Define
Speciation
Process by which one species splits into two or more species. It is responsible for the tremendous biodiversity observable and links microevolution to macroevolution
Define
Macroevolution
Broad pattern of evolution above the species level
Define
Biological species concept
Species are differentiated by their ability to interbreed and produce fertile, viable offspring
Define
Morphological species concept
Species differentiated by body shape and features (subjective but works for asexual species)
Define
Ecological species concept
Species differentiated by how species interact with their environment
Define
Phylogenetic species concept
Species defined by the smallest group of individuals that share a common ancestor
Define
Reproductive isolation
Biological factors that prevents members of 2 different species from interbreeding and producing fertile + viable offspring
What are the prezygotic barriers?
- Habitat isolation
- Temporal isolation
- Behavioural isolation
- Mechanical isolation
- Gametic isolation
What are the postzygotic barriers?
- Reduced Hybrid Viability
- Reduced Hybrid Fertility
- Hybrid breakdown (above problems occur for hybrid-hybrid offspring)
Define
Allopatric speciation
Interruption of gene flow by geographical isolation. Groups are separated and gene pools may diverge, which leads to reproductive barriers
Define
Sympatric speciation
Interruption of gene flow despite lack of physical separation
What are some ways by which sympatric speciation occurs?
- Polyploidy (mutation-driven speciation)
- Habitat differentiation (subset of population exploits a habitat or diurnal/nocturnal cyclles)
- Non-random mating (ex: mosquitofish choosing mates with similar body shape)
What are the forms of polyploidy?
- Autopolyploidy: species just doubles its number of chromosomes, either autopollinate or mate with others 2ns
- Allopolyploidy: Infertile hybrid offspring that can propagate asexually (ex: 2n=6 and 2n=4) come together, create a 5 chromosome infertile offspring)
Define
Hybrid zone
Region in which members of different species meet and mate, producing some offspring of mixed ancestry (intermediate mediocre phenotype)
What are the possibilities for a hybrid zone (what can become of it)?
- Reinforcement: hybrids are less fit than parents, natural selections strengthens prezygotic barriers
- Fusion: reproductive barriers weaken/vanish, fusion of species
- Stability: continuous production of hybrids, happens in narrow hybrid zones
What are the ways in which species fall and rise?
- Plate Tectonics
- Mass Extinctions
- Adaptive Radiations
Define
Plate tectonics
- Continents float on mantle in a movement called continental drift
- Their collision causes the creation of mountains, islands (promotes geographical separation)
What were the biggest events of mass extinction?
Permian Extinction and Cretaceous Extinction
Describe
Permian Extinction
Permian Extinction: 250 mya for 500k years. Extreme volcanic activity, acid oceans, anoxia, global warming and formation of Pangea. Loss of 95% marine life and 70% terrestrial.
Describe
Cretaceous Extinction
Cretaceous Extinction: 65 mya, few k years. Asteroid collides with earth, volcanic activity, huge cloud of debris. Loss of dinosaurs and 50% marine life.
Describe
Adaptive radiations
- Rapid speciation and diversification
- Organisms will out vacant areas/niches otherwise occupied by other species
- Regional: face little competition after migrating to a new location
ex: Mammals adaptively radiated after Cretaceous Extinction
