the origin of species Flashcards
macroevolution
evolution of new species
speciation
origin of a new species
what 2 processes lead to speciation?
anagenesis (phyletic evolution)
cladogenesis (branching evolution)
anagenesis
accumulation of changes transforming one species into another species
cladogenesis
budding of one or more new species from a parent species that can continue to exist
what did Linnaeus describe species in terms of?
morphology - their physical form
what does taxonomy consider differences in today?
body function, biochemistry, behavior, and genetic makeup (DNA)
biological species concept
defines a species as a population who can interbreed in nature to produce viable, fertile offspring with each other and not those with members of other species
what is the exception to the biological species concept?
in zoos or in labs where hybrids are sometimes produced between species that do not interbreed in nature
prezygotic barriers
reproductive barriers that isolate gene pools that happen prior to the formation of the zygote
postzygotic barriers
reproductive barriers that isolate gene pools that happen after the formation of a zygote
5 prezygotic barriers
habitat isolation
behavioral isolation
temporal isolation
mechanical isolation
gametic isolation
habitat isolation
2 species live in different habitats and do not encounter each other
2 species of parasites live on diff hosts and never mate
behavioral isolation
special behavior unique
probably the important reproductive barrier with closely related species
fireflies of diff species have special patterns of blinking for mating
temporal isolation
2 species mate during different times of the day, diff seasons, or diff years
orchid flowers open in the morning and wither that evening allowing pollination occur only once the entire year
mechanical isolation
2 closely related species try to mate, but it is anatomically impossible
lock and key fit between bird species
gametic isolation
gametes may meet, but no zygote is formed
fish release eggs water next to the eggs of other species, and the sperm recognizes the correct eggs by specific molecules (proteins) on the coats of the eggs allowing for fertilization
3 postzygotic barriers
reduced hybrid viability
reduced hybrid fertility
hybrid breakdown
reduced hybrid viability
zygote has formed but is genetically incompatible between 2 species
abort, incomplete development, or be a weak offspring
reduced hybrid fertility
the hybrid offspring is healthy, but sterile due to the failure of meiosis to produce normal gametes if the chromosome number and structure different from the 2 parental series
donkey + horse = mule
hybrid breakdown
first generation hybrids are healthy and fertile, but when they mate with one another or with either parental species, the next generation is weak or sterile
what does the biological species concept not work for?
extinct life forms - the fossils must be grouped according to morphology
asexual organisms who don’t interbreed, but essentially make clones
sometimes it is too rigid - coyotes breed with dogs and produce fertile hybrid offspring but still are separate species
what does the biological species concept emphasize?
reproductive isolation of a species interbreeding with each other and not other species
5 alternative species concept
morphological species concept
recognition species concept
cohesion/pluralistic species concept
ecological species concept
evolutionary species concept
morphological species concept
separates species based on physical features
recognition species concept
emphasizes mating adaptations that enable a species to “recognize” mates
behavioral, morphological, or molecular
cohesion/pluralistic species concept
combining several of the species concepts together
ecological species concept
emphasizes where species live and what they do = their niche, the role the species plays in the environment
evolutionary species concept
emphasizes evolutionary lineage
2 ways to bring about speciation
allopatric speciation
sympatric speciation
when does allopatric speciation come about?
when a geographical barrier physically isolates a single population and blocks gene flow
then new populations undergo microevolution that may eventually lead to macroevolution– more likely that a small population will change substantially enough to become a new species
where does allopatric geographical location of a small population usually occur?
peripheral isolated population - boundary of a parent population’s range
what is the characteristic of the peripheral isolate’s genes? what happens if it is a small population?
differ from the parental population to begin with and if it is small population, the founder effect may result
what will happen until the peripheral isolate becomes a large population?
the gene pool will change a lot and at random due to mutations and sexual recombination
some alleles might become “fixed” (homozygous)
then evolution may occur by natural selection, especially is the environment is somewhat different, turning the peripheral isolate into a new species
what are living laboratories for speciation? why?
islands
they allow for adaptive/explosive radiation - the evolution of many diversely adapted species from a common ancestor
what is sympatric speciation?
occurs due to intrinsic factors such as chromosomal changes (in plants) and nonrandom mating(in animals) that alter gene flow
when populations coexist in the same idea, but are reproductively isolated
how can a new species be generated through a genetic change?
if a genetic change results in a mutant that cannot breed with the parent population
polyploidy
many plant species today resulted due to this having an extra set of chromosomes
autoploidy
polyploidy that came from a single species
alloploidy
extra set of chromosomes comes from another species
usually sterile and reproduce asexually
but are vigorous as they have combined the best qualities of their two parents
most commercial plants today are?
polyploids - oats, cotton, potatoes, tobacco, and wheat
how are polyploids with special qualities created?
done with the aid of radiation/chemicals
how can sympatric speciation occur in animals?
when animals of the same species living in the same area become reproductively isolated from the parent population as genetic factors cause them to become fixed on resources not used by the parent population
what happens when 2 closely related species that have been allopatric for some time come back into contact?
may be able to interbreed meaning speciation hasnt occurred
or
evolutionary divergence have led to 2 separate species that cannot interbreed
or
hybrid zone
what is a hybrid zone?
a region where 2 related populations that diverged after being allosterically separated come back together and interbreed only where their ranges overlap
ways reproductive isolation/species can occur
changing of many gene loci in a population - Darwin
changing of only a few loci in a population
what are scientists believing know contrary to Darwin’s beliefs?
gradual speciation alone does not bring about new species, it is now believed that some speciation occurred more rapidly
what is microevolution?
the idea that many small allele changes lead to big changed over a long span of time
what do we not find in fossils concerning gradualism?
rarely find gradual intermediates of fossil forms
instead we find new species appearing suddenly in layers of rocks and then disappearing as quickly as they appeared
punctuated equilibrium
species diverge in spurts of relatively rapid change then change a little even as they give rise to additional species
how quickly are these quick spurts thought to bring about change?
a few 100 or a few 1000 generations that can take thousands of year, short considering a successful species exists for a few million years
what is the equilibrium component of punctuated equilibrium?
the species stays the same for so long if the environment does not change
what is the punctuated component of punctuated equilibrium?
it is punctuated by episodes by speciation
what do gradualists think of equilibrium?
it is an illusion and that changes occur if not at the macro level than at the micro level
from what does the fossil record show that birds evolved from?
earthbound dinosaurs
what happened to the function of existing structures?
there was a refinement of existing structures for a new purpose
exaptation
refers to a structure that evolved in one context and became co-opted for another function
how can slight genetic divergence lead to major structural changed?
developmental biology and understanding allometric growth
allometric growth
other measure growth
a difference in relative rated of growth of different parts of the body help to shape an organism
paedomorphosis
retain juvenile features as am adult
axolotl keeps its gills
what does an evolutionary trend not mean?
does not mean it is goal orientated
what are species evolving a result of?
not choosing, but a result of genetic changes and the environmental response
the lineage showing a trend toward a larger body is due to what?
due to chance alone
what does the fossil record show in terms of emerging species?
fossils are not in a straight line but branches into many species
