Ch. 13 The Origin Of Species Flashcards
The distinction between “definition” and “recognition” is similar to the distinction between..
The formal description of a species and the diagnosis of a species
Phenetic characters
All the observable or measureable characters of an organism, including microscopic and physiological
Formal definition
Description of a species, using phenetic characters
Phenetic species
Definition based on clustering of physical characters
Typological species
Definition based on similarity to a type specimen or ideal type
Reproductive species
Definition based on reproductive isolation
Ecological species
Definition based on niche
Non-temporal species concepts
Phenetic species
Typological species
Reproductive species
Ecological species
Temporal species concepts
Cladistic species
Evolutionary species concept
Cladistic species
Definition based on segment of phylogenetic tree
Evolutionary species concept
Definition based on vague “tendencies”
Biological species concept
- Species are groups of interbreeding populations that are reproductively isolated from other such groups
- Ernst Mayr
- most widely accepted definition for species
- species are unified by gene flow within a common gene pool
Phylogenetic species concept
Smallest possible group descending from a common ancestor and recognizable by unique, derived traits
Interbreeding between species is prevented by what?
Isolating mechanisms
Isolating mechanisms
Serve to prevent interbreeding and thereby establish reproductive isolation of populations
Isolating mechanisms can be categorized as either ___ or ___.
Premating (prezygotic)
Postmating (postzygotic)
Premating isolating mechanisms prevent what?
Prevent mates from two separate populations from getting together
The most basic of premechanisms involve one or another variation on ___
Allopatry
Allopatry
Geographic separation, habitat separation, seasonal or temporal separation
More complicated premating mechanisms involve..
Behavior, biomechanics, or gamete interaction to prevent gametes from coming together
Geographic separation
Populations are geographically separated
Habitat separation
Populations occur in different habitats in the same general region
Seasonal or temporal separation
- mating or flowering occur in different seasons
- separation of photosynthesis and nitrogen fixing
Cline
Gradual change in the species phenotype and genotype frequencies through a series of geographically separate populations
Premating barriers
- timing of reproduction
- pollinator isolation
- mismatched morphology
Gametic incompatibility
Sperm or pollen from one species fails to penetrate and fertilize the egg of another species
Haldanes rule
In species with genetic sex determination, reduced viability or fertility is mucho more common in the heterogametic sex
Postzygotic barriers
Hybrids are produced but have low fitness
- hybrid inviability
- hybrid sterility
- ecological inviability
- behavioral sterility
recognition species concept
Species is defined by mutual recognition of suitable mates among the members of a population
Ecological species concept
Places an emphasis on niche or adaptive zone
Competitive exclusion
Two or more species cannot occupy the same niche
One is better and beats other out
Character displacement
Similar species which share a common resource will diverge from one another
Causes of speciation
- geographic isolation
- reduction of gene flow
Allopatric speciation: the great divide
Allo = other
Patric = place
Speciation by geographic isolation
Islands provide opportunity for ___ speciation
Allopatric
Ring species
Populations at ends can no longer interbreed
Peripatric speciation
Peri = near
Patric = place
A small population isolated at the edge of a larger population
Sympatric speciation
Sym = same
Patric = place
New niche
Parapatric speciation
Para = beside
Patric = place
Individuals are more likely to mate with their geographic neighbors than with individuals in a different part of the populations range
Parapatric speciation begins with the evolution of a ..?
Hybrid zone
Bacterial species often defined by what?
Specific adaptations
Horizontal gene transfer makes ___ difficult
Classification
General lineage species concept
Species are metapopulations that exchange alleles frequently enough to comprise the same gene pool
