unit 3

• Evolution refers to the gradual change in inherited traits within a population over successive generations
• Speciation specifically involves the formation of new and distinct species through various mechanisms within evolving populations
• Reproductive isolation is the inability of a species to breed successfully with related species due to various barriers
• Gene flow is reduced by reproductive isolation maintaining the integrity of species
• Prezygotic isolation barriers may refer to the mechanisms that inhibit individuals to copulate and have a successful fertilization event
• Temporal prezygotic barriers involves variation in the reproductive timing of individuals; individuals have different mating season
• Ecological prezygotic barriers are caused by the difference between the habitats of two incipient individuals
• Behavioral prezygotic barriers occurs when two species have different practices such as courtship patterns
• Mechanical prezygotic barriers are mainly dependent in the morphological features of the individuals for copulation or pollination
• Postzygotic isolation barriers refer to the mechanisms that inhibit offsprings to be complete because there will be problems with their fitness to survive and reproduce
• Hybrid inviability- the offspring of incipient individuals lack the capacity to achieve sexual maturation
• Hybrid infertility - hybrid offspring are sterile, therefore unable to reproduce
• Hybrid breakdown - the incipient individuals are capable to producing offspring up to the second generation only, minimizing the chance of continuity for the survival of these individuals
• Speciation rate is the time it takes for species to emerge
• Gradualism states that the changes that happen to species are usually small and the small changes accumulate through time.

  
• Punctuated equilibrium is a concept that states that the characteristics of species are relatively stable in optimum environmental conditions; however, environmental changes may appear and destabilize the traits
• Allopatric speciation can be referred to as the process of two populations becoming geographically isolated from each other
• Peripatric speciation is the process by which a population splits into two or more species. as a result of the combined effect of genetic drift and geographic isolation
• Parapatric speciation does not involve specific barrier to inhibit gene flow. The populations live in the same habitat but due to some random event, the populations do not mate randomly
• Sympatric speciation is when a population splits into two separate species though there is no geographic distance because they tend to develop different niches
• speciation between the island and mainland populations

  Peripatric
• speciation of populations separated by the Amazon river

  allopatric
• speciation of fungi populations in different parts of the same plant individual

  sympatric
• speciation of plant populations in contaminated and non-contaminated soil

  Parapatric