These are among the experiences the most significant education and often criticized or cited as a trauma, dissections are nonetheless a remarkable observation exercise the many pedagogical virtues. In these four articles entitled "chronic dissection" I shall return to these farm animal biology L2 UPPA.
TP3: The Green Frog.
pre-copulatory Guarding and sexual dimorphism.
The kind of day is the green frog, Rana esculenta
is the most common frog in France. It occurs often àproximité ponds and shallow shorelines of ponds, they rarely nequittent unlike many other amphibians quimènent most terrestrial life.
Rapid morphological study allows to évidenceun sexual dimorphism more or less marked. In addition to size (the male is smaller than the female souventplus), a first character is the presence of vocal sacs behind Labouche that allow strong voice and capable of varied plusbelle upset the female frogs!
Once the beautiful charmed the male will userd his second secondary sexual character: rough callus del'index (only 4 fingers on the front, the thumb being dropped) permettantde him cling to his back rolling Annual partner. It goes well resteraccroché on the back of the female (
amplexus pictured right) until it Ponde unchapelet oocytes generally tangled in the water around the shoreline plants. Fertilization is external and that's sure to be the one to fertilize the eggs that the female mâles'agrippe. This is a pre-copulatory guarding Exampleof (mate-guarding), a key step that corresponds to lareproduction a form of sexual selection. Indeed seretrouvent males compete for access to females and the most fruitful lesplus close to spawning. Vice versa for a female copulatory gardiennagepré-long is a guarantee of quality male and therefore a deselection form (in addition to singing).
[The vocal sacs (left) and the callus on the finger No. 2 (right) males. The callus is observed that during dereproduction, coloring may also vary greatly.
Opening of the oral cavity
One difficulty of the dissection is enl'ouverture of the oral cavity in order to separate the digestive tract etaériennes. To complete this stage it is first necessary to bienprendre his bearings, then describe the oral cavity. The floor of the mouth secaractérise especially by a forked tongue very sticky. At rest this langueattaché front of the mouth is folded back, but it is projected volontiersvers forward (pro-tractile) to capture a beautiful dragonfly. In the male onobserve holes of vocal sacs. At the very bottom floor of the mouth in régioncentrale, glottis forms a longitudinal slot, which opens on lelarynx, quidonne access to the lungs (airways). The maximum oral entouréd'une toothed jaw includes choanae (internal orifice of the nostrils), desdents vormériennes, and finally the holes Eustachian tubes, which are communiquercavité oral and middle ear. Finally, between these two parties, Lepharynx, comes in the form of a very large hole transverse quiprécède the esophagus (digestive tract).
Once tracking is accomplished, we must first identify lespoumons well, separating them without damaging them too lobe of the liver, then del ' esophagus so as to keep them with your fingers folded on leplancher mouth.
should then with scissors strong cut mâchoired'un side, then so trèsprogressive few mm each time, cutting the floor of the mouth and pharynx laglotte between the scissors (do not hesitate to descend to the bottom beyond the mouth, well below the glottis). Of course, laglotte and lungs should remain attached to the floor of the mouth and ladissection! It convientensuite not complete the cut to close the floor of the mouth on Lecot.
[And here's the result: floor of mouth with the left lung,
Oral and ceiling right with the esophagus. ]
The art of pinning
To submit a dissection, a point estessentiel: pinning! Lesépingles head should always be arranged in very oblique to nepas restricts movement, and the inclination should always be versl'extérieur dissection. In this way the tissues are pinned mieuxmaintenu (a bit like sardines in a tent). Lesépingles more then a star arrangement around which the dissection nemasque not the view.
Pinning of the intestine in the frog is a redoutableexercice. It is indeed the place and pin it to sanspour As much tear the mesentery that attaches to the gut cavitégénérale. Some tips for success:
- Unwind with your fingers and observe a very courteportion of the intestine (1 cm) without tearing the mesentery. We do not do ensuiteque this portion, the course is progressive!
- Form a loop on that portion encontournant place a pin which supports. This pin will not crash, it just serves to fold the intestine to make it describe the ontveut loops (which are not natural curls).
- Finish pinning the loop a little arrièrede the first hairpin, the end loops, therefore, measure 0.5 cm environet touch each other.
last trick, a small black paper placed here where làpourra highlight structures and constitutes the clearest unebonne aid to observation.
And here as usual the poster of the dissection completed. The next and last column announcement: the mouse.
Sources:
- Wikipedia Rana esculenta
Sexual selection - site DORIS: http://doris.ffessm.fr/
- Lab Animal Biology - Zoology Embryology Histology, 3rd edition. Andrew Beaumont, Pierre Cassier. Editions Dunod 502p.
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First breeding mouse is economical, with low volume occupied, and a consumption of 5 g of food per day only. More lareproduction is easy and fast with 5 to 15 litters per year, each donnantnaissance a dozen mice or mice parfemelle fifty year! This ability to reproduce rapidly unedurée associated with short life is a strategy r : it's actually a glibness offset by the number one natural mortality (predation, starvation etc..) Important. It contrasts this strategy to the strategy K (long life, large animals, breeding in small numbers). 
Another glands of the gut is the pancreas quilibère pancreatic juice rich in enzymes of all kinds - proteolytic (trypsin, chimotrypsine, carboxypeptidases)-glycolytic (α-amylase), lipolytic (lipase). Mice is a body bounded diffusmal present in the mesentery after the stomach. 
Once the beautiful charmed the male will userd his second secondary sexual character: rough callus del'index (only 4 fingers on the front, the thumb being dropped) permettantde him cling to his back rolling Annual partner. It goes well resteraccroché on the back of the female ( amplexus pictured right) until it Ponde unchapelet oocytes generally tangled in the water around the shoreline plants. Fertilization is external and that's sure to be the one to fertilize the eggs that the female mâles'agrippe. This is a pre-copulatory guarding Exampleof (mate-guarding), a key step that corresponds to lareproduction a form of sexual selection. Indeed seretrouvent males compete for access to females and the most fruitful lesplus close to spawning. Vice versa for a female copulatory gardiennagepré-long is a guarantee of quality male and therefore a deselection form (in addition to singing). 
The Church is not that the church of Rome, but all the churches that recognize Jesus as the mark of God in human history and teach the gospel. Among these churches are the Church, one of which is dear to the Celts and is the root of France, I called the Gallican church, faithful to the oldest tradition and yet open to modernity. His priests may marry, for example. To find the church in Alsace, appointment Saturday, November 13, 2010 in the Lutheran Church of Wolfisheim to 18 hours, on the occasion of the feast of St. Alphonsa of Gazinet. 
A Compostela Holy Father has rightly highlighted the dangers facing a de-Christianized Europe, but in Barcelona in sanctifying the horrors of Gaudi, and facing the homosexual provocation, he failed to consider the responsibility of the church in that de-Christianization. 
If you visit the Isle of Man between England and Ireland, perhaps you will encounter 'the little people', the little people of elves and other nature spirits that are said they inhabit certain places. Student in England in 1958, I remember crossing a stream on the island of Man on a small bridge with a bearded native said with a straight face not to mention not to disturb the little people, which he , lived under the bridge. 
