Ch22 speciation Flashcards
speciation 2 parts
- the process of species formation.
- microevolutionary processes that alter the genetic and phenotyppic variation within populations. when these processes differ between populations the populations will diverge genetically and may become so different that we recognize them as different species.
morphological species concept
the concept that all individuals of a species share measurable traits that distinguish them from individuals of other species
biological species concept
the definition of species based on the ability of populations to interbreed and produce fertile offspring
phylogenetic species concept
a concept that seeks to describe species as the smallest group of populations that can be united by shared derived characters
subspecies
a taxonomic subdivision of a species
reproductive isolating mechanism
a biological characteristic that prevents the gene pools of 2 species from mixing
hybrid
an organism produced by mating between parents of different species or subspecies
prezygotic isolating mechanism
a reproductive isolating mechanism that acts before the formation of a zygote ( a fertilized egg)
postzygotic isolating mechanism
a reproductive isolating mechanism that acts after zygote formation
ecological isolation
a prezygotic isolating mechanism in which species live in the same geographical region occupy different habitats
temporal isolation
a prezygotic isolating mechanism in which species live in the same habitat but breed at different times of the day or year
behavioral (ethological) isolation
a prezygotic isolating mechanism in which 2 species do not mate because of differences in courtship behaviour
mechanical isolation
a prezygotic isolating mechanism caused by differences in the structure of reproductive organs or other body parts
Gametic isolation
a prezygotic isolating mechanism caused by incompatibility between the sperm of one species and the eggs of another species; may prevent fertilization
Hybrid inviability
a postzygotic isolating mechanism in which a hybrid individual has a low probability of survival to the reproductive age
hybrid sterility
a postzygotic isolating mechanism in which the hybrid offspring cannot form functional gametes
hybrid breakdown
a postzygotic isolating mechanism in which hybrids are capable of reproducing , but their offspring have reduced fertility or reduced valiability
allopatric speciation
the evolution of reproductive isolating mechanisms between 2 populations that are geographically separated
species fusion
merger of 2 populations into one after the establishment of secondary contact
secondary contact
the re-establishment of geographical overlap after a barrier that separated allopatric populations no longer keeps them apart
species cluster
a group of closely related species recently descended from a common ancestor
hybrid zone
a geographical are where the hybrid offspring of 2 divergent species / populations are common
reinforcement
the enhancement of reproductive isolation that had begun to develop while population were geographically separated
sympatric speciation
speciation that occurs without the geographical isolation of populations
host race
a population of insects that may be reproductively isolated from other population of the same species as a consequence of their adaptation to feed on a specific host plant species
polyploidy
(POLY was HAPpy with her Car)
the genetic condition of having one/more extra copies of the entire haploid complement of chromosomes
autopolyploidy
(PARENTS gave Carmen a Automobile)
the genetic condition of having more than 2 sets of chromosomes from the same parent species
unreduced gamete
a gamete that contains the same number of chromosomes as a somatic cell (46)
allopolypoidy
(Allo for Apart)
the genetic condition of having 2 or more complete sets of chromosomes from different parent species
ring species
a species with a geographical distribution that forms a ring around uninhabitable terrain
cline
a pattern of smooth variation in a characteristic along a geographical gradient
2 advantages of the morphological species concept
- practical way to identify species
2. can be applies to extincted fossilized organisms
3 disadvantages of the morphological species concept
- tells us little about the evolutionary processes that produced new species
- morphology doesn’t help distinguish some closely related species that are nearly identical in appearance
- difficult to apply morphology to variable species. if a species has polymorphism for example, then the phenotypic variation may lead the organisms being identified as different species (e.g European garden snails)
the biological species concept in Mayr’s words
“groups of interbreeding natural population that are reproductively isolated from (do not produce fertile offspring with) other such groups”
the biological species concept emphasizes 3 things
- the genetic cohesiveness of species
- same species experience gene flow
- species=large gene pool - genetic distinctive of each species
- different species=reproductively isolated, so cannot exchange genetic info - individuals of a species generally look a like
- same gene pool
3 advantages of the biological species concept
- species defined on basis of evolutionary concepts
- species=relatively easily to identify
- clear indication of process
2 disadvantages of the biological species concept
- doesnt work for life that reproduce sexually (e.g most bacteria)
- doesnt work for extincted life forms
phylogenetic species comprises population that share a ……
recent evolutionary history
3 advantages of the phylogenetic species concept
- can be applied to any organism (sexual and asexual)
- can be applied to extinct organisms
- distinctiveness of branches reflects lack of gene flow
2 disadvantages of the phylogenetic species concept
- evolutionary history of very few groups of organisms are known
- level of genetic distinctiveness used to define species is arbitrary (e.g. 70% similar are they a related species or not?)
many species exhibit substantial geographical variation…2 patterns
- ring species
2. clinal variation
5 types of prezygotic mechanisms
- ecological
- temporal
- behavioural
- mechanical
- gamete
3 postzygotic mechanisms
- hybrid inviability
- hybrid sterility
- hybrid breakdown
3 modes of speciation based on the geographical relationships as they become reproductively isolated
- allopatric speciation
- parapatric speciation
- sympatric speciation
allopatric speciation occurs in 2 stages
- population become geographically separated by a physical barrier
- population accumulate genetic differences that isolate them reproductively
- genetic drift= founder effect
- natural selection
- populations experience distinct mutations
secondary contact in allopatric speciation is when…..
barrier =eliminated or breached
secondary contact tests whether
populations have diverge enough to make them reproductively isolated. if the gene pools didnt differentiate much then species fusion will occur
4 properties of parapatric speciation
- speciation arising between adjacent populations
- may occur if hybrids have low relative fitness
- individuals colonise neighbouring habitat
- different genetic variants= favoured in each habitat
3 genetic mechanisms can lead to reproductive isolation
- genetic divergence between allopatric populations
- polyploidy in sympatric populations
- chromosome alterations
insects that feed on one/more plant species are likely to evolve by sympatric speciation forming…..
host races
genetic divergence in allopatric populations can lead to speciation in 3 processes
- postzygotic isolation accidental byproduct of …absence of gene flow accumulate genetic difference from: mutation, genetic drift and natural selection
- selection cannot promote isolating mechanisms directly in allopatry
- during secondary contact - reinforcement
polyploid individuals arise from 2 things
- autopolyloidy
2. allopolyploidy
