Macroevolution Flashcards
Define species
related organisms that maintain distinct set of traits in nature
What is a species concept?
approach to distinguish one species from another
Morphological Species Concept
based on physical characteristics
pros: applied to asexual organisms and extant and extinct organisms
cons: variation, sexual dimorphism
Ecological Species Concept
occupies an ecological niche
pros: applied to asexual organisms and extant and extinct organisms
cons: variation within species, niches are difficult to define
Phylogenetic Species Concept
described as the smallest group of organisms that share a common ancestor
pro: applied to asexual organisms and extant and extinct organisms
cons: variation
Biological Species Concept
based on potential to interbreed
pro: easy to define, easy to measure
cons: cannot be applied to asexual organisms and extant and extinct organisms
Requirements for Speciation
- Microevolution
2. Reproductive Isolation
Reproductive Isolating Mechanisms
- Prezygotic Isloating mechanism
2. Postzygotic Isolating mechanism
Habitat Isolation
Prezygotic; occurs due to a geographic barrier or habitat choice that prevents contact
Temporal Isolation
Prezygotic; reproduce at different times (day/year)
Behavioral Isolation
Prezygotic; traits associated with mate choice (song)
Mechanical Isolation
Prezygotic; morphological features prevent successful mating
Gametic Isolation
Prezygotic; gametes fail to unite (fertilization unsuccessful)
Hybrid Inviability
Postzygotic; eggs fertilized but impaired embryonic development or survival in environment
Hybrid Sterility
Postzygotic; interspecies hybrid is viable, but sterile
Hybrid Breakdown
Postzygotic; hybrids viable and fertile, but subsequent generations have decreased fitness
Modes of Speciation
- Allopatric Speciation
2. Sympatric Speciation
Allopatric Speciation
geographic barrier impedes interbreeding between populations (canyon); population could move to a new geographic region; split into 2 populations; raised isolated in different environments; merged populations=assortative mating
Sympatric Speciation
no geographic barrier impedes gene flow between populations
- Polyploidy–> chromosomal alteration in which an individual possesses more than 2 chromosome sets
- Habitat Differentiation–> populations diverge due to adaptations (habitat isolation or temporal isolation)
- Sexual Selection–> reproductive isolation results from divergence in mate choice (behavioral isolation)
Hybrid Zone
region where 2 species produce hybrids
Gradualism
new species evolve continuously through time
Punctuated equilibrium
species remain unchanged for many generations punctuated by rapid periods of change
