bio 140 - module 5

• species - a group of organisms that share characteristics
• Traditionally, species have been defined based on?

  • phenotypic characteristics
• In this, a species is a group of interbreeding, or potentially interbreeding, organisms that is reproductively isolated from other species?

  • evolutionary genetics
• anagenesis - one species is transformed over time into another species and at all times, only one species exists.
• cladogenesis - one species splits into two or more species.
• phyletic evolution - aka anageneis
• Branching evolution - aka cladogenesis
• Anagenesis is the transformation of an unbranched lineage of organisms to a state different enough from the ancestral population which justifies naming it a new species.
• anagenesis - “evolution within species”
• cladogenesis - the budding of one or more species from a parent species that continues to exist
• Morphospecies - Species defined by their anatomical features and is Used by Linneaus
• Morphospecies - Still the most common method used today
• Two populations morphologically similar are almost indistinguishable
• In morphospecies concept, It is difficult to determine if a set of organisms represents multiple species or a single species with extensive phenotypic variation
• biological species concept - population or groups of populations whose members interbreed with one another successfully and produce viable, fertile offspring that is capable of genetic exchange
• Biological species conept can not interbreed with members of other species
• BSC not applicable to asexually reproducing species.
• BSC can not be applied to extinct organisms represented only by fossils
• EVOLUTIONARY SPECIES - is a single lineage (an ancestor-descendant sequence) of populations or organisms that maintains an identity separate from other
• PHYLOGENETIC SPECIES - is an irreducible (basal) cluster of organisms that is diagnosably distinct from other such as clusters, and within which there is a parental pattern of ancestry and descent
• Phylogenetic species - The smallest monophyletic group of common ancestry
• GENEALOGICAL SPECIES - Species are “exclusive” groups of organisms, where an exclusive group is one whose members are all more closely related to one another than to any organism outside the group
• PSC and BSC - Most advocated
• phylogenetic species concept - Emphasizes species as outcome of evolution that is the product of history of evolutionary divergence
• biological species concept - : Emphasizes the process by which species arise and takes a prospective view of the future status of populations
• sibling species - reproductively isolated species that are difficult to distinguish by morphological characteristics
• sister species - species considered to be each other’s closest relatives, derived from an immediate common ancestor based on phylogenetic analysis
• chronospecies - phenotypically distinguishable forms in an ancestral-descendant series in the fossil record that are given different names
• subspecies - populations of a species that are recognizably distinct and occupy different geographic areas
• geographic races - subspecies in zoology
• ecotypes - subspecies in botany
• semispecies - genetically differentiated parapatric populations that are thought to be partially (or not fully) reproductively isolated; they are nearly, but quite, different species
• reproductive barriers - any factor/s that impede two species from producing fertile hybrids
• reproductive barriers contributes to reproductive isolation
• Prezygotic - before the zygote is formed
• Postzygotic - after fertilization
• Prezygotic - features that impede transfer of gametes to members of other species
• Premating -potential mates do not meet or potential mates meet but do not mate
• postmating - mating or gamete transfer occurs but zygotes are not formed
• Postzygotic - Hybrid zygotes are formed but reduced fitness