1.7.1.6 Biologie
Get flash to fully experience Pearltrees
Le logiciel simule le travail d’une cytogénéticienne lors de l’établissement d’un caryotype, c’est à dire qu’à partir d’une image de cellule en division, l’ordinateur classe rapidement l’essentiel des chromosomes et ne laisse plus à l’élève que quelques chromosomes à classer. En quelques clics, l’élève va alors pouvoir vérifier si il a bien compris le principe du caryotype. Ensuite, un autre caryotype à faire est proposé puis un troisième qui présentent tous deux une anomalie chromosomique qui va mettre l’élève devant une difficulté à résoudre... caryotype (Flash de 231.5 ko) caryotype (Zip de 1 Mo)
Un caryotype en quelques clics.- Sciences de la vie et de la Terre - Pédagogie - Académie de Poitiers
Google Earth phylogenies
Now, for something completely different. I've been playing with Google Earth as a phylogeny viewer, inspired by Bill Piel's efforts , the cool avian flu visualisation Janies et al. published in Systematic Biology ( doi:10.1080/10635150701266848 ), and David Kidd's work . As an example, I've taken a phylogeny for Banza katydids from Shapiro et al. ( doi:10.1016/j.ympev.2006.04.006 ), and created a KML file. Unlike Bill's trees, I've drawn the tree as a phylogram, because I think biogeography becomes much easier to interpret when we have a time scale (or at least a proxy, such as sequence divergence).
There are several pre-computed trees available for display, including the main Tree Of Life, described in Ciccarelli, et al., 2006 . In addition to the precomputed trees, you can upload and display your own trees and data, using the 'Data upload' page or through your personal user account . Use the tabs on the top of the page to navigate or click the tree below to proceed to the interactive Tree of Life page. Extensive help pages , which provide detailed explanation of iTOL's interface and functions, are available. For further questions, comments or suggestions, please contact us .
iTOL: Interactive Tree Of Life
Cells are divided into two main classes, initially defined by whether they contain a nucleus . Prokaryotic cells (bacteria) lack a nuclear envelope ; eukaryotic cells have a nucleus in which the genetic material is separated from the cytoplasm. Prokaryotic cells are generally smaller and simpler than eukaryotic cells ; in addition to the absence of a nucleus, their genomes are less complex and they do not contain cytoplasmic organelles or a cytoskeleton ( Table 1.1 ). In spite of these differences, the same basic molecular mechanisms govern the lives of both prokaryotes and eukaryotes, indicating that all present-day cells are descended from a single primordial ancestor. How did this first cell develop? And how did the complexity and diversity exhibited by present-day cells evolve?
The Origin and Evolution of Cells - The Cell - NCBI Bookshelf
Timeline of Discoveries | The Leakey Foundation
In the American Institute of Philanthropy’s view, 60% or greater is reasonable for most charities and the most highly efficient charities are able to spend 75% or more on programs. From the AIP website : "AIP is a nationally prominent charity watchdog service whose purpose is to help donors make informed giving decisions."
DNA is extracted from human cells for a variety of reasons. With a pure sample of DNA you can test a newborn for a genetic disease, analyze forensic evidence, or study a gene involved in cancer. Try this virtual laboratory to perform a cheek swab and extract DNA from human cells. PCR is a relatively simple and inexpensive tool that you can use to focus in on a segment of DNA and copy it billions of times over.
Learn.Genetics™
Stem Cell Information Home Page
Stem cells can develop into different cell types. They may offer a renewable source of replacement cells to treat diseases, conditions, and disabilities. On March 9, 2009, President Obama issued Executive Order 13505, entitled "Removing Barriers to Responsible Research Involving Human Stem Cells."Understanding Evolution
glossary | home | Take our site tour , find out what's new , or subscribe for updates . Climate change causes loss of genetic diversity - April 2012 If you'd visited Tuolumne Meadows in Yosemite National Park 100 years ago, you probably would have encountered the alpine chipmunk, Tamias alpinus . Today, however, park visitors will have to hike up a nearby mountain to see one of these critters.
Cellule
WebGL not supported To ensure fast performance and prevent crashes, some browsers that support WebGL deactivate it for particular video driver and operating system versions. (For some browsers it is possible to override this -- you can manually turn WebGL back on by changing a setting. Do so at your own risk.)
