Ana səhifə

Schoolyard nature study activities for ecological education in florida backyards and schoolyards


Yüklə 394.41 Kb.
səhifə3/11
tarix15.06.2016
ölçüsü394.41 Kb.
1   2   3   4   5   6   7   8   9   10   11

Discussion: What could be eating these? Might there be different fruit consumers in different seasons? Why might different plants fruit at different times? Are there any consistent trends, across species, in the traits you’re monitoring with season? How do fruits available to fruit eaters (birds and sometimes small mammals) change over the seasons, and why? What’s going on? See pages 34-37 of the Handbook.

19. Plastic Plants

Question: Do plants growing in different habitats allocate different proportions of their energy to reproduction, and why might this be so?

Season: Spring, Fall.

Framework: I-3-A-i (I-2-A, I-3-C-i).

Needed: A flowering or fruiting “weed” that grows in different places, for example mowed and unmowed patches, sparse vegetation versus a dense hedge, or sun and shade. Many possibilities species to be used. What are leaves used for? What might be the benefit of diverting energy to leaves? What about flowers, later fruits? What about roots? What about stem—what earthly use is it, anyway (encourage students to come up with idea that stem is a way of getting leaves—and flowers/fruits—up high enough to do some good, i.e., so leaves are in full sunlight and above “competition,” so flowers and fruits are accessible to animals. Recall that plant has only certain amount of energy to spare, and can’t enhance all four uses simultaneously.

How To Do It: Make the introduction very short, though, because after choosing two obviously different habitats to sample, students go out and “randomly” collect individuals from each. Gather at a picnic table and examine the plants.

Discussion: Does the amount of energy allocated to stem increase in habitats where there’s thick weedy vegetation? Why might this be so? What about shaded forest? Or do shade plants have more, or larger, leaves than sun plants? Or larger but fewer leaves? Or smaller and fewer? Most important, though, is reproduction. What proportion of energy is allocate to reproduction versus other functions? Why?

Finally, do you think that plants are “born plastic” and go one way or the other depending on environment, or do you think that plants growing in different habitats have fixed sets of traits? How would you distinguish between the two proposals?



Extension: To get a better estimate of energy allocation, rip the plant apart into its four components (reproductive structures, roots, stems, leaves), and make little piles. Compare sizes of piles. Much better yet, weigh each little pile (but do not pool piles from separate plants—why not?).

20. Perilous Pollen

Question: Who knows what evil lurks in the hearts of flowers? “Not I,” said the bee. “Not I,” said the butterfly. “I do!”, said the student after 45 minutes of active searching among a common early Fall flowering plant.

Season: Fall (although this can be done with Catalpa , Hawthorne, Cherries, Redbud, and a few other plants in Spring).

Framework: II-6-B (II-5-B, II-5-A, III-3-A-i).

Needed: Pencil and paper; sunny day with lots of flowers.

Background Information: Here’s the chain of reasoning: Most flowering plants need sex. Sex involves pollination, often involving pollen moving from one plant to another of the same kind. But plants can’t move around and get sex for themselves. Many dump their pollen on unsuspecting animals seeking food.

What provides the food? The flower, either in the form of nectar or “extra” pollen. So, flowers are “targets” advertising free food for foraging freeloaders, and many animals travel from plant to plant blissfully unaware that by carrying a little yellow “dust” they’re helping plants to reproduce

Well, if animals are predictably arriving at these colorful little targets called “flowers,” aren’t these good places for animals that eat those animals to hang out? Of course. And if the lurking predator were conspicuous in color shape, might not the potential flower visitor veer away? Of course. So, what do you expect to find? Some expert flower lurkers that blend in to, or hide behind, the flowers awaiting innocent plant matchmakers.

Indeed, a careful scan of goldenrod (Solidago), Monarda mints, or Spanish needle (Bidens) flowers in Fall will reveal an occasional monster in the form of crab spider, green lynx spider, or ambush bug (along with a very occasional jumping spider or praying mantis). Crab spiders and ambush bugs are often highly camouflaged; lynx spiders and the others often hide behind flowers and leap out (see Handbook page 58.



How To Do It: So, students roam around yelling and screaming when they find something neat. If they are lucky they may find a lurker in the very act of munching on a pollinator. Often wings or other body parts are littered under the flower a lurker occupies. Have students look for these signs too.

At the end, have students compare notes and look at each other’s discoveries.



Discussion: Does each lurker blend in, or do some hide and leap? What are some special traits of lurkers related to their life style? What would happen if lurkers were more numerous—might pollinators learn to avoid the flowers? What might be the effect on a plant of having a resident lurker? Negative effect? What if plants have klutzy lurkers that often attack pollinators unsuccessfully, scaring them off? Might this actually benefit the plant? How?

21. Turk’s Cap, Toothpick, and Sulphur

Question: Can you do a better job than butterflies at pollinating a flower?

Season: Fall (sometimes well into Winter); best around October.

Framework: I-3-A-i (II-6-B; II-6 *).

Needed: Hand magnifiers (the generic type mentioned in the introduction are fine); twist ties (the kind that come with plastic bags) of two colors; and Turk’s cap (Malvaviscus arboreus), a common ornamental in our area, is the ideal flower for this (it occurs around at least 30% of schools, or if not on campus, then at least nearby).

Note: This activity uses Turk’s Cap Hibiscus, but it’s possible to do this kind of thing with many other flowers, especially large ones. This plant is used here because it has large flowers with large flower parts, and it’s not native or naturalized.

Background Information: Turk’s cap has huge pollen grains that are visible even to the naked eye. They’re produced in anthers wrapped around the style, or “column,” that supports the stigma, or female surface that is the only place where pollen grains can germinate and fertilize the flower. Unless something or someone moves the grains to the bristly five lobed stigma, no fertilization will occur and no fruits will be produced.

In some cultivated varieties, not only must pollen be moved, but also pollen must be moved from a different individual plant, as commonly occurs in plants; in other cultivated varieties, pollen can fertilize stigmas on the same plant, even the same flower, but it still has to be moved. The pollen is sticky and doesn’t move in the wind.

In its native haunts in the New World tropics, this plant attracts hummingbirds to its flowers; while drinking nectar from the flowers they knock their foreheads against the anther  and  stigma mess, inadvertently moving pollen about. Here, though, those hummingbirds are missing, and about the only things to visit flowers are cloudless sulfur butterflies (Handbook pages 80-81), which also suck up nectar.

How To Do It: So: after a brief discussion of pollination and of the plant’s origins, students scurry around examining flowers with magnifiers, looking for pollen grains.

Watch butterflies on flowers (don’t worry, they’re always present in mid afternoon in Fall). How do they feed? Do they hover in front of the flower, contacting the reproductive parts? Or do they land on the flower and slip the “tongue” in from the side? Do they foil the plant’s nefarious food for sex scheme? Why?   are they trying to be nasty, or do their behaviors and constructions lead to this circumvention?

Next, examine lots of stigmas in mature flowers. See any pollen grains adhering? adhering to top in particular?

Finally, arm students with toothpicks. Each student gets to be a purposefully “nice” hummingbird, scraping anthers on one flower to load the toothpick with pollen, then dabbing the pollen against the stigma of another flower. Half the students are “lazy hummingbirds,” moving pollen only from one flower to another on the same plant; the other half are “hyperactive hummingbirds,” moving pollen from anthers on one plant to stigmas on another.

See how many grains you actually transferred, and compare with the numbers on untouched stigmas. Tie one color of twist tie around flowers pollinated by lazy hummingbirds, the second around flowers pollinated by hyperactive hummingbirds, and the third around an equal number of flowers left alone.

Which group of flowers do you think will produce the most fruits? the fewest? Every week thereafter, students quickly examine twist tied stems for evidence of developing fruits. When developing fruits are obvious, discuss the results.



Discussion: How can Turk’s Cap exist at all in Florida, if it never produces seeds? What’s responsible? What might lead a plant to be specialized on one kind of animal for pollen movement? What does this example tell you about the perils of being specialized? What if a whole bunch of plants, dependent on pollinators, suddenly lost their pollinators because pesticides were over used nearby? Etc.

22. Buzz Off

Question: Does partridge pea (Cassia) release the most pollen only when a bee buzzes the correct password, and why?

Season: Fall only (no equivalent flower at other seasons).

Framework: I-3-A-i (II-6-B).

Needed: Glass microscope slides, but white (better, black) paper squares about 25 mm (l inch) square would do just fine; a set of tuning forks of different pitches (available from music teacher or band leader??), or one adjustable tuning fork; some partridge pea (Cassia) (see field guide entry, more or less done); hand lenses useful but not absolutely necessary.

How To Do It: First, very short discussion of pollination; mention that some animals, especially bees, consume pollen as well as nectar. Mention that many different kinds of bees visit flowers, from very small to quite huge (for an insect). Mention that non flying bees can make a loud buzz by vibrating the muscles that power their wings; different kinds of bees make buzzes at different pitches.

Now, after no more than 5 minutes, examine the field of partridge pea. Watch bees foraging. What do the bees do? Do they hang on and buzz? Do different bees buzz at different pitches? Can you see pollen spewing out? Are the bees drinking nectar? Look at an anther with a hand lens and see if you can see the tiny hole through which pollen squirts. Now, try yourself with tuning fork; one student holds the slide or paper just barely touching the tip of anthers, the other student strikes the tuning fork and then barely touches the vibrating tip to the anthers (this may take a couple of minutes of practice). Does pollen come squirting out?



Discussion: Hey, what’s going on inside the anther? Do different tuning forks stimulate different pollen volumes? Obviously, each new try should involve a new flower, but it’s unlikely that a flower’s pollen would be exhausted by one buzzing bee (or tuning fork) visit: what if the flowers dumped all their pollen on the first bee to come along, who just happened to be a worthless vagabond with an avowed intent never to visit another partridge pea? or what if a perfectly decent bee visited the flower, was dusted with all its pollen, and then got nailed by a crab spider (see above) on its very next visit?

23. Sociable Seedy Plants

Question: Do sociable plants produce more fruits per flower than lone wolf plants, and why might this be so?

Season: Any, depending on plants.

Framework: I-3-A-i (II-6-B; I-2-B; I-4-C).

Needed: A widespread flowering plant in fruit (or in seed) that carries evidence of how many flowers each inflorescence originally held. Examples: Lantana camara, possibly vetch (Vicia) and partridge pea (Cassia), laurel cherry (Prunus caroliniana), etc. Pencil, paper, and eraser.

How To Do It: Find a widespread flowering plant in fruit (or in seed) that carries evidence of how many flowers each inflorescence originally held. Look for plants in each of both situations: sociable plants, or plants growing very near a cluster of others of the same kind; lone wolf plants, or plants growing quite alone.

On at least three inflorescences of each plant, make two counts: number of developing fruits; and original potential for fruits (i.e., number of developing fruits + number of scars from presumably unfertilized flowers. Make these into fractions, and then convert these fractions to percentages.



Notes: Another alternative is to count the first 100 original flowers (scars + fruits) and note how many of those have fruits.

Discussion: Anyway, compare. If you found a difference, why? If you were a weak flying animal flower visitor, would you seek food at isolated spots, or hang out in the fast nectar strip? If you didn’t find a difference, what does that tell you? strong flying pollinators that aren’t deterred by distance? perhaps pollinators aren’t required for fertilization? Other alternatives?

24. Shady Deals

Question: Do sun loving pollinators spurn shady plants and lower their seed production?

Season: Any, depending on plant.

Framework: I-3-A-1 (II-6-B; I-2-A).

Needed: Fruiting (seeding) kind of plant with representatives in full sunlight and other in at least partial shade.

How To Do It: Basically same as above, but capitalizing on the fact that many flower visitors can be easily seen to prefer flying in sun to flying in shade. This is especially true for butterflies, for example those that visit Spanish needle or lantana. Begin outside: if any individuals of the plant in general are still in flower, watch butterflies. If no individuals of the species in question are in flower, just watch butterflies period. Question: do butterflies fly more in shade or sun? Using these observations, students predict which plants will have greater per flower fruit or seed output, sun or shade plants. Compare as above (again, easiest might be to count to 100). Which sets more seeds or fruit per flower? Can you relate this to your butterfly observations? Are there other possible explanations (e.g., energy limitation in shade plants; increased predation rate in shade; etc.)?

25. Sex and the Single Bug

Question: Which insects mate on flowers in the Fall, which don’t, and why?

Season: Fall.

Framework: I-3-A-ii.

Needed: At least some flowering goldenrod (Solidago) or other flowering plant (some clovers (Trifolium), Monarda mint, etc.) loaded with mating pairs of lovebugs and/or soldier beetles.

Background Information: For a female insect to reproduce, she must mate sometime previously. Different insects breed at different times and in different places. Male and female insects must “find” one another in order to mate; so many use chemical signals to do this, others simply aggregate at certain sites.

How To Do It: Then, students search through goldenrod (Solidago) patch (or other), noting which kinds of insects are mated and which kinds aren’t. Observe mated pairs carefully; what are they doing? Pull a few pairs apart to see the different sexual apparatus of male and female; might this explain why they pair up for so long? Why might a male remain attached to a female whom he’s already fertilized (are there any bachelors around?)?

Are the flowers acting as “singles bars”? How can you tell? Why might the mating insects be congregating there? What about the other insects that are (momentarily) chaste? Where and when do they mate? Why don’t all insects use goldenrod for mating? Etc. etc.



    Alternatives?

  • Observe lekking Velvet ant males in sandy spots (they look like really fuzzy wasps). Can you find the female?

  • Follow hilltopping butterflies (if you can find a hill). Are there lots of males? What happens when a female appears? How does their behavior differ from males’?

  • Watch male Red Admiral or Question Mark butterflies who have staked out a plot. Try standing in their favorite perching spot and see if they’ll land on you!

  • Join anoles doing pushups. Paint your fingertip red underneath and imitate the headbobs. How does the lizard react?

  • Try to map a mockingbird’s territory. They sing in towards the center of their territory from the outside instead of outward from the center as most birds do.

  • Study dragonfly territoriality and mating. Dangle a test dragonfly from a pole and see how the neighbors react).

    If you ever find a newly-hatched female silkmoth (look for big silky golden cocoons), place her on your window screen. Leave with the window open and see who comes to visit that evening. How did he find her? Why might those antennae be so fuzzy?

26. Sticky Seeds

Question: How and why do some seeds stick to your fuzzy socks?

Season: All year.

Framework: I-3-B-i (I-4-D).

Needed: Some cheap adult cotton tube socks that come up as close as possible to students’ thighs; wool would be ideal, but probably an unlikely item in north Florida. A weedy edge on campus.

Background: See the Handbook pages 13 and 41-42.

How To Do It: Have students pull the socks up over their entire foot (with the shoe on) and lower leg. Have most students walk through a weedy thicket, but have a few walk across mowed lawn; if a woods is available, have at least two students walk through there. If it doesn’t look as if they’re picking up many burrs, have them walk back and forth, on slightly different paths, several times. Then assemble at a picnic table, pull off the socks, and see what you have.

Discussion: How many different kinds of burs are there? Are there more burs in the weeds than on the lawn (or in the forest)? Why? Especially, why are there more burs in weeds than in the forest? What purpose does a bur serve? What are the different traits of different bur species (magnifiers are useful here)? Do different kinds deposit their burs at different heights? Why? Go back and look at the plants the burs came from. Do some burs stick tighter than others? Can you tell how? What might be some consequences? Would you expect to find many bur species in shady forests? Compare burs with fleshy fruits as alternative means by which plants get their offspring out of the house.

Question: Do the mechanisms that plants employ to disperse seeds vary with habitat, and if so, how?

Season: Fall (Winter, late Spring).

Framework: I-3-B-i (III-13).

Needed: At least two habitat patches on campus, hopefully more. Pencil and paper.

Background Information: Begin with a quick Discussion: seeds travel away from mother (a) in the wind; (b) by dropping and perhaps rolling a bit; © by floating; (d) by sticking to animals; (e) by travelling in, or being discarded by, a fruit eating animal; (f) by exploding into the air. See Handbook, page 13.

How To Do It: Then, students go to weedy hedge or unmowed lawn edge and try to figure out the seed dispersal mechanism of each kind of plant there. Tally the number of species in each category. Then, go to other habitats (shrubby area; mowed lawn; woods edge or interior, if available) and do same.

Discussion: Do the habitats differ in the number of species in each category? Where are most wind dispersed seeds in the small plants? Did you see any wind dispersed trees? Might wind dispersal have to do with being in the top and most wind swept layer of vegetation, whether that’s the canopy of a forest or the “canopy” of a weedy field? What about droppers/ rollers? Do you think they’d be the first to invade a newly plowed field some distance away? Where are burs most prevalent (see #26)? What about fleshy fruits?

Speculate on the biology behind every trend you see, and how you might go about testing these. In what habitat is a large seed most necessary to help the seedling along in its growth? So, given a large seed, is the plant likely to have wind dispersal? Drop and roll dispersal? Water dispersal? Bur dispersal? Or fleshy fruits? Etc.



    Extension:

  • It’d be great if you lined up the different dispersal units from the different habitats, so the students can see the diversity.

  • If you’d like to see what kinds of plants grow from the burs, you can wet the socks and “plant” the seeds. Watch to see what kinds of plants grow.



28. A Galling Experience

Question: Why are there so many kinds of plant galls, and why isn’t any one kind more common?

Season: Spring (Fall is okay for some, especially goldenrods). Also Winter, but most galls will be empty.

Framework: I-3-B-ii (II-5-E, I-4-B, I-4-C)

Needed: Special requirements include magnifiers, a sharp knife, the Golden Nature Guide to Insects, or even better, the Peterson Field Guide to Insects.

Background Information: See the Handbook pages 10-11, 22, 24, and 25.

A gall is a hollow lump or hollow ball on plant leaf, petiole, or twig, produced by insects and used by them for home, food, raising young. Many insects produce galls: these include flies, aphids and relatives, wasps. Some galls are inhabited by a single insect (that hatched from an egg laid by the mother), other times by a huge brood of offspring (sometimes with mother too).



How To Do It: First, go out and find a gall. Galls are common on goldenrods (Solidago), leaves and twigs of oaks (Quercus), leaves and stems of hackberries (Celtis laevigata), leaves of hickories (Carya), bays (Persea), leaves of many other trees and shrubs, and on the stems and leaves of some herbs.

Once the first gall is found (a prize for the finder?), the teacher carefully opens it with a knife. Anyone home? If so, who? If not, what evidence is there that someone was home in the past (look for insect “skins,” etc.).

After brief discussion, send the class on a “treasure hunt,” with prizes for finding the most plant kinds with galls on them and finding the most kinds of galls on a single plant. Open all galls up and scrutinize them with hand lenses. Compare. Look at the tissues in the different parts of the plant that harbor galls.

1   2   3   4   5   6   7   8   9   10   11


Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur ©kagiz.org 2016
rəhbərliyinə müraciət