Macroevolution: The evolutionary changes above the species level eg. Appearance of feathers during the evolution of birds from one set of dinosaurs
Anagenesis– one species over time becomes another species
Cladogenesis– one species, over time, splits and becomes two species
Morphogensis– look at fossils to figure out how species evolved
Biological species concept: Defines a species as a population or a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring with members of other populations
Reproductive isolation: the existence of biological factors that impede members of two species from mating
Prezygotic barriers: impede mating between species or hinder fertilization of ova if members of different species attempt to mate
Postzygotic barriers: often prevent the hybrid zygote from developing into a viable, fertile adult
Exploring reproductive Barriers:
Barriers that impede mating or hinder fertilization:
Habitat isolation: two species that occupy the same habitat may encounter each other rarely
Temporal isolation: species that breed during different times, seasons or years
Behavioral isolation: courtship rituals unique to certain species act as effective, reproductive barriers
Mechanical isolation: morphologic differences can prevent successful mating
Gametic isolation: sperm of one species may not be able to fertilize egg of another species
Barriers that prevent hybrid zygote from developing:
Reduced hybrid viability: genes of different parent species may interact and impair the hybrids development
Reduced hybrid fertility: hybrids are sterile
Hybrid breakdown: some first generation hybrids are fertile but when they mate with one another or a parent species, offspring of the next generation are sterile.
Other definition of species:
Morphological species concept: characterizes species by body shape, size and other structural features
Paleontological species concept: focuses on morphologically discrete species known only from the fossil record
Ecological species concept: views species in terms of their ecological niche
Phylogenic species concept: defines species as a set of organisms with a unique genetic history.
Allopatric speciation (geographical speciation): when a population gets split and new population evolve. This is due to:
RIMS – reproductively isolated
Sympatric speciation (instant speciation)
Auto polyploidy – cell undergoes mitosis, but sister chromosomes do not split (mitotic error), twice the number of chromosomes. Then meiosis occurs, and the gametes come together creating a tetraploid zygote.
Allopolyploidy – 2 cells undergo meiosis (meiotic error) = unreduced gametes. These two cells come together to form a hybrid. This undergoes meiosis. Another meiotic error occurs = unreduced gametes. These two gametes come together to for a new cell.
Adaptive radiation: the evolution of many diversely adapted species from a common ancestor upon introduction to various new environmental opportunities and challenges
Punctuated equilibrium: when new species appear suddenly, persist essentially unchanged and then disappear
Heterochrony: evolutionary change in the rate or timing of developmental events
Allometric growth: different growth rates for different parts of the body determine body proportions
Paedomorphosis: adults retain body structures that were juvenile in ancestral organisms
St. Rosemary Educational Institution. "Speciation: Prezygotic and Postzygotic Barriers." http://schoolworkhelper.net/. St. Rosemary Educational Institution, Last Update: 2016. Web. Retrieved on: Monday 27th June 2016. http://schoolworkhelper.net/speciation-prezygotic-and-postzygotic-barriers/.