what is meant by secondary contact?
- Secondary contact is a way to prevent 2 different species from interbreeding
What is reinforcement?
- Reinforcement increases the reproductive isolation between populations through the selection against hybrid offspring. Hybrid offspring have low fitness and natural selection results in assertive mating and prezygotic isolation
What is pre-zygotic reproductive isolation and post-zygotic reporductve isolation? What are examples of each?
- Prezygotic isolation is the divergence of traits between populations that prevent fertilization from occurring (indicates lots of genetic differences). Examples are different breeding seasons, different reproductive organs, different mating rituals. Post-zygotic isolation means the hybrid offspring are sterile or infertile. Examples are mules and drosophila flies.
what is isolation by distance?
- Isolation by distance is when populations that live nearby are genetically more similar to each other than populations that live farther apart. These populations can interbreed, but often times traits brought in from the other population will not be passed down and kept in the population because they are not conducive to survival in the environment.
When does hybridization result in either reinforcement or speciation?
- Hybridization results in reinforcement when a hybrid has low fitness or is sterile. Speciation of a hybrid occurs if the hybrid has a high fitness and is able to reproduce amongst themselves.
what is allopatric speciation?
Allopatric speciation is the divergence of a new species when there is geographic isolation. This will occur if 2 different species are facing different environmental factors. As natural selection acts on the population, it favors different adaptations. An example of this divide is the Isthmus of Panama causing the Pacific and Atlantic oceans to be isolated. This caused many shrimp species in the ocean to diverge and when they were placed together again they did not interbreed.
what is sympatric speciation?
- Sympatric speciation is when populations diverge without any geographic isolation. An example is the rhagoletis flies. In the northern united states there are 2 genetically distinct groups of these flies. One group lives on hawthorne trees and the other lives in apple trees.
phylogenetic species concept
Phylogenetic species concept identifies species as being monophyletic based on comparisons with other populations. This approach looks at genetic divergences as well as morphological traits. This approach works on sexually and asexually reproducing plants, fossils and in many cases prokaryotes. Species identification is based on statistically significant differences of traits.Phylogenetic concept is useful for systematisms because it focuses on the phylogenetic history of organisms
biological species concept
Biological species concept is when species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups. This is when populations do not hybridize regularly in nature, or when they fail to produce fertile offspring. This does not work for fossils because you cannot interbreed them. Also, it does not work on asexually reproducing species
morphospecies concept
Morphospecies concept is when species designation and identification is based on the morphological differences between populations. This is the primary way fossils are assigned to species. This approach works very badly for some fungi, bacteria and archaea.
What is horizontal gene transfer and in what organism do you see it?
- Horizontal gene transfer is when organisms within the same generation trade genetic material. This is mostly seen in bacteria.
what are cryptic species?
- A cryptic species is a group of organisms that are genetically distinct and do not interbreed, but are morphologically almost indistinguishable. Examples include butterflies and wasps.
