Speciation Flashcards
Define Speciation
The split of a species into 2 or more species
What is the most generally accepted species concept? What does it describe?
The Biological Species Concept (BSC) describes that groups that actually or potentially inbreed and produce fertile offspring in nature, and which cannot form fertile offspring with other groups is considered a species.
Name the three species concepts you are responsible for on the midterm and their definitions.
- Biological Species Concept (populations that mate within themselves)
- Morphological species (groups with similar features)
- Ecological (groups with similar niches in their environment)
Identify the two types of reproductive barrier
Prezygotic/Postzygotic
What are the two categories of prezygotic barriers to reproduction? Name the 5 sub categories.
Prezygotic barriers that occur before mating include habitat isolation, temporal isolation, and behavior/pollinator isolation
Prezygotic barriers that occur after mating include mechanical isolation and gametic isolation.
What is the difference between mechanical isolation and gametic isolation in prezygotic reproductive barriers?
Mechanical isolation occurs when a physical barrier prevents mating between two species, and gametic isolation is when sperm and eggs come into contact, but no fertilization can happen.
Does birth occur in prezygotic or postzygotic reproductive barriers?
postzygotic
What are the two types of postzygotic reproductive barrier? Explain them.
Genetic incompatibilities lead to an offspring with reduced survival chances or reproductive ability.
Ecologically-dependent postzygotic barriers occur when the offspring has phenotypes that are not matched to their environment.
Define allopatric populations.
Populations that occur in different areas that do not overlap.
What is the opposite of an allopatric population?
A sympatric population occurs in the same area.
What do we call two partially overlapping populations?
Parapatric populations.
What evolutionary variable must change within the population for sympatric speciation to occur?
The gene flow between two groups must decrease or stop completely.
What are the three mechanisms of speciation?
Ecological, polyploidization, and reinforcement
What drives ecological speciation?
Unique environmental characteristics select species to diverge in two different pathways to fill two different niches. This is also called divergent natural selection.
Where is polyploidization found most often? What is it?
Polyploidization is most commonly found in ferns and flowering plants. It is the increase in number of sets of chromosomes.
What is the difference between an autopolyploid and an allopolyploid?
Autopolyploids have two or more individual sets of chromosomes from the same species. Allopolyploids have two or more chromosome sets from different species.
How can we describe hybrid crosses between two species when reinforcement speciation is present?
We can say hybrid crosses are less fit as the strengthening of the prezygotic barrier is selected in response to decreased fitness of the hybrid cross.
In which mechanism of speciation is allopatry present? What about sympatry?
In ecological speciation, any geographical context can be present. Polyploidization occurs in sympatric context, and reinforcement is also expected to be more prevalent in more sympatric contexts.
What is a downside of using BSC to describe speciation?
The Biological Species Concept cannot describe asexual taxa, fossils, and some animal species have gene flow within different species but still maintain divergence.
What is a cryptic species and why is it important?
Cryptic species are identical in appearance, but do not interbreed within populations. This is important to consider when taking the morphological species concept into account.
How would one experimentally study speciation?
With multiple populations of a common ancestor are exposed to separate environmental conditions.
How would one test for ecologically-dependent postzygotic isolation of hybrids?
Reciprocal transplants of parents and hybrids into different environments can be done in both habitats.
