module 8 Flashcards
speciation forms what
a conceptual bridge between microevolution and macroevolution
what is an example of macroevolutionary change
origin of new groups of organisms such as mammals or flowering plants through a series of speciation events
species in terms of macroorganism
group of organisms that produce valuable fertile offspring under natural conditions
reproductive isolation
barriers prevent members of two species from producing viable fertile offspring
what could be a reason for reproductive isolation
could. be mating timeline differs or traits differing
what could happen to a hybrid that is born
can be less happy and not being able to reproduce
hybrid breakdown
anything inhibiting thriving after being born
species in terms of microorganism
genetically related enough (defined threshold) and fulfill same ecological roles
how do microbes reproduce
asexually
can speciation take place with or without geographic seperation
yes
allopatric speciation
Areas with divided barriers have more species (island chains)
-population forms new species while geographically isolated from the parent population
sympatric speciation
-less common and driven by sexual selection or utilization of a different food or habitat
no subset of species forms without geographic isolation
what could allopatric speciation be caused by
founder effect or river diverging
allo =
other
sym=
together
How can reproductive barriers form between sympatric populations while their members remain in contact with each other?
Although such contact (and the ongoing gene flow that results) makes sympatric speciation less common than allopatric speciation, sympatric speciation can occur if gene flow is reduced by such factors as sexual selection and habitat differentiation. (Note that sexual selection and habitat differentiation also can promote allopatric speciation.)
behavioral barrier
females prefer to mate with males of the same body shape
when can sympatric speciation occur
when a subpopulation exploits a habitat or resources not used by parent population
how long does it take for a new species to form (with focus on macroorganisms)
depends on species and environment
looking at opatterns in fossil records is known as
morphology
two models of morphology
punctuated model and gradual model
punctuated model
new species change most as they branch from a parent species and then change little for the rest of their experience
gradual model
species diverge from one another more slowly and steadily overtime
how long on average foes speciation in plants and animals take
it is highly variable but on average takes millions of years
how long is speciation in micorbes
much shorter in microbes due to fast generation time
how many genes influence the formation of new species
1, a few, or a lot can (enough to cause reproductive isolation)
in some cases what can reproductive isolation result fro
the effects of one gene or by many genes
how does the amount of genes that influence a new species differ in microbes
has less to do with how they reproduce but about their niche and function. more about genetic variation threshold (look at average nucleotide or RNA to classify bacteria)
