6 - Classification PDF

6 - Classification Notes Status Done Lab Notes Status / TAXONOMIC CLASSIFICATION 🦋 → Formal arrangement of things (animal, plants, rocks..) and any of its element is a TAXON (pl. TAXA)...

6 - Classification Notes Status Done Lab Notes Status / TAXONOMIC CLASSIFICATION 🦋 → Formal arrangement of things (animal, plants, rocks..) and any of its element is a TAXON (pl. TAXA) Carolus Linnaeus created a classification system that is still in use today → scientific name Hierarchical classification Binomial nomenclature - ex Tiger is Panthera (genus) Tigris (species) Species: basic unit in taxonomy, such as the stage/age in stratigraphy BIOSPECIES: array of population which are actually or potentially interbreeding and reproductively isolated under natural conditions, with morphologic features in common → fertile offsprings - BUT how to recognize/define biospecies when dealing with past organisms having no modern representatives? → MORPHOSPECIES Fossils are challenging, especially rare species - complications for paleontologists CHRONOSPECIES → species that are arbitrarily defined as steps of the evolutive process Intraspecific variability → morphological variability within given species (size, male/female, environment) → let’s clear some things up 1. Morphospecies Definition: A morphospecies is a group of organisms that are classified together based on their physical characteristics (morphology), such as size, shape, color, or structure, rather than on genetic relationships or reproductive isolation. 6 - Classification 1  Key points: Morphospecies are identified by observable traits. This concept is often used when studying fossil species, where genetic information isn't available. It’s a more practical, but sometimes less precise, method because individuals with similar morphologies might not be closely related genetically, and conversely, closely related organisms might not look alike due to convergent evolution or other factors. Example: You might have two species of birds that look very similar in terms of beak shape and feather coloration, so they would be classified as separate morphospecies, even if they could potentially interbreed. 2. Biospecies (Biological Species) Definition: The biospecies concept is based on reproductive isolation — a species is defined as a group of organisms that can interbreed in nature and produce fertile offspring, and are reproductively isolated from other such groups. This concept was famously proposed by Ernst Mayr in the 20th century. Key points: Biospecies are reproductively isolated from other groups; they don’t naturally interbreed or, if they do, their offspring are sterile (e.g., mules, which are hybrids between donkeys and horses). This concept is primarily focused on the ability of individuals to exchange genetic material. It’s a very effective concept for sexually reproducing species but doesn’t work as well for asexual species or species that can hybridize in certain conditions (like hybrid zones). Example: A population of frogs that can interbreed and produce fertile offspring with each other, but not with frogs from a different population, would be considered a biospecies. 3. Chronospecies Definition: Chronospecies refers to a species or group of organisms that exists at different points in time, typically through evolutionary change. 6 - Classification 2  These are often used in paleontology or evolutionary biology to describe species that evolved over long periods of time, where a single lineage gradually changes into another due to accumulation of mutations and adaptations. Key points: Chronospecies are viewed as a sequence of species that evolve from one another over time. They are not defined by current reproductive isolation or morphology but by their place in an evolutionary timeline. This concept is especially useful when studying fossil species or long- term evolutionary trends, as the organisms in the lineage may no longer be genetically compatible or similar in morphology but are linked through their evolutionary history. Example: A population of trilobites that evolves into different forms over millions of years can be classified as different chronospecies, even though they might belong to the same ancestral lineage. Criteria for Species Concept Focus Typical Use Cases Classification Physical Similar morphology Fossils, cases with Morphospecies appearance (shape, size, color, etc.) limited genetic data Reproductive Ability to interbreed and Modern sexually Biospecies isolation produce fertile offspring reproducing species Evolution over Gradual evolutionary Paleontology, Chronospecies time change through time evolutionary studies 6 - Classification 3