Species: Latin word meaning “kind”

Speciation: The origin of new species

Macroevolution: The evolutionary changes above the species level eg. The 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 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

author avatar
William Anderson (Schoolworkhelper Editorial Team)
William completed his Bachelor of Science and Master of Arts in 2013. He current serves as a lecturer, tutor and freelance writer. In his spare time, he enjoys reading, walking his dog and parasailing. Article last reviewed: 2022 | St. Rosemary Institution © 2010-2024 | Creative Commons 4.0

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