Biology - Isolating Mechanisms
Isolating megchanisms example : eagles
3 different types of eagle look very much alike but cannot interbreed
What do we call of the offspring from matings in which the individuals belong to substantially different gene pools
a hybrid
___________ is speciation that occurs in response to speciation in another species.
co- speciation
Although speciation is typically a lengthy process, it can occasionally occur in a single __________ , making it _________ by definition
generation, sympatric
ecological niche
is a complete description of the role the species plays in its environment—its habitat requirements
members of the same species can live in different places and therefore never ___________ with each other, ex. the Sri Lankan and Indian Asian elephants
mate
evolutionary species concept (EvSC)
members of a species all share a common ancestry and a common fate, requires that all members of a species are descended from a single common ancestor
morphospecies concept
members of the same species usually look alike, but not an infallible way to identify species
genetic speciation is ___________- by gene flow
retarded
the hypothesis of sympatric speciation
the creation of two species from one in the same environment can split into two without the benefit of geographical barriers to prevent interbreeding, very hard to prove
Speciation
the development of reproductive isolation between populations—is, therefore, just a by-product of the genetic divergence of separated populations.
gynognesis
the reporduction of females, sperm from male diploids to stimulate egg division but no genetic recombination.
reduced hybrid viability
very common, 2 gene pools that are fairly separate can mate, but it doesn't happen quite as expected. offspring will be inviable and will have low fitness ex. the mule. very strong, but cannot reproduce
Examples of hybrids in salamanders
The california tiger salamander and tha asian salamander produce a hybrid that has a higher fitness than either of the parents
Ring species
contain populations that are reproductively isolated from each other but can still exchange genetic material via other linking populations.
Factors that cause ________ __________ are generally divided into two categories: pre-zygotic isolating factors and post-zygotic factors
reproductive isolation
Natural selection can enhance ______________- ____________
reproductive isolation
_____ _______ and _______________complicate the BSC.
ring species, hybridization
Temporal isolation
seperation by time
Eastern and Western Wood-pewees are an example of ___ __________ because they hae overlapping traits.
sibling species. They cannot really be told apart but they can tell each other apart
divergence is closely tied to the idea of __ _______
gene flow
hybrid breakdown
generation skipping, some first generation hybrids are fertile and viable but when they mate with themselves or with either of the two parental species, the resulting offspring are weak or infertile ex. corn grandfather effect
taxonomy - if two species are enough alike, they're paced in the same _________________
genus
vicariance,
geographic barrier arises within a single population, separating it into two or more isolated populations.
In many cases of hybridization, __________ numbers may change
chromosome
Allfred Russel Wallace's definintion of species commonly used today:
Merely those strongly marked races or local forms which when in contact do not intermix, and when inhabiting distinct areas are generally believed to have a seperate origin, and to be incapable of producing a fertile hybrid offspring
adaptive radiation
a bout of unusually rapid evolutionary diversification in which natural selection accelerates the rates of both speciation and adaptation. Adaptive radiation occurs when there are many ecological opportunities available for exploitation
Pre-zygotic isolating factors
act before the fertilization of an egg, prevent fertilization from taking place
postzygotic
after fertilization, seperate gene pools, mating occurs and mix of genetic material between two individuals, reduced viability, reducied fertility hybrid breakdown
most speciation is ____________
allopatric
Courtship of the blue spotted salamander and Jefferson salamander include:
appraoch, contact, nudging, tail-fanning routines. female follows male, picks up desposited spermatophore, and stores for fertilization
The BSC does not apply to ________or ________ organisms.
asexual , extinct
____________-___________ is a powerful mechanism for generating genetic differences that lead to speciation
assortive mating
post-zygotic factors
come into play after fertilization, result in the failure of the fertilized egg to develop into a fertile individual
prezygotic
beofre fertilization. when mating does not occur, it prevents mating, affects habitat, time, behavior. when mating occurs, it affects mechanical and gametic stuff
The ____ is the best way to describe a species
biological species concept (BSC)
ecological species concept (ESC),
dea that there is a one-to-one correspondence between a species and its niche
the biological species concept
defining species is hard, must be by definition, fluid and capable of changing. to test whether or not species are real, we can plot measurements of charactersitics on a graph
_____________ and _____________ can extend the BSC
ecology, evolution
partially reproductively isolated
enetically diverged but not diverged far enough for full reproductive isolation, 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.
The blue spotted salamandar and he jefferson salamander have come ino contact and __________ to produce ___ populations
imbreed, hybrid
hybridization
interbreeding, mating that mixes two gene pools
selection tries to separate gene pools if the hybrid will have ______ fitness than the parents
lower
In the case of the salamanders, when there are _________ females, it is an indication of the presence of _________ of the species
more , hybridization
speciation can occur in the presence or absence of _____ ___________, and_______-- ___________- does not always lead to _____.
natural selection, natural selection, speciation
behaviorally isolated
ndividuals only mate with other individuals based on specific courtship rituals, songs, and other kinds of behaviors
Behavioral isolation
no mating based on behavior ex. blue-footed booby. if males feet arent blue enough, the female won't mate with him. ex. 2. the jumping spider male courtship behavioor prevents even very closely related species from interbreeding
allopatric populations
populations that are geographically separated from each other.
sympatric
populations that are in the same geographic location
Habitat isolation
prevents a gene pool from mating by seperating the habitats, sleelction tries to speerate gene pools if the hybrid will have lower fitness than the parents
two groups of isolating mechanisms are ___________ and ____________
prezygotic and postzygotic
reinforcement
process by which diverging populations undergo natural selection in favor of enhanced pre-zygotic isolation to prevent the production of less fit hybrid offspring
speciation occurs when two populations are unable to_________________________________________
produce viable, fertile offspring
Possible outcomes of isolated population divergence
reinforcement - something drives them apart quickly fusion - blend into one gene pool stability - hang around, and not going anywhere
how did shape divergence play a role in sticklebacks living in different types of lakes?
some became slender because they lived off of plankton, some became deeper nas a result of strong predation
dispersal
some individuals colonize a distant place, such as an island, far from the main source population
mechanical isolation
very common, there are two different species that will try to mate but cannot. ex. two species of dragonfly. males part wont' fit. it can be costly because they keep trying and get no where. another example: plants arrange parts in different places.
Gametic isolation
very common. when females release a bunch of egg and males release a bunch of sperm, the sperm has to match the egg in order for fertilization to occur.
What is the shortcoming of the BSC?
you would have to test if individuals were of the same species by forcing them to attempt to mate which takes time and recources that you may not have, it overlooks some organisms