Species: Latin word meaning “kind”

Speciation: The origin of new speciesSpeciation Speciation: Prezygotic and Postzygotic Barriers

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:

  • Geographic isolation
  • Genetic divergence
  • 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



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