Discussion: Are seeds exposed to some leaf extracts slow to germinate? do they ever germinate, over the duration of the experiment? what must be going on? do you think it might go on in nature? what possible benefit could there be to a plant of inhibiting the germination of other seeds? might this have some role in agriculture? might weeds have detrimental effects on crop plants, other than usurping space, light, water, and fertilizer? what effect do you think this phenomenon (assuming this has worked) has on the distribution of natural plants? do you think that the strength of its action might vary with climate? etc. etc.
88. Ant Wars
Question: Do ants of different colonies hate one another, and is the intensity of hate dependent on the frequency with which they are likely to encounter one another?
Note: This activity sort of goes against the “no gratuitous destruction of animals” restriction that forms the core of our philosophy, so it should be developed with discretion.
Season: S, F.
Framework: 8a (4c).
Background Information: Note that ants have “colony odors;” not only do ants of different species have different chemistries, such that they “smell” very different to another ant, but even ants belonging to different colonies of the same species apparently have different chemical cues.
How To Do It: Find an ant mound (fire ants or Conomyrma). Pick up one of its inhabitants and drop it back into the middle. Note the response, or lack thereof. Now find an ant of another species and drop it into the middle. Note the response. Continue. Then find another fire ant or Conomyrma mound at least 10 m distant. Make reciprocal drops: an ant of A into B, an ant of B into A. Note the response. Continue, using fire ant mounds far from and close to one another; but always noting the distance.
Discussion: What is the pattern of aggression with distance? Do ants from very close mounds like each other? why might this be so? what about intermediate distances? what about far distances? how might you explain this? What effect does “ant hate” have on the spacing out of ant mounds? Judging by your results, are mounds of different species likely to be as spaced out as mounds of your test species? Why are ants so aggressive? What is being defended? etc etc.
89. Bird Feeder Bullies
Question: Who’s the boss of the bird feeder, why, and does being the boss mean you get all the seeds, or are there “alternative tactics” to getting fed?
Framework: II-8-A (I-3-C-ii).
Needed: An established bird feeder. Pencil and chart paper. Field guide to birds.
Notes: The similarity of this to #85 is not accidental. This activity can be done on the spur of the moment, or repeatedly, but it does require that the feeder have frequent avian visitors. It’s best done during a cold spell, when birds are especially attentive to feeders.
How To Do It: Simply put out a new stash of seed and wait for birds to accumulate. Meanwhile, make up a chart, with all known feeder species listed along the top and along the side. Label top “winner” and side “loser.” Each time there’s an aggressive encounter between two birds, of the same or different species, students will make a tally mark in the appropriate square.
So: note the first birds to come and discover the seed stash. Note what happens when the next species comes. Continue to accumulate data on interactions as long as the teacher wants. Notice what the “wimps” do—how do they get food? Does being bully ensure a good food supply? At the end, construct a dominance hierarchy among species.
Discussion: Is the dominance hierarchy transitive or intransitive (of course you don’t have to use this jargon!) - that is, does A beat up on B, B on C, C on D, and so forth, or does A beat up on B beat up on C beat up on A. Is the “top dog” also the biggest bird? the brightest colored? the loudest? the most likely to be in groups? What are correlates of position on the dominance hierarchy? What about the “bottom dogs”—what do they do to stay alive? Etc. etc.
Question: Can you predict which habitat will have the greatest diversity of active litter foragers?
Season: Spring, Fall (This must be done on a dry night—do not do this during very wet weather).
Framework: III-11 (III-10).
Needed: Empty quart yogurt or cottage cheese containers; a garden trowel.
How To Do It: Students decide on several habitats to sample, ranging from the middle of the trampled/ barren spots to the most complex, most natural habitat available on the ground (don’t hesitate to include flower beds, next to building wall, under planted shrubbery, etc.). Make sure that at least two replicate sites are sampled, of each habitat chosen (otherwise we’ll be teaching students to pseudoreplicate).
Each student or team gets to bury one plastic container. The container should be buried so that the rim is exactly even with the ground surface, and the ground surface around it should be returned to as close to the pre digging state as possible so that foragers will not veer off.
Students come up with consensus prediction of which habitats will have the greatest number of different kinds of foragers, which habitats the least, and must give reasoning for choices. Pitfall traps are left overnight. The next day look to see what’s there and try to figure out what it is and what it eats.
Discussion: Were the predictions upheld? What kinds of animals were captured? Why do you think there were these differences in diversity? What does “diversity” mean—does a more diverse group of animals have a different effect on the biological community than a less diverse group? Are all kinds of creatures caught equally abundant? Are some more common than others? Are ones more common in a given trap also more widespread, that is, do they occur in more different kinds of habitats? Are rare ones quite restricted in habitat choice? Do you have to “worry” about rare ones more than common ones? Etc. etc. You might need to leave pitfall traps over two or three nights.
Extension: If students really get into this, traps could be run once a week year around, for an activity related to framework reference I-2-D.
91. Things That Eat in the Night
Question: Can you predict which habitats will have the greatest diversities and numbers of scavengers and decomposers, and what are some of the ramifications?
Season: Fall, Spring.
Framework: III-11 (III-10, II-7-A, II-7-B).
Needed: Empty quart yogurt or cottage cheese containers; a garden trowel, and bait. Possible acceptable baits are smelly tunafish, rotten meat, rotten bananas, other rotting fruit; use your imagination. By far the best bait is human excrement, but I bet that wouldn’t go over too well with the PTA. In a rural area, though, it might be acceptable to use cow dung (which is about 1% as good as human . . . says something, doesn’t it, that humans generate better . . .; anyway...)
How To Do It: Procedure is as #90, above, but use baited rather than unbaited pitfall traps.
Students decide on several habitats to sample, ranging from the middle of the most trampled/ barren area to the most complex, most natural habitat available (don’t hesitate to include flower beds, next to a building wall, under planted shrubbery, etc.). Make sure that at least two replicate sites are sampled, of each habitat chosen (otherwise we’ll be teaching students to pseudoreplicate).
Each student or team gets to bury one plastic container. The container should be buried so that the rim is exactly even with the ground surface, and the ground surface around it should be returned to as close to the pre digging state as possible so that foragers will not veer off. Pitfall traps are left overnight.
Students come up with consensus prediction of which habitats will have the greatest number of different kinds of scavengers, which habitats the least, and must give reasoning for choices. Students will be looking for organisms that appear to have been attracted by the bait itself (beetles, flies as opposed to the spiders etc. of #90).
Discussion: Anyway, which habitat has the greatest diversity of scavengers? In which habitat would dead matter be most quickly removed (notice some but not too much convergence on #80)? What are the implications to the effects of habitat degradation? What use are scavengers and decomposers, anyway? Etc. etc.
Extension: An alternative would be to combine 90 and 91, putting paired traps at each site, one with bait and one without!
Question: Can you predict which habitats will have the greatest diversities of leaf litter arthropods? Do the most diverse faunas have the most complex web of interactions?
Season: All year.
Framework: III-11 (III-10).
Needed: Disposable aluminum piepans or some other sort of dishes of about the same size; Golden Nature Guides as necessary.
Notes: This is sort of like #91.
How To Do It: Students survey the grounds for various habitats to sample, then make predictions about which will have the most diverse leaf litter fauna, with explicit reasoning for said predictions.
Then each group of students (2 4?) use hands QUICKLY (so litter critters don’t duck out) to scoop up a big double handful of litter from a chosen site. As in 90 and 91, make sure that at least two samples are taken from each type of habitat chosen (i.e., two different sites). Students sit outside and sort through litter, exclaiming over each different type of creature encountered. Count the total number of different kinds, whatever they are, and what they do.
Discussion: Compare the species richnesses of the different samples and see if they conform to the prediction. Why are some sites richer than others in species? Does it have to do with the depth of the leaf litter? The absence of human disturbance? The amount of shading and moisture? The diversity of plants around or overhead? Or simply the closeness of the litter to the “natural” state?
Extension: If time and adequate materials exist, try to figure out the ecological relationships among the creatures: Which are herbivores, which are fungivores, which are predators, which are detritivores? Etc. Construct a “food web” if time permits. Does the complexity of interactions increase with diversity, or are more species of the same “trophic groups” or guilds simply added? How many trophic groups can you identify?
93. Spider Search
Question: Which habitats have the most species of spiders? Which have the greatest number of “functional groups,” or guilds, of spiders?
Season: Fall, late Spring.
Framework: III-11 (III-10, II-5-A).
Needed: Clipboard, paper, pencil, field guide.
Background Information: Handbook pages 55-58, Golden Guide to Spiders and Their Kin.
How To Do It: Here, for once students do not make predictions—they simply go out and see how many spider kinds they can find. Divide students up into teams, one team per habitat, and select at least four different habitats on campus to investigate.
Suggestions: do use the bare trampled part (may have wolf spiders etc.) and mowed lawn (may have sheet web weavers plus wolf and jumping spiders); don’t neglect planted hedges, palm trees, outsides of buildings (including eaves and gutters), inside classrooms, the flower garden, tree trunks.
Students count the number of different kinds of spiders encountered, and classify them into orb weavers, sheet web weavers, jumping spiders, wolf spiders, crab spiders, unknown.
Discussion: At the end of your field research, compare notes. Which habitats have the greatest number of spider species? Which habitats have the greatest number of spider guilds or functional groups? Is there a relationship? Are some habitats particularly rich in one functional group, others in another? How can you explain this? What seems to be the most important determinant of spider species richness: habitat complexity, shadiness, density of flies, number of plant species, or what? In what habitat are the most “pest insects” likely to be consumed by spiders? If you wanted to make sure that spiders were going to eat a lot of pest insects, how would you manage the habitat? Etc.
94. Goldenrod Complex
Question: How many kinds of insects use goldenrod flowers, and do different insects use different subsets?
Framework: III-11 (III-10, III-12-B, II-8-A).
Note: This is a much more specific version of #2.
Needed: Works great wherever goldenrod (Solidago) can be found blooming in the mid Fall.
How To Do It: Students simply go out and list all the kinds of insects that are feeding at goldenrod blossoms, noting the location of each insect as follows: Top, middle, or bottom branch of inflorescence; inner (near stem) or outer half of flower branch.
Make the activity comparative, by comparing isolated goldenrods with individuals in a large clump.
Discussion: How many kinds of insects use this single kind of resource? Are there more kinds in the dense clump than in single isolated plants? Do different insects tend to use different subsets of the flowers, and is their specialization consistent from plant to plant? Any possible causes? -- Are heavier insects on the lower, larger branches of the inflorescence, and are they on the inner half of each branch, more frequently than the smaller insects? Is this “resource partitioning” passive, or do there appear to be aggressive interactions? On stems with fewer kinds of insects, does the preference of a given insect kind become broader (that is, does the range of flower subsets used broaden in the absence of other insects)? Etc.
95. Barking Up the Wrong Tree: Isolation and Species Richness
Question: Do isolated trees have a less diverse bark fauna than trees in clusters?
Season: All year.
Framework: III-12-A (III-12-B).
Needed: One species of tree or large shrub, in which there is at least one isolated individual and at least one clump of three or more individuals.
How To Do It: Students tally the numbers and kinds of arthropods living on the bark of a given tree from the clump, and compare these tallies with tallies taken from isolated trees (by isolated, I mean isolated by at least 15 m).
Discussion: How do you interpret the results? How frequently do new insects arrive on the bark of a tree in a clump, versus on the bark of an isolated tree? Once an insect kind is established on a tree, is it there forever, or might it go extinct sometime due to some event or another? So, if insect populations on a given tree occasionally go extinct, but new ones more frequently on some trees than others, which trees will have more species at any given time? Now think about a whole forest, not just single trees. Which will have more species at a given time, a tiny isolated chunk of forest surrounded by parking lots or cattle pastures, or a big continuous forest? Explain.
96. Species-Area Curves: A Sweeping Statement
Question: In what manner does the cumulative number of species increase with area sampled?
Season: Fall, Spring.
Framework: III-12-B (III-12-A).
Needed: At least one sweep net (an extremely sturdy insect net, bought or home made, will do); plastic bags; Golden Nature Guide to the Insects.
How To Do It: Students elect a net sweeper, preferably the most hyperactive of the class; most are counters, while at least a couple (organized types, with good handwriting) are talliers.
One more or less uniform kind of habitat is chosen. The ideal habitat would be tall weeds at the edge of campus, but barring that, lawn that hasn’t been mowed recently would be okay; third choice would be a hedge of planted shrubbery.
The sweeper moves rapidly through/ along the sweeping habitat, sweeping the net hard back and forth against the vegetation. Every ten sweeps, the net is emptied into a plastic bag, which is then tied (air filled) with a Twist tie. Sweeper continues for long enough to give every “counter” her/ his own bag.
Counters are numbered from 1 on. First counter counts the number of different kinds of arthropods in her/ his own bag without opening it up, then moves on to #2, and #1 and #2 together figure out how many kinds of arthropods there are in bag #2 that are not already represented in bag #1.
Tallier(s) follow along keeping track of the cumulative number of arthropod kinds versus number of sweeps taken to that point. Teacher helps, obviously. At the end, using whatever kind of graph the students choose, a gigantic graph is made, with the X axis being bag number and the Y axis, the total number of arthropod kinds found thus far.
Discussion: Does the graph form a straight line? Does it look as if it’s levelling off? Are new species still added from time to time? Do you think these are rare or common species being added? What if the habitat sampled had enough room only for half the number of sweeps that were actually taken—how many different kinds of arthropods would there have been? Would some of the rare ones have been missing? Can you think of any real life analogues—which species will be lost first when a continuous natural habitat is chopped into tiny fragments? Etc. etc.
97. No Plant Is an Island?
Question: Does the number of kinds of arthropods increase with size of the individual plant?
Season: Fall, Spring.
Needed: Some plant that is quite abundant and that comes in a number of sizes, all of them accessible to students. This could be a weed or a small shrub (the latter is preferable). Also needed is a meter stick.
How To Do It: Students examine a wide range of sizes and shapes of this plant kind (make sure all shrubs are the same species). For each plant, simply count the total number of arthropod species on it, and take three measurements (height, E W direction, N S direction). Multiply the three measurements to get a very crude index to volume.
Discussion: Does the number of kinds of arthropods increase with plant volume? How might you explain this, and test your explanation? Graph plant volume vs. arthropod diversity. Does it form a straight line? Or does it look as if it’s levelling off? In general, which plants do you think would have more arthropod species, robust ones or little wimpy ones? Why?
98. It’s a Jungle Down There
Question: Does the number of kinds of arthropods increase with the size of a “moss jungle” island?
Season: All year.
Needed: Mosses. Most campuses, schoolyards, and many backyards have some patches of moss on exposed rocks, tree trunks, rotting trees, etc.
How To Do It: Students estimate the area of moss jungles of different sizes, and by peering carefully (magnifiers useful) count the number of kinds of arthropods. Graph the results.
Discussion: Does the number of kinds of arthropods increase with the area of the moss jungle? How might you explain this, and test your explanation? Does the graph of moss jungle size vs. arthropod diversity make a straight line? Or does it look as if it’s levelling off? Why? What if the moss jungles were twice as large as these are? Would there be twice as many different kinds of arthropods? What if these moss jungles were only half the size? Would some of the rare arthropods you found in your survey have been missing? Can you think of any real life analogues—which species will be lost first when a continuous natural habitat is chopped into tiny fragments? Etc.
99. A Little Disturbance Goes a Long Way
Question: Does an intermediate level of disturbance allow a greater number of species to coexist than either no disturbance or intensive disturbance, and why?
Season: Spring (Fall, Winter).
Needed: A not too frequently mowed area of campus (preferably, the most natural, unmanipulated habitat) and a students’ footpath going through it (unpaved, unrocked). Equipment: Meter sticks, and 50 cm x 50 cm “quadrat frames,” wooden frames that can be made by the school shop or that can be jury rigged from four meter sticks taped together; a string and a magic marker.
How To Do It: At five or more points along the path, the string is laid out at right angles to the path. The quadrat is placed on the ground, with one edge on the piece of string and the perpendicular edge right in the center of the path (see below).
The total number of different plant species included within the quadrat is counted. Then the quadrat frame is moved to the opposite side of the string, 50 cm along it (see diagram below). Again the number of plant kinds is counted.
Continue for at least four 50 centimeter increments. Repeat. If there are enough frames, then each group of students can do one transect—ideal. Compare the results.
Discussion: On a given transect, which quadrat has the fewest kinds of plants? Which the most? Do the most kinds occur farthest away from the path’s center, or at an intermediate distance? Now, which quadrat gets the heaviest disturbance? Which gets the least? Which gets an intermediate level of disturbance? Are the kinds of plants in the most disturbed and least disturbed quadrats the same or different? What kinds of plants does intense disturbance promote? In the absence of disturbance, what kinds of plants exist? Might they use up all resources and “out-compete” other species? Might slight disturbance decrease the success of the “competitive” plants and release some resources for other species? What if disturbance became too widespread, intense, frequent, or whatever? Can you think of any analogues in other places?
100. Diatom Succession