Speciation Flashcards
What is speciation?
The origin of new species; the key point where microevolution and macroevolution intersect.
How many species have been described?
2-3 million species are known to science.
How many species are estimated to exist?
5-100 million
What does it mean for members of a biological species to be reproductively compatible?
They cannot interbreed with other populations.
What is the critical issue of reproductive isolation?
The reduction of gene flow between populations so that populations can diverge in allele frequencies (by genetic drift or by natural selection) and become reproductively isolated.
What is reproductive isolation?
The existence of biological factors (barriers) that impede two species from producing viable, fertile hybrids.
What does the biological species concept define species as?
Species are groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups.
How does temporal or habitat isolation work?
Potential mates do not meet, thus causing reproductive isolation.
How does ethological, behavioral, or sexual isolation work?
Potential mates meet but do not mate.
How does mechanical isolation work?
Copulation occurs, but there is no gamete transfer.
How does incompatibility work?
Gametes are transferred, but there is no fertilization.
How does hybrid inviability work?
Fertilization occurs, but F1 hybrid has reduced viability.
How does hybrid sterility work?
The F1 hybrid is viable but has reduced fertility.
How does hybrid breakdown work?
There is reduced viability/fertility in F2 or backcross hybrids.
Which barriers are premating?
- Temporal or habitat isolation
- Ethological, behavioral, or sexual isolation
Which five barriers are postmating?
- Mechanical isolation
- Incompatibility
- Hybrid inviability
- Hybrid sterility
- Hybrid breakdown
Which barriers are prezygotic (prevents zygotes from forming)?
- Temporal or habitat isolation
- Ethological, behavioral, or sexual isolation
- Mechanical isolation
- Incompatibility
Which barriers are postzygotic?
- Hybrid inviability
- Hybrid sterility
- Hybrid breakdown
What are the limitations of the biological species concept?
- Cannot be applied to fossils.
- Cannot be applied to asexual organisms.
- Some organisms are morphologically and ecologically distinct, yet interbreed.
How does the morphological species concept characterize species?
Characterizes species by body shape and other structural features.
How does the ecological species concept characterize species?
In terms of their ecological niches.
How does the phylogenetic species concept characterize species?
Defines a species as the smallest group of individuals that share a common ancestor, forming one branch of the tree of life.
What happens in allopatric speciation?
A population forms a new species while geographically isolated from its parent population.
What happens in sympatric speciation?
A subset of a population forms a new species without geographic separation.
