speciation Flashcards
microevolution
evolutionary changes that occur at the species level
species
A species is one or more populations of individuals that can interbreeding under natural
conditions and producing fertile offspring, and are reproductively isolated from other such populations
speciation
the formation of a new species from existing species
macroevolution
Forming of new species
prezygotic isolating mechanism
These are mechanisms which either prevent mating or prevent fertilisation of eggs if individuals from different species attempt to mate
behavioural (prevention of mating)
behaviours that prevent other spp. from recognizing or selecting them for mating
temporal (prevention of mating)
Two species that live in the same habitat or the same niche but have different mating seasons due to varying reproductive cycles
Ecological (prevention of mating)
two species that live in same general area but in different habitats
Mechanical (prevention of fertilization)
structural differences in reproductive organs that prevent fertilisation.
Gametic isolation (prevention of fertilization)
If egg and sperm from 2 different species do happen to meet gametic isolation will ensure that zygote doesn’t form
Post-zygotic isolating mechanisms
that prevent hybrid zygotes from developing into a healthy and fertile
adult
Hybrid inviability (EXAMPLES)
Development of hybrid zygote stops in early development and it dies before birth; hybrid embryos of sheep and goat often die
Hybrid sterility (EXAMPLES)
Hybrid produced is sterile (cannot produce normal gametes); horse and donkey can create a mule but mule cannot reproduce
Hybrid breakdown (EXAMPLES)
Hybrid forms but when these hybrids mate their offspring are weak and sterile; many cotton plant species can produce fertile hybrids but then their offspring die as seeds or in early development
sympatric speciation
occurs when populations that live in the same habitat diverge genetically and become reproductively isolated.
allopatric speciation
occurs when populations are separated by a geographical barrier and diverge genetically
divergent evolution
a pattern of evolution in which species that were once similar to an ancestral species diverge, or become increasingly distinct. In other words, as populations adapt, they become less and less alike
convergent evolution
When 2 or more species become increasingly similar in phenotypes due to experiencing similar selective pressures (similar environments)
gradualism
views evolutionary change as slow and steady, before and after a divergence
punctuated equilibrium
views evolutionary history as long periods of stasis, or equilibrium, that
are interrupted by periods of divergence
how humans impact evolution
- conversion of wilderness into cropland
- development of areas for tourism
- building urban subdivisions and roads
outcome of how humans impact evolution
- speciation through adaptive radiation after geographical isolation
- speciation through genetic drift after a bottleneck effect
- species endangerment and/or extinction due to insufficient genetic diversity from population isolation (this is the case for the giant panda)