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Diversitatea biologica si Clasificare | Nomenclatura | Constructia arborilor filogenetici
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Diversitate biologica si clasificare
Taxonomia este acea ramura a biologiei care se ocupa cu identificarea si denumirea organismelor. Se pare ca vechiul filosof grec Aristotel a inceput discutia asupra taxonomiei. Naturalistului britanic John Ray i se atribuie revizuirea conceptului de numire si descriere a organismelor. In anii 1700, botanistul suedez Carolus Linneus a clasificat toate organismele cunoscute atunci in doua mari grupuri: regatele Plantae si Animalia. Robert Whittaker a propus in 1969 cinci regate: Plantae, Animalia, Fungi, Protista si Monera. Alte scheme care implica un numar si mai mare de regate au fost propuse in ultima vreme, insa majoritatea biologilor angajeaza cele cinci regate ale lui Whittaker. Studii recente sugereaza utilizarea a trei domenii: Archaea, Bacteria si Eukarya. Clasificarea unui trandafir este prezentata in Figura 1,
Figura 1. gta 5 porno Taxonomia unei specii de plante selectate. Retineti incluzivitatea crescanda a rangurilor taxonomice „superioare”. Regatele au mult mai multe tipuri de creaturi in ele decat speciile. Imagine din Purves si colab., Life: The Science of Biology , editia a IV-a, de Sinauer Associates (www.sinauer.com) si WH Freeman (www.whfreeman. porno chineze com), folosita cu permisiunea.
Figura 2. Clasificarea unei singure specii de animale. Retineti compozitia similara a cunoasterii animale de mai sus in comparatie cu regnul plantelor. Imagine din Purves si colab., Life: The Science of Biology , editia a IV-a, de Sinauer Associates (www.sinauer.com) si WH Freeman (www. filme porno dur whfreeman.com), folosita cu permisiunea.
Linneus a incercat sa descopere (sau sa clasifice) toate speciile cunoscute din timpul sau (1753). Clasificarea ierarhica lineana s-a bazat pe premisa ca specia era cea mai mica unitate si ca fiecare specie (sau taxon) a cuibarit intr-o categorie superioara.
Linneus a dezvoltat, de asemenea, conceptul de nomenclatura binomiala, prin care oamenii de stiinta care vorbesc si scriu diferite limbi pot comunica clar. De exemplu, Man in engleza este Hombre in spaniola, Herr in germana, Ren in chineza si Homo in latina. Linneus s-a stabilit pe latina, care era limba oamenilor invatati la acea vreme. Daca un om de stiinta se refera astazi la Homo , toti oamenii de stiinta stiu ce organism / taxon inseamna el sau ea. porno cu grasi
Construirea arborilor filogenetici Inapoi sus
Taxonomia face parte dintr-o diviziune mai mare a biologiei cunoscuta sub numele de sistematica. Determinarea filogeniei este un obiectiv al sistematicii. Acest lucru se realizeaza prin construirea arborilor filogenetici, care intr-un sens reprezinta ipoteze evolutive si incearca sa defineasca grupuri monofiletice. Pentru a construi acesti copaci, trebuie sa avem date, care provin din caracteristicile utilizate in clasificare. Exista mai multe metode de clasificare: traditionala, autentica si cladista. Ele difera prin modul in care apreciaza anumite personaje. Sa luam in considerare modul in care clasificarea traditionala trateaza reptilele, pasarile si mamiferele, asa cum se arata in Figura 3.
Figura 3. filme porno cu blonde si negri Clasificarea traditionala a reptilelor, pasarilor si mamiferelor. Imagine din Purves si colab., Life: The Science of Biology , editia a IV-a, de Sinauer Associates (www.sinauer.com) si WH Freeman (www.whfreeman.com), folosita cu permisiunea.
Clasificare traditionala
Datele utilizate in sistematica traditionala subliniaza atat ascendenta comuna (monofilie), cat si cantitatea de divergenta intre grupuri. film porno cu pule mari Traditional, datand de Linneaus, este ca pasarile au pene, reptilele au solzi, iar mamiferele au par. Folosind acest lucru ca personaj major, a fost construita o clasificare ca cea de mai sus. Fosilele, dovezi ale vietii trecute, nu sunt incluse in aceasta clasificare. Deoarece toate aceste grupuri au oul amniotic sau o modificare a acestuia, acestea ar fi unite intr-un taxon mai mare. Linneus a plasat fiecare dintre aceste grupuri intr-o clasa separata in cadrul Phylum Chordata. Un caracter primitiv este unul prezent in stramosul comun si in toti membrii grupului, cum ar fi oul amniotic. Un caracter derivat este unul care se gaseste numai intr-o anumita linie din cadrul grupului mai mare. In exemplul nostru de mai sus, parul si penele pot fi privite ca personaje derivate. porno cu sloboz O viziune traditionala a grupului nostru de exemplu este ca pasarile si mamiferele au evoluat din reptile datorita caracterelor lor derivate unice.
Cladistics and Cladograms
Cladistics is a type of systematics developed by
the late German biologist Willi Hennig, who attempted to formulate a
more objective method of classifying organisms. Cladists group
organisms based on the presence of shared derived characters, not the
overall similarity of potential group members.
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In the example cited
in Figure 3, the amniotic egg would be used to unite a group sharing
common ancestry, since it would NOT be present in a group that was
not in the lineage. The use of feathers and hair to separate birds
and mammals from reptiles would NOT factor into a cladistic
hypothesis, or cladogram, since these are characters unique to only
one taxon in our group. Such an approach is shown in Figure 4.
The value of cladistics lies in its capacity to generate (and provide a set of criteria for the evaluation) of multiple hypotheses (alternate cladograms) that can be evaluated with additional data. Almost always the “correct” cladogram employs the principle of parsimony, which proposes that the shortest number of steps or character state changes is most likely correct. filme porno facute in romania An important question….is evolution always parsimonmious? However the ultimate answer to that question unfolds, the rigor cladistics introduces to systematics is useful in getting traditional systematists to look at their subjective classifications in a new light. On the diagram shown in Figure 5, shared derived characters are indicated as hauchers across the lines. The mammal clade (in this case represented by mouse and chimpanzee) is united by fur, the lizard, pigeon, mouse-chimp clade is united by claws or nails, etc.
Figure 4. iulia vantur porno Dissected cladogram of repriles, birds, and mammals. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.
Figure 5. porno cu ruby Cladogram of the vertebrate chordates. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.
Cladistic Classification
The example used above, if treated cladistically, would produce a very different classification! Note that crocodiles have more in common (in a cladistic sense) with birds than they do with other reptiles. animati porno Birds and crocs form a clade, or monophyletic group united by shared derived characters not present in the other groups. If we construct a Linnean group from this cladogram, we have a class of birds and crocodiles, a second class of lizards, snakes, and turtles, and a third class of mammals, as shown in Figure 6.
Figure 6. Cladistic-based classification of reptiles, birds, and mammals. Note the changes betweeen the cladistic and traditional classifications as shown in Figure 3. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer. site uri de filme porno com) and WH Freeman (www.whfreeman.com), used with permission.
One of the more interesting applications of cladistics is to the question of the pandas. The giant panda was once thought to be a bear, but later its racoon-like characters caused it to be placed closer to racoons. The red (lesser) panda lives in the same areas of China as the giant panda, but has a far greater similarity with racoons, as shown in Figure 7. DNA hybridization studies suggest the giant panda is in the bear clade, while the red panda is in the racoon clade. Both share a common ancestry, as indicated by shared derived characters, followed by convergent evolution of other characters. porno masaje The diagram above indicates this divergence from common ancestry, and even attempts to show the time of that divergence.
Figure 7. Cladistic analysis of the relationships of the giant and lesser pands. Note: time has been added onthe horizontal scale after the cladistic analysis was done. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www. porno 18+ whfreeman.com), used with permission.
Phenetics
Phenetics is a process by which taxa are clustered
together based on the number of their similarities (or differences,
depending on the numerical coefficient employed). Traits are measured
and either converted into integers or input directly as numerical
data. Theses data are then mathematically processed using an
algorithm that generates a similarity (or distance as the case may
be) matrix. Various graphical representations of this matrix include
a phenogram, and principal coordinate plot.
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Phenetic classifications
are plagued by problems of convergence and parallelism, but are
useful in their attempt to objectify the classification process. My
previous work on triprojectate pollen employed phenetics to deal with
a wide array of subjective ratios or other classification methods. femei bune porno
Convergence was a given with this group of fossil pollen produced by
one or more groups of unknown extinct plants. Since monophylesis
could not be established for the entire group, phenetics was use to
help delineate possible monophyletic groups for eventual cladistic
study.
Nomenclature | Back to Top
The naming of species and other taxa follows a set of rules, the International Code of Botanical Nomenclature (ICBN, click here for an online version) for plants, the International Code of Zoological Nomenclature (ICZN) for animals.
Some general rules for nomenclature:
- All taxa must belong to a higher taxonomic group. Often a newly discovered organism is the sole species in a single genus, within a single family…etc. filme porno cu vedete romane
- The first name to be validly and effectively published has priority. This rule has caused numerous name changes, especially with fossil organisms: Brontosaurus is invalid, and the correct name for the big sauropod dinosaur is Apatosaurus, Eohippus (the tiny “dawn horse”) is invalid and should be referred to as Hyracotherium. Sometime, however, names can be conserved if a group of systematists agrees.
- All taxa must have an author. When you see a scientific name such as Homo sapiens L, the L stands for Linneus, who first described and named that organism. Most scientists must have their names spelled out, for example Libopollis jarzenii Farabee et al. (an interesting fossil pollen type I stumbled across a very long time ago!).
The Kingdoms of Life | Back to Top
Linnaeus originally placed all living things into either the plant or animal kingdoms. aunt porno As scientists learned more about the biology of many organisms, this constraining into two kingdoms became less and less defensible.
Evolutionary theory and the cell theory provide us with a basis for the interrelation of all living things. We also utilize Linneus’ hierarchical classification system, adopting (generally) five kingdoms of living organisms. Viruses, as discussed later, are not considered living. Recent studies suggest that there might be a sixth Kingdom, the Archaea.
Figure 8. A simple phylogenetic representation of three domains of life” Archaea, Bacteria (Eubacteria), and Eukaryota (all eukaryotic groups: Protista, Plantae, Fungi, and Animalia). Image from Purves et al. porno virtual , Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.
Monera
Monera are the only kingdom composed of prokaryotic organisms, they have a cell wall, and lack both membrane-bound organelles and multicellular forms. The Archaebacteria, the most ancient of this kingdom, are so different that they may belong to a separate kingdom. Other groups of Monera include the cyanobacteria (autotrophic) and eubacteria (heterotrophic). anne hathaway porno
Protista
The most ancient eukaryotic kingdom, protists include a variety of eukaryotic body (single-celled-colonial-multicellular?) and nutritional heterotrophic, autotrophic, and both) forms. Perhaps they are best defined as eukaryotes that are NOT fungi, animals, or plants.
Fungi
Fungi are a eukaryotic, heterotrophic, usually multicellular group having multinucleated cells enclosed in cells with cell walls. They obtain their energy by decomposing dead and dying organisms and absorbing their nutrients from those organisms. Some fungi also cause disease (yeast infections, rusts, and smuts), while others are useful in baking, brewing, as foods, drugs and sources for antibiotics.
Plantae
Plants are immobile, multicellular eukaryotes that produce their food by photosynthesis and have cells encased in cellulose cell walls. Plants are important sources of oxygen, food, and clothing/construction materials, as well as pigments, spices, dyes, and drugs.
Animalia
Animals are multicellular, heterotrophic eukaryotes that are capable of mobility at some stage during their lives, and that have cells lacking cell walls. porno maicute Animals provide food, clothing, fats, scents, companionship, and labor.
Links | Back to Top
- World Species List: Animals, Plants, and Microbes An exhaustive list of species.
- Diversity of Life Index A long-loading page, but well worth the wait. A collection of websites focusing on the diversity of life.
- Taxonomy of Life A listing of taxa, but not much beyond that.
- International Code of Botanical Nomenclature (Tokyo) The nomenclature rules for plants, algae, and fungi.
- Phylogeny Exercise (U Tennessee-Martin) Excellent site that privides a great deal of clear and easy to use information.
- Phylogeny & Reconstructing Phylogenetic Trees (David E. Joyce, Clark University) A Java-enhanced site that details the problems of reconstructing phylogenetic trees.
- The Phylogeny of Life and Journey into Phylogenetic Systematics (UCMP, Berkeley) Both explain the relationships and theory behind such evolutionary hypotheses. The latter gives a brief introduction into cladistics.
- The International Willi Hennig Society A society for cladists, with links to other sites as well as software.
- Biodiversity and Biological Collections Webserver
- Principles of Plant Taxonomy (James L. Reveal, U Maryland) Outline of the basic concepts.
- Taxonomic Hierarchy of Animals (The Zoological Record) Nested list of taxa in the Animal Kingdom.
- Linnean Herbarium, (English Version) Swedish Museum of Natural History
Text © 1998, 2000, 2001, 2002, de MJ Farabee, toate drepturile rezervate. Este incurajata utilizarea in scopuri educationale.
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