Species and Speciation Flashcards
1
Q
What is a species?
A
- Interbreeding populations
- Subject to evolutionary forces
- Maintained by random mating within populations and gene flow
- Often have isolating mechanisms to prevent hybridisation
2
Q
What is the Biological Species Concept (BSC)?
A
Species are:
- Actually or potentially inbreeding natural populations
- Reproductively isolated from other groups
- Can hybridise
- Hybrids are not infertile or have low fitness
3
Q
Why are there issues with hybrids?
A
- Viable because inherited chromosomes are intact
- Sterile due to meiosis issues
- Sister chromosomes are different so don’t cross over
- Chromosomes are different sizes
- New gene combinations aren’t good because combinations of enzymes don’t work well together
4
Q
What are pros of the BSC?
A
- Makes sense
- Proven in some case
- Reveals cryptic species: species that are phenotypically similar but can’t interbreed
- Most widely used and accepted
5
Q
What are cons of the BSC?
A
- Species that form fertile hybrids don’t fit e.g. eucalypts
- Difficult to test in cases where it is difficult to breed in lab
- Cannot use fossil record
- Only applies to sexual organisms
6
Q
What is the Morphological Species Concept (MSC)?
A
- Relies on phenotypic similarity within species and differences between species
- Based on BSC ideas of gene exchange within groups leading to similarities and lack of exchange leading to divergence by drift or selection
7
Q
What are pros of the MSC?
A
- Doesn’t require testing of reproductive barriers
- Often easy to measure phenotypic characteristics
- Can use fossil and museum specimens
- Can deal with asexual organisms
8
Q
What are cons of the MSC?
A
- Difficult/slow to measure characteristics
- Phenotypic difference may be due to environment
- May miss cryptic species as they look the same
9
Q
What is the Phylogenetic Species Concept (PSC)?
A
- Tree inferred using representatives of a population
- Usually DNA sequence but also morphology
- Individuals sharing a common ancestor are a species
- DNA barcoding: sequence a mitochondrial gene in every type of organism to determine all known species
10
Q
What are pros of the PSC?
A
- Can deal with asexual organisms
- Soon whole genome will be sequenced cheaply
- Finds cryptic species
11
Q
What are cons of the PSC?
A
- Hard to know what percentage difference means different species
- Hybridisation can confound results
12
Q
How do species form?
A
Cladogenesis or anagenesis
13
Q
What is cladogenesis?
A
In a species one population is split off over time, stops breeding with the original population, and becomes its own species
14
Q
What is anagenesis?
A
One species changes slowly over time to become a different species
15
Q
What is speciation?
A
The process of a single species splitting into two reproductively isolate species (according to BSC)
