Chapter 14: Speciation and Macroevolution Flashcards
What is speciation?
The evolution of one or more new species from an ancestral species
What causes speciation and macroevolution?
Accumulation of microevolutionary changes over time
What are the mechanisms of isolation?
Geographic, reproductive, spatial and temporal
When do we know speciation has occurred?
When a single population becomes separate and cannot interbreed, this is called reproductive isolation
How does reproductive isolation limit breeding?
Different allele frequencies cause microevolutionary changes
How does reproductive isolation affect gene flow?
It stops it
What are the pre-reproductive isolating mechanisms?
Geological (separated by seas, mountains), temporal (time, breeding in different seasons or times of day), behavioural (different courtship patterns) and morphological (different reproduction structures)
What are the post-reproductive isolating mechanisms?
Gamete mortality (gametes do not survive), zygote mortality (zygotes do not survive) and hybrid sterility (adult offspring survive but are unable to reproduce)
What are the modes of speciation?
Allopatric, sympatric and parapatric
What is allopatric speciation?
Speciation that is due to physical or geographical isolation
What are geographical isolations?
Water, land, mountains, natural disasters, habitat fragmentation etc
What is habitat fragmentation?
A process in which habitats are lost resulting in the division of large habitat into smaller.
What causes habitat fragmentation?
Farming, mining, pollution, river floods
What does habitat fragmentation stop?
Gene flow
What is sympatric speciation?
Speciation occurs without physical or geographical isolation. it limits gene flow which can cause the evolution of a different species
What are sympatric isolation examples?
Feeding on different things, different mating patterns.
What does sympatric isolation require?
a reporductive barrier
What is parapatric speciation?
Occurs when species are separated by extreme change in habitat, they may still interbreed at border
How does parapatric speciation occur?
Species more to outer borders where they are better adapted (allele traits favoured). Gene flow will still continue on border creating a hybrid zone
What are the four patterns of evolution?
Divergent, convergent, parallel and co-evolution
What is divergent evolution?
The difference between groups of organisms lead to a critical point where they diverge to two separate species (can be caused by isolation). Page 266 Figure 14.4.1
What is convergent evoultion?
A process where unrelated organisms evolve similar adaptations caused by environmental pressures. Page 266 Figure 14.4.1
What is parallel evolution?
A process where unrelated organisms evolve similar adaptations in response to environmental factors. Page 266 Figure 14.4.1
What is co-evolution?
A process where an evolutionary change in one species influences an evolutionary change in the other. (e.g. predator and prey relationship)
What are the two factors which can cause and extinction?
Competition between species or environmental factors
How do environmental factors lead to extinction?
Species that cannot evolve to survive are replaced by ones that can
How does low genetic diversity affect species extinction?
Smaller gene pools are more prone as they are less resilient as they have less alleles. They are unable to evolve due to their limited alleles
What happens when a population with low genetic diversity is exposed to harsh environmental factors?
They are unable to evolve due to their low allele frequency and become extinct
