measurements on chalkboard; find range of measurements.

Explain/Explore

Procedure

  1. Distribute Robin Ross' krill data. Review and discuss headings for each column of data. Direct students to begin analyzing the raw data with the following questions:
    1. What factors might have influenced the data collection on a given cruise?
    2. Were the months all the same? the years?
    3. Which cruise collected the most data? the least?
    4. What is the smallest number? the largest?
  2. Review the life cycle of krill (See Krill to Kill? Blackline Master #10). Explain that krill with body lengths from 8.5mm to 20mm were born the previous austral summer. Direct students to examine the data to find the greatest incidence of these small body lengths. What might this indicate to scientists? (successful "recruitment")
  3. Ask students how this data might be organized so that it's more easily analyzed and understood. (numbers can be arranged from smallest to largest, data can be made into a graph)
  4. Pair students and randomly assign (pick out of a hat!) one data set for each pair. Have students work cooperatively to create a graph representing their data set accompanied by a written paragraph summarizing the data.
  5. Go on-line with questions to Robin Ross during program 1, or submit via Researcher Q&A.

Extend/Adapt/Connect

Distribute Bill Fraser's data set, which includes krill data along with sea ice extent, length of penguin foraging trips, and the number of breeding pairs. Assign students to small data analysis teams with the following tasks:

  • What categories of data were collected?
  • How many samples were collected?
  • What variables are being compared?
  • Based on this data, what inferences might be made?

computer logo

Go on-line with questions to Bill Fraser during Program 2, or submit via Researcher Q&A.

Students may enter the data sets into spreadsheet or graphics programs, and create a computer-generated graph or display.

Go on-line via discuss-lfa, to share ideas with other teachers using this Activity.

globe logo

Research and illustrate the life cycle of krill.





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Last Update: 1/18/97
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