Ecology & Evolution

Bouquet of Flowers

PDF File, 108K

This series of four different lab activities all relate to flower reproduction.  They have been designed to relate to each other and to stand alone.

Name that Pollinator focuses on adaptations for successful pollination.  Both pollen and pollen vectors are examined.  Observing, data gathering, making measurements through the microscope, and constructing tables are all emphasized.  This lab would work equally well in ecology, evolution, or reproduction units.

The World’s Best Artificial Flower is a cooperative learning venture which has students either construct 3-D models or write essays on a fictitious flower, pollinator, habitat system.

In Flower Dissection, students identify, remove, arrange, and tape down the essential and accessory parts of a flower.  Students also examine pollen grains and the possibility of pollen tube formation.

"To form a pollen tube...or not to form a pollen tube," allows students to design their own experiment to investigate some variable influencing pollen germination.  The parts of a research paper are outlined and students are expected to follow that format when writing their final report.

Comparing Aquatic Communities

PDF File, 100K

Teams of students measure physical and chemical characteristics of different sites in streams and/or ponds and collect benthic invertebrate organisms.  They interpret patterns in the structure of the biological community at each site in light of the abiotic (physical and chemical) and biotic nature of the environment.

Food Preferences of Slugs

PDF File, 104K

Students will investigate the food preferences of garden slugs (Arion subfuscus) using simple equipment including margarine tubs, graph paper, scissors, and common plants, both wild and cultivated.  The exercise is genuine scientific research in that:  a) the student devises his/her own "research question" about slug feeding behavior, and b) the results are truly unknown to the student-experimenter (and possibly to the instructor) prior to the experiment.  In carrying out the complete set of experiments described below, students learn that one way to achieve precision and accuracy is by designing experiments with many replicates.

The following laboratory write-ups are included:

1. Slugs and the Scientific Method: This exercise uses slugs to teach the difference between "observation" and "opinion" and introduces the concepts of "controls" and "hypothesis testing."
2. The Vermiculturist’s Experiment: This paper exercise illustrates the importance of controls, variables, and replicates in experimental design.
3. Food Preferences of Slugs: Students design and carry out their own experiment to test a slug’s preference between two or more food sources.
4. Food Preferences of Slugs (continued): Students will also benefit from the opportunity to further practice their experimental design skills by looking more closely at the complex question of "How do you determine what a slug really likes?"

Goldenrod Gall Size as a Result of Natural Selection

PDF File, 252K

This investigation examines natural selection and coevolution using goldenrod (Solidago canadensis), its stem gall insect (Eurosta solidaginis), and associated parasites, parasitoids, and predators that feed upon the stem gall insect (i.e., Eurytoma obtusiventris, Eurytoma gigantea, Mordellistena unicolor, and birds).  Through measurements of gall size and an investigation of events occurring within the galls, a correlation between gall size, frequency of predation, and type of predator can be made.  An analysis of histograms and data tables charted from gall measurements and frequencies of various events leads to the conclusion that parasitic organisms select goldenrod galls within specific ranges of size.  A statistical analysis using standard deviation and tests of reliability also lead to the conclusion that the forces of natural selection and coevolution are operating within this stem system.

Photosynthesis and Respiration in Elodea

PDF File, 60K

This lab involves the qualitative measurement of the changes in carbon dioxide concentration associated with both respiration and photosynthesis in the fresh water plant Elodea.  Bromthymol blue is used as an indicator for the presence of CO₂ in solution.  When CO₂ dissolves in water, carbonic acid is formed.  A bromthymol blue solution, acidified to pH 6.0 by the addition of carbon dioxide produces a yellow color.  The blue color is restored when the CO₂ is removed and the pH becomes higher than 7.6.

Students are responsible for the basic design of this investigation.  Given a list of tasks, and the student background sheet entitled "Photosynthesis and Respiration in Elodea," they are asked to design an experiment which will allow them to demonstrate the use of CO₂ by a green plant in photosynthesis, and net production of CO₂ (by respiration) in the absence of photosynthetic activity.

The Plant Game

PDF File, 112K

This exercise presents an opportunity for students to think about —- in a fun and enticing manner —- how plants grow.  In the Plant Game, teams of students "grow a plant" composed of "leaves," "roots," and "flowers."  The goal of the game is to produce a maximum number of flowers.  This is possible only if the students have a good strategy to keep their "roots" in water and produce enough "leaves" to support adequate photosynthesis.  Students "grow their plant" in a graduated cylinder in which the paper clip roots dangle in water.  Measured amounts of water are added to and removed from the system by "rainfall" and "transpiration," respectively, which are determined according to a roll of the dice.  The game ends when another roll of the dice indicates a "frost."  Since the rate of growth of each student’s plant is limited by the "weather" and by the students’ choices in how they allocate their fixed carbon, a few repetitions of the game clearly demonstrate the functions of leaves, roots, and flowers, and some of the environmental stresses on plants.

The data collected during this game lends itself well to graphical analysis.  Students may graph various parameters of their plants’ growth and compare the results from one "season" to the next or between strategies for growth in a single season.