Photosynthesis experiments for high school scholarly …
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.
high school biology 4 photosynthesis bscs Study Sets …
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.
A lot of organisms emit light. Of course you know fireflies, but there are also otherluminescent organisms such as some fishes, mushrooms, bacteria, dinoflagellates, andshellfishes. The culture of luminescent bacteria is not difficult. What you have to do isto get a strain of luminescent and harmless bacteria and raise it in a suitable culturemedium. A bacterium widely cultured and used also for lessons in schools is the Photobacteriumphosphoreum, now renamed: Vibrio phosphoreum.
Search for information about the mechanism of the bioluminescence. You can findinformation for this culture and general information on the Internet at sites listedlater. There is a lot of information on bioluminescence on the Internet. There are evenamateur sites devoted to this topic. You can buy the Vibrio phosphoreum at commercially,such as the ATCC (American Type Culture Collection) .You can find other firms of this type on the Internet, using the keywords: culturecollection. Also try the links for the protists experiment. These companies also supplythe culture media and in their sites you can often read their composition.
: In these experiments, need thehelp of a biologist to avoid culturing dangerous microorganisms. Even with help, keep thecultures only for a short time, wash your hands, wash and disinfect all tools which havebeen in contact with the cultures.
Utilisation Pedagogique de Bacteries Luminescentes (in French)
Bioluminescence in Plankton and Nekton (there is a list of luminescent organisms)
Flash! Bacterial illumination
Isolation of Pure Cultures Of Bacteria (Please, read the safety warnings present inthis website)
Bioluminescence Web sites
Internet Keyword: luminous bacteria luminescent bioluminescence luciferin luciferase.
To find companies which sell strains of microorganisms use the keywords: culturecollection.
Are the insects which fly around lamps at night attracted by light or heat? To find out,use a clothing iron and an electric lamp. The electric lamp produces light with a littleheat, the iron produces only heat. Put both on a table. Keep them at least a meter (abouta yard) apart and with the emitting surfaces turned away from you. Note the differentbehavior of insects. Mask the lamp with plastic sheets of different colors and verify ifbugs are more attracted to a particular color. This is also a method to capture nighttimeinsects, particularly moths, so you can observe them with a lens or a stereoscopicmicroscope.