Speciation Flashcards
Lesson 12
What is speciation?
the origin of new species, is at the key point where microevolution and macroevolution intersect
How many species exist?
Known: 2-3 million
Estimated: 5-100 million
What is a species?
Members of a biological species are reproductively compatible, at least potentially; they cannot interbreed with other populations
How do new species originate from existing ones?
A reproductive barrier to gene flow is established, making the populations diverge genetically (allele frequencies) and making them reproductively isolated
What is reproductive isolation?
the existence of biological factors (barriers) that impede two species from producing viable, fertile hybrids
What is the biological species concept?
Species are groups of actually or potentially inbreeding populations, which are reproductively isolated from other such groups
What are prezygotic barriers?
Temporal or Habitat Isolation- potential mates don’t meet
Ethological, Behavior, or Sexual Isolation- potential mates meet but do not mate
Mechanical Isolation- Copulation occurs, no gamete transfer
Incompatibility- Gametes are transferred, no fertilization
What are postzygotic barriers?
Hybrid Inviability- Fertilization occurs, but F1 hybrid has reduced viability
Hybrid Sterility- F1 hybrid viable, but has reduced fertility
Hybrid Breakdown- Reduced viability/fertility in F2 or backcross hybrids
What are the premating barriers?
Temporal or Habitat Isolation, Ethological, Behavioral or Sexual Isolation
What are the postmating barriers?
Mechanical Isolation, Incompatibility, Hybrid Inviability, Hybrid Sterility, Hybrid Breakdown
What are some limitations of the biological species concept?
Can’t be applied to fossils
Can’t be applied to asexual organisms
Some organisms are morphologically and ecologically distinct, yet interbreed
What is the morphological species concept?
Morphological species concept- characterizes species by body shape and other structural features
What is the ecological species concept?
Ecological species concept- characterizes species in terms of their ecological niches
What is the phylogenetic species concept?
Phylogenetic species concept- defines a species as the smallest group of individuals that share a common ancestor, forming one branch of the tree
What is allopatric speciation?
A population forms a new species while geographically isolated from its parent population
ex: snapping shrimp and Hawaiian fruit flies
What is sympatric speciation?
A subset of a population forms a new species without geographic seperation
What can cause sympatric speciation?
habitat differentiation (usually through selection)
Polyploidy (mutation)
Sexual selection (blue and orange fish example)
How does sympatric speciation via autopolyploidy occur?
Both chromosome sets are derived from the same species
How does sympatric speciation via allopolyploidy occur?
The chromosome sets are derived from different species
What are hybrid zones?
Regions where members of different species with incomplete reproductive barriers mate and produce hybrids
What are the possible outcomes of hybrid zones?
Reinforcement (natural selection increase reproductive isolation, strengthen reproductive barriers)
Fusion (the species interact with each other again, weaken reproductive barriers)
Stability (no change in species interactions, continued formation of hybrid individuals)
What does the flowers example represent in respect to speciation?
In other organisms, speciation can be influenced by larger numbers of genes and gene interactions
What is the tree of life?
Idea that all organisms on earth are related to each other via a gigantic tree of common descent
