speciation Flashcards
speciation
formation of new species
speciation can occur when members of a species no longer
reproduce with each other
lack of gene flow allows species to
become different
biological species concept
population that can naturally reproduce to produce FERTILE offspring
according to biological species concept, species share
a single large gene pool
limitations to biological species concept
-difficult to determine gene flow
-does not work for asexual organisms
morphological species concept separates species by
body shape and structure
enological species concept separates species by
how they interact with their environment
ecological species concept emphasized … of each species
living requirements
_____ _____ is required to form truly distinct biological species
reproductive isolation
to form distinct species, enough differences must develop so that species can no longer
breed with each other
two forms of reproductive barriers
-prezygotic barriers
-postzygotic barriers
prezygotic barriers
prevents species form successfully attempting to reproduce
habitat isolation (prezygotic barrier)
species are never in same place
behavioral isolation (prezygotic barrier)
methods of attracting a mate are different
temporal isolation (prezygotic barrier)
reproduce at different times
mechanical isoltion (prezygotic barrier)
reproductive organs are not compatible
gene isolation (prezygotic barrier)
proteins on egg and sperm don’t match
post zygotic barriers
prevent growth in a viable fertile adult
hybrid
offspring of two Dif species
hybrid inviablility (postzygotic barrier)
embryo cannot complete development because genetic instructions are incomplete
hybrid sterility (postzygotic barrier)
hybrid cannot produce gametes (sometimes due to odd number of chromosomes)
hybrid reduced offspring viability (postzygotic barrier)
offspring of hybrids do not survive well
3 steps needed for speciation
Isolation of populations of species
Changes in gene pools of the isolated species
Creation of reproductive isolation between populations
allopatric speciation
physical barrier or distance blocks gene flow between 2 populations (physically isolated from each other)
sympatric speciation
occurs in SAME location
-nonphysical reproduction isolation prevents gene flow
examples of sympatric speciation barriers
-reproduce at Dif times
-live in Dif parts of environment
-sudden genetic change in 1 population
polyploidy
doubling number of chromosomes
example of sympatric speciation in maggot flies
Several populations live in same area
Some live on apple trees, some live on hawthorn shrubs
Flies mate when plant produces fruit
Hawthorn and apple trees produce fruit 1 month apart
Very little genetic flow between hawthorn and apple flies since they don’t mate at the same time
Apple and hawthorn populations different strongly in the frequency of some alleles
polyploidy results from mistakes when
cells divide
polyploidy occurs mostly in
plants (can evolve fast by doubling genetic material)
polyploidy instantly results in
a new species
can new species resulting from polyploidy reproduce with original species?
NO, new species have different # of chromosomes
polyploidy can enable ____ plants to reproduce:
hybrid; Doubling the number of chromosomes fixes the problem of having an odd number of chromosomes
autopolyploid has more than …
2 sets of chromosomes from same species
how does autopolyploidy occur?
meiosis error can create diploid gametes and combination of 2n gametes produces 4n offspring
allopolyploid
hybrid between species
how can hybrid infertility be overcome?
double number of chromosomes again OR hybridize again with parent species
adaptive radiation is a mixture of
allopatric and sympatric speciation
hybrid zones help us tell that ___ occurred
speciation
what is a hybrid zone?
area where members of different species mate
hybrid zones: observed patterns
reinforcement, fusion and stability
reinforcement (hybrid zones)
strengthens or reinforces barriers to hybridization
example of reinforcement in hybrid zones
male species looks different from male of other species in only that area so that females can tell them apart
fusion (hybrid zones)
weakens barriers to hybridization (increases gene flow)
what might reverse speciation and result in 1 species again?
fusion
stability (hybrid zone)
-hybridization remains possible
-hybrids continue to be produced
