Origins of Species Flashcards
Can speciation occur with gene flow
NO
is gene flow a homologous or analogous force
homologous
speciation
divergence of 2 species that results in a macroevolution
what is at the focal point of evolutionary theory
speciation
evolutionary theory explains
how new species originate and how populations evolve
true or false
the same mechanisms are used for microevolution and macroevolution
TRUE
the biological species concept is based on
the potential to interbreed rather than on physical similarities
what does the biological species concept emphasis
sexual reproduction
what are some limitations of the biological species concept
- asexual reproduction
- extinct species
- hybrids (caused by gene flow)
according to the Biological Species concept, what must offspring be to be the same species
fertile and viable
what are two issues/challenges with identifying species with the biological species concept
- species that look SAME but are DIFFERENT (cryptic species)
- Species that look DIFFERENT but are the SAME
other species concepts
- morphological SC
- lineage/phylogenetic SC
3.ecological species concept
morphological SC
according to appearance, species that look the same are the same
lineage/phylogenetic SC
a shared pattern of ancestry and descent is used to identify species
what is one benefit of the lineage/phylogenetic SC
it takes away the limitation of fossil/extinct species
how does speciation express “unity of life”
by helping to explain the features that many organisms share
what forms the conceptual bridge between microevolution and macroevolution
speciation
what is the primary definition of species
biological species concept
according to the BSC, would individuals make viable, fertile offspring with members of another group
NO
What holds the gene pool of a species together to cause its members to resemble each other
gene flow tends to hold the population together genetically
What can play a role in the formation of new species
reduction or lack of gene flow
what does the formation of a new species hinge on
reproductive isolation
reproductive isolation
Existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offspring
what is the result of the barriers in reproductive isolation
- blocking gene flow
- limits the formation of hybrids
hybrids
Offspring that result from an interspecific mating
how can reproductive barriers be classified
according to whether they contribute to reproductive isolation before OR after fertilization
two types of reproductive isolation barriers
- prezygotic barrier
- postzygotic barrier
prezygotic barrier
before the zygote
what reproductive barrier is this
blocks fertilization from occurring
prezygotic barrier
postzygotic barrier
after the zygote
what reproductive barrier is this
contributes to reproductive isolation AFTER the hybrid zygote is formed
postzygotic barrier
three ways prezygotic barriers can work
- Impeding members of different species from attempting to mate
- Preventing an attempted mating from being completed successfully
- Hindering fertilization if mating is successful
five methods for how prezygotic barriers inhibit fertilization
- habitat isolation
- temporal isolation
- behavioral isolation
- mechanical isolation
- gametic isolation
what reproductive barrier is this
habitat isolation
prezygotic
what reproductive barrier is this
temporal isolation
prezygotic
what reproductive barrier is this
behavioral isolation
prezygotic
what reproductive barrier is this
mechanical isolation
prezygotic
what reproductive barrier is this
gametic isolation
prezygotic
what reproductive barrier is this
reduced hybrid viability
postzygotic
what reproductive barrier is this
reduced hybrid fertility
postzygotic
what reproductive barrier is this
hybrid breakdown
postzygotic
habitat isolation
Two species that occupy the same habitats may encounter each other rarely if at all
true or false
in habitat isolation the species are separated by a PHYSICAL barrier
FALSE
temporal isolation
species that breed during different times o day, seasons or years cannot mix gametes
behavioural isolation
Courtship rituals that are unique to different species
what enables mate recognition
behavioral isolation barrier
mate recognition
a way to identify potential mates of the SAME species
mechanical isolation
mating is attempted but MORPHOLOGICAL differences prevent successful completion
gametic isolation
sperm of one species is NOT able to fertilize the egg of another species
what are 3 postzygotic barriers
- reduced hybrid fertilization
- reduced hybrid viability
- hybrid breakdown
reduced hybrid fertilization
Genes of different parent species interact in ways that impair the hybrid’s development or survival
reduced hybrid viability
when hybrids are sterile there is NO gene flow between species
hybrid breakdown
when viable and fertile first generation hybrids mate with another of either parent species the offspring of the next-gen would be STERILE
true or false
the morphological SC can be applied to asexual and sexual organisms
YES
what is a disadvantage of morphological SC
relies on subjective criteria
ecological species concept
views a species in terms of its ecological niche and how its different
ecological niche
the sum of how members of the species interact with nonliving and living parts of their environment
main two ways new species forms
- allopatric speciation
- sympatric speciation
allopatric speciation
populations are geographically isolated
sympatric speciation
populations are NOT geographically isolated
how is gene flow interrupted in allopatric speciation
when a population is divided into geographically isolated subpopulations
How formidable must a geographic barrier be to promote allopatric speciation
depends on how mobile a species is (smaller rodents would find a wide river more of a barrier than birds)
in allopatric speciation, reproductive isolation is a by-product of
genetic divergence from selection or drift
what is the importance of allopatric speciation
Regions that are isolated or highly subdivided by barriers typically have more species than similar regions that lack such features
true or false
reproductive isolation decreases as the geographic distance between populations increases in allopatric speciation
FALSE, it increases as distance increases
what barrier prevents interbreeding when members of different populations meet (after allopatric speciation)
BIOLOGICAL
sympatric speciation occurs when
populations live in the SAME geographic area
How can reproductive barriers form between sympatric populations while members remain in contact with each other
if gene flow is reduced by factors such as
1. polyploidy
2. sexual selection
3. habitat differentiation
true or false
allopatric speciation is LESS common than sympatric speciation
FALSE, sympatric speciation is less
polyploidy
species originating from an accident during cell division that results in extra sets of chromosomes
is polyploidy more common in plants or animals
plants
two types of polyploidy
- autoploid
- allopolypoidy
autoploid
an individual that has more than two chromosome sets derived from a single species
allopolyploid
a sterile hybrid changes into a fertile polyploid
why are most hybrids sterile?
set of chromosomes from one species cannot pair during meiosis with those from the other species
why are most hybrids sterile?
set of chromosomes from one species cannot pair during meiosis with those from the other species
sexual selection
females select males based on their appearances
habitat differentiation
when genetic factors enable a subpopulation to exploit a habitat/resource NOT used by the parent population
3 ways sympatric speciation can occur
- polyploid
- sexual selection
- habitat differentiation
What happens if species with INCOMPLETE reproductive barriers come into contact with one another
formation of a hybrid zone
hybrid zone
Region in which members of different species meet and mate = produce some offspring of mixed ancestry
true or false
hybrids are ALWAYS used as a stepping-stone for alleles to be passed from one species to another
FALSE, they are rarely used for this
hybrid zones are typically located
where the habitat of interbreeding species meet
Once formed, how does a hybrid zone change over time
A change in environment can alter where the habitats of interbreeding species meet = causes existing hybrid zone to move to a new location
Three outcomes for the hybrid zone over time if the hybrids DON’T become reproductively isolated
- reinforcement of barriers
- fusion of species
- stability
Reinforcement is the ________ reproductive barriers
strengthing
true or false
hybrids are often MORE fit than members of the parent species
FALSE
Reinforcement
natural selection would strength prezygotic barriers to reproduction (reducing formation of unfit hybrids)
would reinforcement cause the reproductive barrier between species to be stronger for ______ populations THAN for ________ populations
sympatric AND allopatric
fusion causes ______ of reproductive barriers
weakening
why would fusion cause the weakening of reproductive barriers
Gene pools for the two species would become increasingly alike if reproductive barriers weakened further with lots of gene flow = fusion into ONE species
stability is the ________ formation of hybrids
continued
if hybrid zones are stable then they
continue to produce hyrbids
what are two outcomes for a stable hybrid zone
- hybrids survive better than parent species
- hybrids are selected against
what two things does evolution by natural selection explain
- diversity of life
- adaptations of organisms
Punctuated equilibria
describes periods of apparent stasis punctuated by the sudden change
punctuated model
New species change most as they branch from a parent species and then change LITTLE for the rest of their existence
does speciation occur rapidly in the punctuated model
YES
gradual model
Species diverge from one another more slowly and steadily over time
TRUE or FALSE
can we tell WHEN a biological species is formed with gradual model
NO, info doesn’t fossilize
______ periods cannot be distinguished in fossil strata
short time periods
when can new species arise radiply
once divergence begins
What is the total length of time between speciation events?
time elapsed before populations of a newly formed species start to diverge PLUS time it takes for speciation to be complete once divergence begins
Speciation begins only AFTER
gene flow between populations is interrupted AND the populations diverge until they become reproductively isolated
is this the punctated or gradual model
gradual model
is this the punctated or gradual model
punctuated
barriers prevent gene flow in ______ species
diverging
when can natural selection, genetic drift and mutation act on a separate population
AFTER speciation
what is the first step towards micro/macroevolution
gene flow stops between populations
Can speciation occur with gene flow?
NO
