Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
53 Cards in this Set
- Front
- Back
speciation |
process that produces new and distinct forms of life |
|
the species problem |
the difficulty of defining species *the species, as an evolutionary unit, must by definition be fluid and capable of changing, giving rise through evolution to new species, but species are not fixed |
|
species |
fundamental evolutionary unit *ability (or inability) to exchange genetic material by producing fertile offspring |
|
Key to the biological species concept (BSC) |
reproductive isolation |
|
biological species concept (BSC) |
species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups
|
|
Requirement for BSC |
1. reproductively compatible 2. fertile offspring |
|
Shortcomings of the BSC |
1. asexual species 2. extinct organisms |
|
morphospecies concept |
members of the same species usually look alike |
|
Exceptions to the morphospecies concept |
1. polymorphisms (same species look different) 2. members of different species can look alike |
|
polymorphisms |
many forms |
|
What complicates the BSC? |
1. ring species 2 hybridization |
|
ring species |
species that are reproductively isolated from each other but can still exchange genetic material via other linking populations |
|
hybridization |
interbreeding between species |
|
What can extend the BSC? |
1. ecology 2. evolution |
|
ecological niche |
complete description of the role the species plays in its environment- its habitat requirements, its nutritional and water needs, and the like |
|
Ecological Species Concept (ESC) |
one to one correspondence between a species and its niche |
|
Evolutionary Species Concept (EvSC) |
members of a species all share a common ancestry and fate |
|
reproductive isolation |
inability to produce viable, fertile offspring |
|
Factors that cause reproductive isolation are generally divided into two categories: |
1. pre-zygotic 2. post-zygotic |
|
Pre-zygotic |
act before the fertilization of the egg; prevent fertilization from taking place 1. spatial isolation 2. temporal isolation 3. behavioral isolation 4. mechanical isolation |
|
Post-zygotic |
comes into play after fertilization; failure of the fertilized egg to develop into a fertile individual |
|
Behavioral Isolation |
individuals only mate with other individuals based on specific courtship rituals, songs, and other kinds of behaviors *mating dances and calls |
|
Mechanical Isolation |
"lock and key" physical or chemical incompatiblity |
|
Temporal Isolation |
different times |
|
Spatial Isolation |
1. geographic isolation (places) 2. ecological isolation (niches) |
|
Pozt-zygotic factors |
genetic incompatibility can mate, but offspring are not viable or sterile |
|
The more closely related a pair of species, ... |
the more genetically similar, the less extreme the genetic incompatibility between their genomes |
|
Speciation is a by-product of ... |
the genetic divergence of separated populations |
|
partially reproductively isolated |
not yet separate species, but the genetic differences between them are extensive enough that the hybrid offspring they produce have reduced fertility or viability compared to offspring produced by crosses between individuals within each population
|
|
allopatric speciation |
speciation that results from the geographical separation of populations "different place", physical separation |
|
subspecies |
further designation after its species name |
|
How do populations become allopatric? |
1. dispersal 2. vicariance |
|
dispersal |
individuals colonize a distant place, such as an island, far from the main source population |
|
vicariance |
geographic barrier arises within a single population, separating it into two or more isolated populations |
|
peripatric speciation |
a few individuals from a mainland population disperse to a new location remote from the original population and evolve separately
|
|
mainland population |
central population of a species |
|
island population |
distant, isolated that is geographically remote from the initial mainland population's habitat area |
|
Why does change accumulate faster in the peripheral isolate? |
1. genetic drift is stronger in smaller populations 2. environment may differ in a way that results in natural selection driving differences between the two populations |
|
adaptive radiation |
unusually rapid evolutionary diversification in which natural selection accelerates the rates of both speciation and adapation |
|
Adaptive radiation occurs when ... |
there are many ecological opportunities available for exploitation |
|
co-speciation |
speciation that occurs in response to speciation in another species |
|
sympatric populations |
speciation with gene flow between diverging populations "same place" |
|
Gene flow negates the _______ of populations. |
genetic divergence |
|
instantaneous speciation |
caused by hybridization between two species in which the offspring are reproductively isolated from both parents |
|
tetraploid |
double diploid |
|
polyploidy |
multiple chromosome sets; change in chromosome numbers between parent and offspring |
|
allopolyploids |
produced from hybridization of two different species |
|
autopolyploids |
derived from an unusual reproductive event between members of a single species |
|
Speciation can occur with or without ... |
natural selection |
|
Two ways in which natural selection can be involved in speciation: |
1. sympatric speciation requires some form of disruptive natural selection 2. allopatric speciation may be facilitated by natural selection |
|
Natural selection can enhance ... |
reproductive isolation |
|
reinforcement |
natural selection act on mutations that allows individuals to identify and mate with individuals more like themselves *strong in sympatric speciation |
|
If populations diverge without natural selection, what can it be the result of? |
genetic drift |