Duration
30h Th
Number of credits
| Master in biology of organisms and ecology (120 ECTS) | 5 crédits |
Lecturer
Language(s) of instruction
French language
Organisation and examination
Teaching in the first semester, examination in June
Schedule
Units courses prerequisite and corequisite
Prerequisite or corequisite units are presented within each program
Learning unit contents
[UPDATED IN 2022] The comparison of molecular sequences has been extensively applied to the enigma of the evolution of eukaryotes. For ten years, the trees obtained from the rRNA of the small subunit of the ribosome suggested that most eukaryotes had emerged simultaneously (crown group phylogeny), whereas a few lineages of "protists" would have branched earlier. As these basal lineages appeared mainly composed of parasites lacking mitochondria (e.g., microsporidia), the prevailing hypothesis was that these "Archezoa" actually appeared before the acquisition of the mitochondrion -- which is the result of the endosymbiosis of a bacteria within one of these amitochondriate proto-eukaryotes.
However, at the turn of the millennium, a converging body of evidence eventually convinced phylogeneticists that this tree was incorrect and that Archezoa -- if they had ever existed -- had disappeared today. Among these indices were the finding of degenerated mitochondria (hydrogenosomes and mitosomes) as well as the presence of genes of mitochondrial origin in the nucleus of the so-called Archezoa. Regarding the topology of the rRNA tree, it could be explained by phylogenetic artifacts that wrongly reject fast-evolving species at the base of the tree.
More recently, the advent of phylogenomics (i.e., the comparison of hundreds of genes simultaneously) led to great progress in resolving the tree of eukaryotes, such as grouping nearly all lineages first into six then only four super-groups (Unikonta = animals, fungi and amoebas, Archaeplastida = plants, SAR and Excavata).
In this course, students will be effectively introduced to the phylogeny of eukaryotes and to its wanderings through the writing of a personal critical review of the phylogenetic literature, bearing a historical perspective.
Learning outcomes of the learning unit
At the end of this course, students will be aware of the difficulty to infer the evolution of eukaryotes and eukaryotic lineages, in particular because of phylogenetic artifacts. They will be able to present, argue and contrast the different phylogenetic frameworks proposed during the last 30 years and to cite the key authors, especially for some lineages of interest.
Prerequisite knowledge and skills
It would be better to have a working knowledge of the diversity of Life, including "protistology" (e.g., algae and fungi), and molecular phylogenetics: Biodiversity and ecology [BIOL0518-1], Microbiology [MICR0715-2] and Phylogenetic methods [GENE0448-1].
Planned learning activities and teaching methods
If several students are interested in the course, different subtopics will be defined by the parties to avoid duplicate efforts. Hence, one can choose to study the phylogeny of a specific eukaryotic group (e.g., arthropods, lichens) or to discuss an evolutionary concept in particular (e.g., living fossils, secondary simplification). Whatever the topic at hand, the historical perspective (evolution of ideas) shall be at the heart of the work.
About twenty to thirty articles (or book sections) dealing with the selected evolutionary concept or phylogeny of the chosen eukaryotic group will be collected by the student. S/he will have to read in detail about fifteen of the most relevant in order to write a critical review (see below). Several consultations will be held with the teacher to clarify difficult concepts, discuss the structure of the written work and monitor its good progress.
Mode of delivery (face to face, distance learning, hybrid learning)
Individual work and consultations with the teacher.
Recommended or required readings
List of research articles to be defined.
Written work / report
Additional information:
Writing a critical review of the phylogenetic literature of the chosen subject, the perspective of which is primarily historical (= evolution of the ideas over time, from antiquity to phylogenomics). The essay should have 10-15 pages of main text, 1 to 2 boxes on a colored background discussing more technical points and 4 à 8 original figures (ex. topologies). The main text must be understandable by a bachelor in biology and its structure should not include more than two levels of titles (unnumbered), as in a popularization review article. The work can be written in French or English and the final version must be sent to the teacher at least a week before the deliberations of the first or the second session.
Work placement(s)
Organisational remarks and main changes to the course
The course is scheduled in Q1, but it is possible to conduct the work in Q2 or during the summer months. In this case, the January grade is 0/20 and the course is only credited in the second session.
Contacts
Prof. Denis Baurain
Institut de Botanique B22 (P70)
denis.baurain@uliege.be
Mrs Rosa Gago
rgago@uliege.be