Speciation Flashcards
origin of the word “species”
specere (Latin)
means kind or appearance
species is a modern classification system used to describe each organism on Earth, including its:
evolutionary history
morphological and genetic characteristics
its relatedness to other organisms
what did scientists Theodosius Dobzhansky and Ernst Mayr build as criteria for each species?
interbreeding
what is a species
a group of individuals capable of mating and producing fertile offspring
what make species “species”?
if individuals interbreed and produce fertile offspring only among themselves
the members of each species resemble each other and are structurally different in some respects from the members of any other species
does a change in gene frequency within a gene pool, either by means of genetic drift or natural selection, considered evidence of evolution, and does it constitute speciation?
a change in gene frequency is considered evidence of evolution but does not constitute speciation
define biological species concept
a species is a population or group of populations that are able to interbreed, under natural conditions, to produce fertile offspring
does the biological species concept apply to all life forms?
no
the biological species concept defines speciation in terms of sexual reproduction. not all life forms undergo sexual reproduction. some undergo asexual reproduction (binary fission, spore formation, budding, fragmentation, regeneration, vegetative propagation)
define speciation
the process by which an ancestral species splits into 2 or more new species
what is the result of speciation?
development of new species with unique characteristics
what are the 3 main stages of speciation?
separation
divergence
isolation
the first stage of speciation: separation
original species are separated into two or more groups that are prevented from interbreeding, thus restricting gene flow between them
the second stage of speciation: divergence
the independent accumulation of heritable genetic mutations and differential survival and reproduction of individuals based upon heritable traits
the third stage of speciation: isolation
groups reunite and are unable to breed and produce viable offspring
how is speciation completed?
if biological characteristics result in the evolution of mechanisms that prevent interbeeding
explain the experiment by Diane Dodd (1989)
two groups of a species of fruit fly were separated and bred for 35 generations. One of the groups was given a source of food containing maltose while the other group had fructose instead. After 35 generations the two groups were brought back into contact with one another and yet members of the two groups would not mate with one another or reproduce - even in situations where it was the only way to produce offspring.
what are the 4 types of natural speciation?
allopatric speciation
peripatric speciation
parapatric speciation
sympatric speciation
allopatric speciation
the result of the physical separation of populations
peripatric speciation
a subform of allopatric speciation in which a very small segment of individuals is physically separated from the original population
parapatric speciation
a very slow process by which populations separated by occupying a different ecological niche in a very large geographic region
sympatric speciation
the formation of new species from populations of the original species that occupy the same geographical location
artificial speciation
when scientists separated members of the same species into populations that form distinct species as a result of selective breeding
speciation that occurs as a result of physical separation
allopatric speciation
steps of allopatric speciation (4)
- geographic barrier such as an ocean, mountain, or earthquake that physically separates populations of the original species
- the two populations accumulate heritable mutations and experience different selective pressures
- the two populations become increasingly divergent until reproductively incompatible
- speciation is complete when interbreeding with fertile offspring is no longer possible
the most famous example of allopatric speciation
Galapagos Island finches, reported by Charles Darwin
small groups of individuals break off from the larger group and form a new species, one group is much smaller than the other
peripatric speciation
maintain a zone of contact and do not cease the exchange of genes completely
parapatric speciation
evolve into distinct species while maintaining contact along a common border
adjacent populations
speciation that occurs in the same area
sympatric speciation
an example of sympatric speciation
Cichlid fish in Lake Apoyegue, Nacaragua
the process by which an ancestral species splits into 2 or more new species
speciation
the separation of different species to keep them from creating offspring by preventing the gametes from forming a zygote; before the fertilized egg
prezygotic barriers
occurs after the gametes have made a zygote through fertilizing the egg; after the fertilized egg
postzygotic barrier
what are the 5 prezygotic isolation mechanisms?
spatial isolation
temporal isolation
mechanical isolation
gametic isolation
behavior isolation
isolation based on physical distance
spatial isolation
isolation based on reproductive timing
temporal isolation
isolation based on lack of fit between sex organs
mechanical isolation
isolation based on a lack of compatability of gametes
gametic isolation
isolation based on mating rituals or behaviors
behavioral isolation
