Genetics & Evolution Box

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Link to lessons that are part of the Genetics & Evolution Box.

Project - Dragon Genetics

In this long term computer based simulation, students play with a fabulous FREE software program called Biologica developed by the Concord Consortium. It offers an in depth, virtual experience exploring ...

Snail Variations - Sources and Standards

Sources
This lesson was adapted from a lesson by Karen Kalamuck of the Exploratorium Teachers Institute.

For information on snails and snail care, see this website from the Lawrence Hall of Science.

The escargot recipe is taken from Gourmet Magazine, March 2001. A copy of this can be found at Epicurious.com.

Snail Variations - Going Further

Assessment

  1. Students’ data and graphs can be collected and graded.
  2. Written protocols for trait measurements can be passed between groups so that students get practice and feedback on writing a scientific protocol. You may wish to do this before having each group graphically represent their data. This extension generates considerable discussion on the causes of experimental error and measurement inconsistencies. It also allows the full characterization of the population of snails on a wide range of traits.

Snail Variations - Lesson Plan

Lesson Plan

  1. Discuss any ground rules (like do not hurt any snails) then jump right in! Pass out the snails, hand lenses, rulers, and stop watches. Ask groups to spend a few minutes observing the features and behavior of the snails.
  2. When students have had enough time to study the snails, have them close the lids. Ask students what they noticed. In particular, focus on how individual snails differ from one another. Discuss both the physical and behavioral traits of the snails.
  3. Ask students how these different physical and behavioral characteristics could be measured. Discuss the difference between subjective (bigger, faster, smarter) and objective (4.5 cm, travels 8 cm/min, figures out a maze in 2 min) measurements.
  4. Challenge students to pick a snail trait to measure. They should write down a procedure for their test and record the result for each snail that they were given. Everyone in the group must agree on the procedure such that the results would be the same, no matter who conducted the test. That means that your procedure should describe exactly what to do as if you were describing how to conduct the test over the phone to a friend. For instance, if you want to measure “size”, do you measure weight or length or width or height? If you measure length, what do you do when the snail is hiding inside its shell? Do you count antennae or not? Do you use centimeters or inches?
  5. Give students time to choose a trait, agree on a procedure and record their data. Circulate among the groups to help students that are struggling. Groups that finish early should be challenged to design a second procedure – possibly with the requirement that if they already tested a physical trait, that their second test should be of a behavioral trait.
  6. When all groups have finished, have them close the lids again. Discuss different ways to graphically present the results – pie charts, histograms, line graphs, etc. Tell students that they will be given 5 minutes to prepare a presentation for the rest of the class. Their presentation should include:
    • a description of their procedure
    • a table of results for their population of snails
    • a graphical presentation of their results

Snail Variations - Background

Teacher Background
Natural selection and evolution are core ideas in biology and, in fact, all of science. Natural selection can briefly be described the process by which those individuals whose traits best fit their environment are most likely to survive, reproduce, and pass their genes on to the next generation. One of the critical “raw ingredients” of natural selection is variation in a population. All natural populations (groups of organisms of the same species) vary in their traits based on the interplay between genetics and environmental factors.

This activity uses the common garden snail (Helix aspersa) to measure variations in a population. These animals are garden pests found throughout North America and are readily captured from around most neighborhoods in California. I generally pay my neighbor’s kids 5¢ a snail and end up with upwards of 40 snails in less than an hour.

Snails are incredibly easy to keep in the classroom. They can survive in the classroom almost indefinitely with regular feeding and cleaning. Keep snails in a plastic shoebox or glass terrarium. Keep the terrarium covered securely while letting in air for them to breathe. Snails are strong and can easily push off a plastic lid, so secure the lid with rubber bands if necessary. Stock their habitat with several wet paper towels and vegetables from the grocery store (lettuce, carrots, apples, etc.). Twice a week, clean out their habitat by throwing away the old paper towels and food and giving them new wet paper towels and food. If you are keeping the snails longer than a week, place pieces of chalk in each container since they need calcium for shell growth and repair.

At the end of your project, snails may be released if they were collected locally. It is often interesting to “tag” the snails before you release them with a dot of nail polish on their shells. Thus, individuals may be tracked over time. If you choose not to release these pests back into your neighbors’ gardens, they may be frozen then thrown away. The adventurous can try cooking and eating them. That’s right! The garden snails found in North America are the same species that is used in escargot. In the going further section, there are resources for how to make escargot – although beware… this may be traumatic to some of your students.

Student Prerequisites
None required although familiarity with observation, measurement, and histograms is helpful (see Human Traits Survey lesson).

Snail Variations - Logistics

Time
50 minutes to measure, quantify, and discuss variation in snail traits. The extension projects described in the Going Further section may last several months.

Grouping
Teams of 3-4 students.

Materials
For each group of 3-4 students you need:

  • 1 plastic shoebox
  • wet paper towels
  • vegetables
  • 4-6 snails
  • 2 hand lenses
  • 1-2 clear rulers
  • 1 stop watch
  • Optional: 2 bottles of nail polish in different colors

Other supplies you may want on hand for groups to share:

Project - Snail Variations

Variation in a population is the raw material on which natural selection works. How do scientists measure and quantify variation in traits? We use garden snails as a model organism ...

7. DNA Fingerprinting - Sources

Sources
If you are interested in creating a full-fledged CSI experience, an indispensable resource for teachers is the book, Mystery Festival, published by the Lawrence Hall of Science.

Other forensics science resources include:

  • Brian Bollone of Northpoint High School has made many of his teaching resources for his criminalistics and forensic science class available on the web.
  • Court TV has a wonderful series of mysteries to use in the classroom using a huge array of different techniques: DNA analysis, gunshot residue, pH testing, shoeprints, flame tests and more to solve the crimes.
  • DiscoverySchool.com has a large collection of forensic science resources for teachers.
  • Susan Seagraves created a fabulous “Whodunnit?” website with lesson plans for finger print analysis, chromatography, and mor.
  • The Shoder Education Foundation provides a comprehensive forensics resource for teachers including lesson plans, several mysteries, and resources.

7. DNA Fingerprinting - Assessment

Assessment

  1. Watch an episode of CSI that includes DNA fingerprinting data collection and evidence. Have students compare the techniques as seen on the show to the modeled version used in the classroom.

Going Further

  1. Have student run a gel in a virtual lab. The Genetic Science Learning Center at the University of Utah has a great online activity that allows you to load and run a gel
  2. If you have the equipment, teach your students to load and run a gel using any extracted DNA sample (see DNA Extraction lesson). Even if you don’t have gel boxes and fancy equipment, you can create your own functional gel boxes out of grocery store materials. The best write up for DNA extraction and running a gel “MacGyver style” can be found at BioTeach.

7. DNA Fingerprinting - Lesson Plan

Lesson Plan
Day 1+ - Investigating the crime scene
If you set up a crime scene, make lots of observations of the crime scene. Start with all the kids outside the crime scene area, drawing pictures and writing down the things they notice. Finally, allow one student at a time enter the crime scene area wearing gloves to collect evidence. Evidence should be kept in plastic bags. Analyze any non-DNA evidence first. Dust for fingerprints. Collect hair and fiber samples. Perform paper chromatography on the ransom note and compare it against the pens in the possession of the various suspects. (See Sources section below for resources and lesson plans describing how to conduct these tests.)