After a shower, the soil is soft and the animals which walked there, leave tracks. Bymeans of plaster, you can obtain the mould of these tracks and make an
interesting collection (figure 9). The experiment is very simple: it is a question ofbringing a little plaster in dry form, some water, a bowl to mix the plaster,
and a spoon to stir. But, to which animal belong the tracks you have picked up? From herestart the research of information. They exist books which give the picture of the tracksof many animals. Moreover, recognizing the animal which left the track is not sufficient:it is necessary to know something of its behavior, etc. From the simple collection oftracks you will be curious to know the animals of your land. Our article: "" provides you some indication on this topic. This experiment will openyour eyes so you can observe the territory around you when you walk in naturalenvironments with more attention. Plaster can be used also to obtain the mould of fruits,barks and other natural objects. From the cast you can also obtain the original shape.
The bottle garden is a close relative of the biosphere: a tiny garden growing inside abottle, a glass sphere, or a demijohn. The main difference is that soil is the maincomponent not water. The container can be kept sealed or opened like a terrarium. Ourswill be more for just plants whereas the terrarium may have animals. These gardens in abottle, can be cured and perfected as a system, they are also very decorative, in fact youcan treat them as a bonsai with not only a single tree, but whole landscapes. A carefullychosen stone becomes a rock, a small plot of moss represents a great prairie. A contorted,little plant is now a hundred year old tree. Maybe a marsh wetlands with peat moss,mushrooms and ferns is more to your liking. Maybe appropriate succulent plants with sandand rocks for a vast desert landscape. The choice is yours. There is no rigid rule aboutbeing either an open or a closed garden. It maybe useful to keep the lid on to retainwater. Or eventually, the plants grow up and need to hang down the outside.
If the container is always sealed, the challenge becomes quite demanding. In fact, it thenis necessary to obtain an equilibrium between plants and animals in order to keep aneffective cycle of substances and energy, but if this is difficult in a predominantlywater environment, it is even more difficult in a just moist environment. So, the gardenhas to contain a moist soil, plants, little animals like terrestrial isopods (i.e.: sowbug, pill bug), earthworms, etc. Plants have to be resistant to high moisture and have asmall size and limited growth. To avoid roots rotten, you can also try to refer tohydroponics and substitute the ground with small sized expanded clay or with gravel. Inthis case you will have more difficulties in hosting animal species, so it will have to beleft open. It is important you place your garden in a cool and well illuminated place, butaway from direct sunlight. Open or closed, a bottle garden is a fascinating thing, and theidea itself of a little and self-sufficient world is fascinating as well. There are peopleso fond of bottle gardens they work at them a long time, taking care of them using longand thin tools and to observe these environments till they imagine to be one of theirinhabitants.
Then choose among these main options:
1 - Opened bottle garden, containing moist ground, plants and possible little animals. Itis suited for people who love taking care of gardens and who have a flair for
the architecture of little wide spaces.
2 - Opened bottle garden, prepared in hydroponics and containing plants. It is suited forthose who tend to forget to water their plants.
3 - Sealed bottle garden, holding moist soil, plants, and some little animals. Thisexercise is suitable for people who are keen on biology and scientific research. They willhave to find appropriate plants and animals suitable for a sealed ecosystem and will haveto achieve the necessary conditions for a long survival. This research, bibliographic inpart and experimental, will keep students happily busy for long time.
The educational value of these little ecosystems is evident. They can be carried out evenin a school, where the teacher will be allowed to illustrate their characteristics topupils and encourage interesting discussions. In the web sites below, you will findimportant practical information in building your bottle gardens.
Terrariums : Miniature Worlds in a Bottle!
BBC online, how to gardening, bottle garden
Un jardin en bouteille
Le terrarium : Un monde miniature dans une bouteille!
Internet keywords: garden bottle jar, jardin bouteille bonbonne.
We exhale the carbon dioxide that plants need for photosynthesis.
Many scientists contributed to the discovery and understanding of photosynthesis throughout the ages; in this page are outlined some of those crucial milestone experiments that contributed to this effort.
Jan Baptista van Helmont, Flemish physician, chemist, and physicist, in the 1600s carried out a famous experiment by growing a willow tree in a pot for five years.
In this experiment Ingenhousz demonstrated that plants are dependent on light and their green parts for nutrients and energy.
For more photosynthesis experiments look here:
In its simpler form, this experiment is particularly suited to elementary schools.
1 - Put some beans in a little jar containing some moist cotton wool. Keep the jar closedto maintain the humidity. Every day pull out the cotton and observe the state of the seedsand measure the length of their roots.
2 - Students in junior high schools or high schools can try to evaluate the influence ofparameters such as temperature, light and nutrients on the speed of germination of theseeds. If seeds are placed in gelatin, it is possible to observe the germination withoutextracting them from the jar.
3 - You can also collect seeds of different plants and determine their vitality (percentof seeds which germinate) as a function of time to harvest.
Exploring Seed Germination
Germinating Seeds on Gelatin
The Great Seed Mystery For Kids
The Wonderful World of Seeds
Internet keywords: germination seeds student.
Drosophila, best known as vinegar fly or fruit fly, is the little fly you see flyingaround vinegar and on fruit during the fall. Why raise vinegar flies? To observe theirdevelopment, to observe the chromosomes of their salivary glands during division, toperform experiments on genetics, finally as food for amphibians that have just completedtheir metamorphosis. In this case it is necessary to breed a species that can't fly. Youcan obtain individuals with vestigial wings (wings which are not fully developed)at a university Biology or natural sciences department.
Culture medium recipe for drosophila: water 83 ml, agar-agar 0.8 g, sugar 5 g, brewer'syeast 10 g, alcohol 1.3 ml, nipagin
0.25 g. Nipagin M is used as a preservative in foods and cosmetics, like agar-agar, youcan buy it at the stores that sell science items for laboratories. Mix the yeast and thesugar, add agar-agar and water and simmer for 3 minutes. Turn off the heat. Dissolve thenipagin in alcohol and add to the rest when it has stopped smoking. Mix and let it set.
You can find other recipes at the following websites:
Aquick and simple introduction to Drosophila melanogaster
Fruit Flies - Drosophila melanogaster
Drosophila Culture (how to culture flightless fruit flies)
Observing the Development of Drosophila in Apple Juice Agar
Drosophila Genetics Lab I
A bibliography for an insect field biology course
La drosophile (in French)
Internet keywords: drosophila culture -cells, wingless fruit flies vinegar fly.
Until the end of the 17th century, people believed that little animals like flies andworms could spontaneously be born from substances in decomposition or from mud. FrancescoRedi, Lazzaro Spallanzani and Louis Pasteur made experiments which proved the idea of thespontaneous generation was wrong. At your home or in your school you can made suchexperiments too.
1 - Take two glass jars with a screw top. Put in each a little piece of cooked apple and aspoon of vinegar. For a night, leave one of these jars opened so it can be visited byvinegar (fruit) flies. Close the other jar with the lid and sterilize it by placing it inboiling water in a pressure cooker for a half an hour. After removing it from the cooker,let it cool, leaving it closed. The morning after, let the possible bugs present into thefirst jar leave and then close it with a fine gauze or a plastic sheet on which you willmake some pinholes to allow oxygen to enter. After a few days, you should see some bugs inthe first jar, and none in the second one. What has happened in the first jar which hasnot happened in the second? Some vinegar flies laid eggs in the first jar and from themsome new flies are born. In the second jar, even if there had been eggs, these are deadbecause of high temperature in the pressure cooker. More eggs were not laid because thejar was kept closed. With experiments like this one, you can realize that living beingscannot born from nothing, but they are born from other organisms like them. Fall is themore suited season to do this experiment because vinegar flies are particularly active.
2 - Anyway you can try to adapt this experiment to organisms present at other times of theyear. For example, if you place some dry grass in a water glass, in few days a deal ofprotists will appear. If instead you will put the same material in a close glass pot andif you boil it, nothing will be born. Only some rare thermoresistant microorganisms,bacteria which resist the high temperature of boiling water.
... Uhm, and still there is something which is not working: if any living being comes fromanother living being, from where has come the first living being from which all others arederived? Can we consider completely falsified the theory of the spontaneous generationwith these experiments? Is it possible to assert that, even if the spontaneous generationis not the usual way with which living creatures are born, at least at one time duringbillions of years it has happened on the Earth or another place in the Universe? It is noaccident that there are scientists who study how life began in the first place.
Internet keywords: spontaneous generation.