LO17 Flashcards
definition: defines a species as one or more populations whose members can interbreed and produce fertile offspring
biological species concept
according to the BSC members of one species are what from members of a different species?
reproductively isolated
What are some limitations of the BSC
- cannot be applied to asexual or extinct organisms
- different species occasionally interbreed
Why can’t the BSC be applied to asexual or extinct organisms?
Because it is impossible to know about interbreeding in extinct organisms
definition: evolution of new species
speciation
When does the speciation process begin?
When a population becomes reproductively isolated from other members of its species
definition: occurs when interbreeding is prevented between populations
reproductive isolation
What happens as a result of reproductive isolation?
The gene pools of the separated populations begin to diverge
What would happen when enough genetic differences accumulate?
Gene flow no longer occurs
What are the two types of speciation?
allopatric and sympatric
Natural selection, mutation, genetic drift, ad gene flow result in what?
microevolution and origin of new species
definition: occurs when a population becomes geographically isolated from other populations of its species
allopatric speciation
During isolation how does the population get genetic differences?
Due to different selective pressures, genetic drift, reproductively isolated
definition:occurs due to some type of geographic barrier or dispersal to a new location
gographic isolation
What is required for allopatric speciation to occur?
They need to be geographically isolated
definition: occurs when a new species evolves with the same geographic region as its parent species
sympatric speciation
definition: can lead to reproductive isolation in a single generation and has likely been the most significant factor in the evolution of flowering plants
allopolyploidy
definition: an individual with a nucleus containing more than two copies of each chromosome (>3)
polyploid
allopolyploidy occurs when what happens
polyploid arises
a common mechanism of sympatric speciation in flowering plants
allopolyploidy
Sympatric speciation is what in animals?
rare
Sympatric speciation is due to a change is what?
ecology
An example of speciation is what?
Lake Victoria
definition: prevents interbreeding between closely related species whose geographic ranges overlap
reproductive isolating. mechanisms
How do reproductive isolating mechanisms preserves species genetic integrity by what?
preventing gene flow
Most species have how many RI mechanisms?
one or two
Most RI mechanisms work before what?
before mating
definition: reproductive isolating mechanisms that prevent mating and/or fertilization
prezygote barriers
definition: reproductive isolating mechanisms that prevent gene flow after fertilization
postzygotic barriers
If reproductive barriers are not well developed what would happen?
hybridization
Prezygotic barriers prevent fertilization in what ways?
temporal, habitat, behavioral, mechanical, gametic
definition: when a closely-related species reproduce at different times of the year
temporal isolation
definition: when a closely-related species breed in different habitats in the same geographic area
habitat isolation
definition: closely related species use different courtship behaviors
behavioral isolation
definition:closely related species have incompatible reproductive organs
mechanical isolation
definition: closely related species have gametes that are incompatible due to molecular/chemical differences
gametic isolation
postzygotic prevent what from being made as a result of hybridization
viable offspring
definition: hybrid embryos die during development
hydbring inviability
definition: interspecific hybrids do not reproduce successfully
hybrid sterility
definition: the offspring of F1 hybrids cannot reproduce beyond one or a few generation or have reduced fitness
hybrid breakdown
What is reason that inviability happens?
Because developmental signals dont interact properly
What is a reason that sterility happens?
because different chromosome numbers
How do evolutionary novelties rise?
Modification of structures already in existence
definition: a structure that a group of organisms already possessed that become modified as it adapt to a new role
preadaptation
example of a preadaptation
feathers for flight
most preadaptations arise due to what?
mutation in genes that control development
What would be the effect of a few mutations in a development gene.
They can have significant phenotypic effect
definition: occurs when there is an evolutionary diversification of many species from one or a few ancestral species over a short period of time
adaptive radiation
What happens to species diversity during extinction?
They decrease in the short term
definition: continuous low-level of extinction that is always occuring
background extintion
definition: large numbers of species and higher taxonomic groups are killed off over a period of time
mass extinction
Why do mass extinctions happen?
because a major environmental catastrophe
examples of adaptive radiation include what?
galapagos finches adapting to different island habitats
Allopatric speciation examples include what?
- The isthmus formed separating marine populations
- Porto santo rabbits becoming a new species after released on isolated island
- Pupfish in Death valley lake split into 20 different species
