Variations

• Biological species concept


  Idea that a species is a group of organisms that can potentially mate with another one of the group and produce viable, fertile offspring
• Hybrid


  Offspring between two different species that cannot reproduce but might be viable, like a mule
• Mechanisms of reproductive isolation


  Barriers that stop different species from producing healthy fertile offspring
• Prezygotic barrier


  Mechanism of reproductive isolation that prevents two species from ever mating to produce a zygote, like habitat isolation, temporal isolation, gametic isolation, etc...
• Habitat isolation


  Prezygotic barrier where two species prefer different environments and so will never cross paths
• Temporal isolation


  Prezygotic barrier where two species mate at different times of day or seasons and so will not mate with each other
• Behavioral isolation


  Prezygotic barrier where two species have different courtship behaviors or mate preferences so they don't find each other sexy
• Gametic isolation


  Prezygotic barrier where two species produce sperm and egg cells that can't combine, even if they do come across each other in mating
• Mechanical isolation


  Prezygotic barrier where the duckussy and the chickenis don't fit so their gametes can never meet
• Postzygotic barriers


  Mechanisms of reproductive isolation that ensure offspring of two different species doesn't ever reproduce, either through inviability or infertility
• Speciation


  When an ancestral species splits into two or more descendant species that are genetically different enough from each other that they can no longer interbreed
• Allopatric speciation


  Geographic separation of a species and subsequent evolution into distinct species
• Sympatric speciation


  When two species emerge from a parent species while they stay in the same geographic location
• Sympatric speciation can happen in plants when one with a different number of chromosomes pops up in a population because of a meiosis error, and then clones itself until it's a new species