What is a species?The most accepted definition of a species is derived from the biological species concept:Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groupsEarth’s organisms are so varied that this definition does not apply to all of them: only to organisms that multiply through sexual reproduction.The definition of species does not apply to bacteria and archaea, which reproduce through simple cell divisionMorphologial Species conceptFocus on aspects of organisms other than reproductive isolation as defining featuresCharacterizes species based on physical features such as body size and shapeCan be used effectively to classify asexual speciesCommon Descent with modificationWithin the theory of evolution, a key principle is that of common descent with modification.This principle describes the process by which species of living things can undergo modification over time, with such change sometimes resulting in the formation of new, separate species.Speciation can result from the mechanisms of biological evolutionSpeciation (macroevolution)Process by which a population of organisms develops traits that make it into a new type of organismProcess requires reproductive isolation so random mutations are not sharedProcess results in two populations that can no longer breed successfullyEx. Horses and donkeys have infertile youngOther mechanisms of SpeciationHybridization – rare fertile hybrid offspringPolyploidy – more than two sets of DNABoth happen more often in plants than in animalsThere is a rat in South America with 4 sets of DNA in each cell.Polyploidy in green tree frogs2 groups of frogs, identical in appearance, but their calls are different.Overlapping ranges in eastern U.S.One species has 24 chromosomes in each cell, the other has 48 chromosomes in each cell.More common in amphibians than other animals.Systematics and PhylogenySystematics names and arranges species in a manner that indicated:the common ancestors they share and the points at which they diverged from each otherPhylogenyevolutionary history, of organismsNodesThe common ancestor points at which species divergeConvergent EvolutionAnalogous traits are characteristics (such as bat wings and insect wings) that are the same because they were produced by convergent evolution and not because they descended from a common structure in an ancestor they shared.Analogous traits:Features that are produced by convergent evolutionHomologous traits:Features that are inherited from a common ancestorHow do you know whether traits are homologous or analogous?DNA AnalysisBIO 101 1nd Edition Lecture15 Outline of Last Lecture II. Biological EvolutionIII. Natural SelectionIV. Change In populationsV. ControversyVI. Darwin’s influencesVII. MacroevolutionOutline of Current Lecture VIII. What is a species?IX. Species conceptX. Common Descent with modificationXI. SpeciationXII. PolyploidyXIII. Convergent evolution Current Lecture What is a species?- The most accepted definition of a species is derived from the biological species concept:o Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups- Earth’s organisms are so varied that this definition does not apply to all of them: onlyto organisms that multiply through sexual reproduction.- The definition of species does not apply to bacteria and archaea, which reproduce through simple cell division Morphologial Species concept- Focus on aspects of organisms other than reproductive isolation as defining featuresThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Characterizes species based on physical features such as body size and shape- Can be used effectively to classify asexual speciesCommon Descent with modification- Within the theory of evolution, a key principle is that of common descent with modification. - This principle describes the process by which species of living things can undergo modification over time, with such change sometimes resulting in the formation of new, separate species.  Speciation can result from the mechanisms of biological evolution- Speciation (macroevolution)o Process by which a population of organisms develops traits that make it into anew type of organismo Process requires reproductive isolation so random mutations are not sharedo Process results in two populations that can no longer breed successfully Ex. Horses and donkeys have infertile young Other mechanisms of Speciation- Hybridization – rare fertile hybrid offspring- Polyploidy – more than two sets of DNAo Both happen more often in plants than in animalso There is a rat in South America with 4 sets of DNA in each cell. Polyploidy in green tree frogs- 2 groups of frogs, identical in appearance, but their calls are different.- Overlapping ranges in eastern U.S.- One species has 24 chromosomes in each cell, the other has 48 chromosomes in each cell.- More common in amphibians than other animals.Systematics and Phylogeny - Systematics names and arranges species in a manner that indicated:o the common ancestors they share and the points at which they diverged fromeach other- Phylogenyo evolutionary history, of organisms- Nodes o The common ancestor points at which species diverge Convergent Evolution- Analogous traits are characteristics (such as bat wings and insect wings) that are the same because they were produced by convergent evolution and not because they descended from a common structure in an ancestor they shared. - Analogous traits:o Features that are produced by convergent evolution- Homologous traits:o Features that are inherited from a common ancestor o How do you know whether traits are homologous or analogous?  DNA