Species Concepts
Prezygotic Barriers
Postzygotic Barriers
Speciation
Evolution & Selection Review
100
The change in allele frequency in a population over time refers to what?
Microevolution!
100
True or False. Prezygotic barriers occur after fertilization, so the zygote isn't able to develop properly.
False! Prezygotic barriers prevent fertilization all together so the zygote wouldn't even be capable of being produced.
100
Post zygotic barriers are defined by what?
A barrier that occurs after the zygote is formed that prevents hybrids from surviving or reproducing
100
What are three possible outcomes when two newly formed species interact in a hybrid zone
Reinforcement: A wider separation between two species
Fusion: Two species join together as one
Stability: Hybrid offspring are as fit as the parent species, leading to sustained interbreeding and a maintenance of the hybrid zone.
100
True or False. Gene flow increases genetic variation among populations over time
False! If alleles spread then two different populations will slowly possess more similar allele frequencies.
200
True or False. Morphology is extremely objective and one of the best ways to differentiate species.
False! Morphology is subjective. There are plenty of species that look very similar despite being two completely different species.
200
Two species of flower are unable to pollinate each other due to blooming at different times in the year. This is an example of what prezygotic barrier?
Temporal Isolation
200
A farmer mates a goat and a sheep together. However, he finds he cannot use this hybrid animal to produce any new hybrids. This is an example of what postzygotic barrier?
Reduced hybrid fertility
200
Where reinforcement occurs, reproductive barriers
should be stronger for _______ than_______
species.
Sympatric than allopatric
200
Habitat fragmentation is an example of what evolutionary evidence?
Biogeography
300
What are the two requirements necessary for something to be considered a separate species under the biological species concept?
Must occur in nature as well as produce viable and fertile offspring!
300
Two species of flowers attract different pollinators!
300
A donkey and a horse procreate resulting in a mule. While the mule is fertile and able to reproduce, it's offspring are infertile. This is an example of what postzygotic barrier?
Hybrid Breakdown!
300
Ring species are a populations of species that show a genetic gradient based upon location. Can the intermediate species breed? What about those geographically further apart?
Intermediate species are capable of breeding with one another but those on the edge can not breed with those on the opposite end.
300
Give an example of natural selection in action.
1. Antibiotic resistance in bacteria
2.The diversification of finches on the Galapagos
400
What is one con or 'downside' to the phylogenetic species concept?
There is no standard for what counts as genetically different enough to be labeled as two different species.
400
A zoo wants to assist two related endangered species through artificial insemination. What type of prezygotic barrier can this NOT bypass?
Gametic! As even if the sperm and egg come together they are unable to form a zygote.
400
While goats and sheep are capable of interbreeding the zygote is incapable of developing properly and dies. This is an example of what?
Reduced hybrid viability
400
Sympatric speciation is driven by what factors? Name at least one.
1. Disruptive Selection: Selecting extremes of a phenotype rather than an intermediate
2. Habitat differentiation: They specialize in utilizing different habitats or resources in the shared environment
3. Polyploidy: The doubling of chromosomes can create new species that are genetically isolated (think of genetically engineered fruits)
400
The runaway selection hypothesis says what about how genes are selected in males?
When female preference evolved, males started leaning towards attractive traits and disregarding survival in order to prioritize passing down genes and finding a mate.
500
Both honeybees and bumblebees occupy an extremely similar niche. Despite that they are morphologically different and have genetic variance between the two species. Lastly, they are also incapable of breeding together. What species concept would label them as the same?
Ecological species concept!
500
One species of sea urchin is able to mate with another, but fertilization is rarely successful. What is this an example of what prezygotic barrier?
Gametic!
500
Why do postzygotic and prezygotic barriers exist?
In order to limit gene flow between diverging populations, which is crucial for the evolution of distinct species.
500
A single species of birds winds up separated on two different islands. After hundreds of generations we decide to test whether or not they can still breed. We discover that they can breed but when they do their offspring isn't viable and is sterile. How did this speciation occur?
Allopatric speciation!
500
A snake having leg bones which are buried in their muscle serve as an example of what kind of structure?
Vestigial structures!