Origin of Species Flashcards
Macroevolution
- is the broad pattern of evolution above the species level
- is changes over time in allele frequencies in a population
What is an example of macroevolution?
the origin of eyes capable of producing a focused image in both invertebrates and vertebrates
What are examples of microevolution?
- the spread of antibiotic resistance within a population of bacteria
- decrease in the prevalence of the sickle-cell allele in populations outside the range of mosquitoes that transmit malaria
- selection against a form of albinism caused by a genetic change at a single locus
Biological Species Concept
holds that populations belong to the same species if they can contribute genes to a common gene pool
What do reproductive barriers do?
they block gene flow between different species
What is the criteria for the biological species concept?
- ability to create viable
- fertile offspring
What is an advantage of biological species concept?
- objective criteria
- meshes well with gene flow concept
What is a disadvantage of biological species concept?
not applicable to extinct or asexual species
What is the criteria for morphological species concept?
similarities in body structure
What is an advantage of morphological species concept?
- easy to apply
- works for asexual and extinct species
What is a disadvantage to morphological species concept?
researchers may disagree on which structures are important
What is the criteria for phylogenetic species concept?
common evolutionary history
What is an advantage to phylogenetic species concept?
- based on actual relationships
- works for asexual and extinct species
What is a disadvantage to phylogenetic species concept?
requires good evolutionary histories
Behavioral Isolation
differences in mating rituals or displays
Is behavioral isolation pre-zygotic or pos-zygotic reproductive barrier?
pre-zygotic
What is an example of behavioral isolation?
different bird species display feathers of different colors during mating display
Temporal Isolation
differences in the timing of mating
Is temporal isolation a pre-zygotic or post-zygotic reproductive barrier?
pre-zygotic
What is an example of temporal isolation?
one plant species flowers before dawn while a related species flowers in the late afternoon
Habitat Isolation (reproductive barrier)
difference in habitat occupied
Is habitat isolation a pre-zygotic or post-zygotic reproductive barrier?
pre-zygotic
What is an example of habitat isolation?
different ticks live on different host species
Mechanical Isolation (reproductive barrier)
reproductive structure incompatibility
Is mechanical isolation a pre-zygotic or post-zygotic reproductive barrier?
pre-zygotic
What is an example of mechanical isolation?
differently shaped snail shells prevent alignment of genital openings
Gametic Isolation
sperm and egg are incompatible
Is gametic isolation pre-zygotic or post-zygotic reproductive barrier?
pre-zygotic
What is an example of gametic isolation?
different coral species release gametes into the water (but only gametes of conspecifics can fuse)
Reduced Hybrid Viability (reproductive barrier)
hybrid offspring are produced but are feeble or unable to compete for mates
Is reduced hybrid viability pre-zygotic or post-zygotic reproductive barrier?
pos-zygotic
What is an example of reduced hybrid viability?
two species of fish successfully interbreed but their offspring don’t live to maturity
Reduced Hybrid Fertility (reproductive barrier)
hybrid offspring are produced but are sterile
Is reduced hybrid fertility pre-zygotic or post-zygotic reproductive barrier?
post-zygotic
What is an example of reduced hybrid fertility?
horses can be mated with zebras (but their offspring are sterile)
Genetic Drift
- is a random change in allele frequencies over time
- is due to chance events that alter allele frequencies
Why are large finches now living on the Galápagos Islands different from the original source population from a nearby island?
- genetic drift occurred in the two populations
- natural selection favored individuals that were more fit in the new environment
- the separation of habitats reduced gene flow between the populations
Reinforcement (disruptive selection)
- is a type of natural selection
- which favors extreme phenotypes over intermediate phenotypes
Allopatric Speciation
- occurs when a species separates into two separate groups which are isolated from one another
How long does it take new species to form on Earth?
the time required varies considerably
Natural Selection Effects
- consistently causes a population to become better adapted to its environment
- a result of differential success in reproduction
- cannot cause a harmful allele to become more common
Genetic Drift Effects
- can result from the founder effect
- can result from the bottleneck effect
- causes allele frequencies to fluctuate randomly
Gene Flow Effects
- can introduce new alleles into a population’s gene pool
- a result of the movement of fertile individuals or their gametes
Disruptive Selection
- eliminated phenotypes near the average and favors the extreme phenotypes
- resulting in increased genetic variation in a population
What is the result of heterozygote advantage?
more genetic variation in the population
Directional Selection
- drives the average of the population in one direction
- when individuals with traits on one side of the mean in their population survive better or reproduce more than those on the other
Stabilizing Selection
- causes no change in the average of the population
- extreme phenotypes become less common
What is an adaptation?
a structure or function that is advantageous in a particular environment
What is an example of an adaptation?
ground-trunk anoles have evolved long legs that enable them to dart down from a tree trunk and catch prey on the ground with minimum vulnerability to predators
Define a species
is a group of individuals that can mate and produce fertile offspring together
