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