Macroevolution Flashcards
Biological species concept
a population or group of population in nature whose individual members can interbreed to produce viable, fertile offspring that can also interbreed
example of biological species concept
Grey’s zebra (endangered) and plains zebra (widespread) are different species- can’t interbreed
speciation occurs when..
population become isolated over time
speciation
when some members of a sexually reproducing population change so much that they are no longer able to reproduce
speciation causes formation…
of new species from existing species
what’s the most common form of speciation?
allopatric speciation
allopatric speciation occurs when…
populations of a species are geographically isolated
Can no longer exchange genetic information
in allopatric speciation, over many generation the populations…
gradually become less and less alike
in allopatric speciation, eventually two populations evolve…
some sort of reproductive isolating mechanism
What is a form of allopatric speciation?
Adaptive radiation
example of allopatric speciation
the isthmus of Panama arose some 3 million years ago, populations of snapping shrimp have diverged into seperate species
Sympatric speciation occurs….
gradually or suddenly
In plants sympatric speciation occurs mostly because of…
chromosomal changes
ex. Polyploidy
How does sympatric speciation evolve?
new species evolves from within a large population
In animals sympatric speciation occurs because of…
non-random mating, ex, Squirrels mate at sunset and sunrise results in 2 new species
Ex. Diane Dodd maltose vs starch flies
where does sympatric speciation occur?
occurs in species in within the same geographical area
how does adaptive radiation occur?
When members of a single species occupy a variety of distinct niches within with different environmental conditions
what does adaptive radiation describe?
describes the rapid evolutionary diversification of a single ancestral line
example of adaptive radiation
beak types in finches of the Galapagos Islands
In adaptive radiation, members evolve…
different morphological features (adaptations) in response to the different selection pressures
What are pre-zygotic isolating mechanisms?
barriers that either impede mating between species or prevent fertilization
What are the 5 pre-zygotic isolating mechanisms
behaviour, habitat, temporal (timing) , mechanical, gametes
examples of behavior
bird songs, courtship rituals of elk, insect pheromones
certain groups of birds will only respond to species-specific mating calls
Behaviour
any special signals or behaviours that are species specific
prevent interbreeding with closely related species
Habitat
two species may live in the same general region but different habitats
rarely encounter each other
example of temporal (timing)
three tropical orchid species time lapse between weather stimulus and flowering is 8,9, and 10 days respectively
Temporal (timing)
two species may occupy the same habitat but mate or flower at different times of day, seasons or years
examples of habitats
common garter snake found near water whereas northwest garter snake found in open areas (like meadows)
another example of temporal
frogs will live same pond but breed during different seasons (spring vs summer)
Mechanical
closely related species may attempt to mate but fail to achieve fertilization between they are anatomically incompatible
example of mechanical
genitalia specificity in insects
certain breeds of dog are morphologically incapable of mating due to size
Gametes
egg and sperm meet but rarely fuse to form a zygote
example of gametes
sperm of one species cannot survive in the environment of the female reproductive tract of another species
what are post-zygotic isolating mechanisms?
barriers the prevent hybrid zygotes from developing into viable fertile individuals
what are the three post-zygotic isolating mechanisms?
hybrid inviability, hybrid sterility, hybrid breakdown
what is hybrid inviability?
embryo dies in early development before birth
genetic incompatibility prevents normal mitosis after fusion
example of hybrid inviability
sheep and goats
what is hybrid sterility?
hybrid offspring is sterile
meiosis fails to produce normal gametes in the hybrid because chromosomes of the tow different species differ in number of structure
example of hybrid sterility
mule offspring between female horse and male donkey n
examples of hybrid breakdown
hybrids between the cotton species Gossypium barbadense, G.hirsytum and G.tomentosu
The offspring of hybrid copepods have less potential for survival or reproduction
what is hybrid breakdown?
Hybrids can mate with each other but produce either weak or sterile offspring in the next generation
where does hybrid breakdown occur?
in plants
Divergent evolution
common ancestor
diverge to produce homologous structures
species appearance becomes more different over time
species are closely related (share genetic homology)
example of divergent evolution
pentadactyl limb structure (vertebrates)
convergent evolution
different ancestor
converge to produce analogous structures
species appearance becomes more similar over time
species are unrelated (genetically different)
2 models of speciation
phyletic gradualism
punctuated equilibrium
example of convergent evolution
wings in insects, birds and bats
what is phyletic gradualism?
speciation occurs uniformly
steady and gradual transformation of whole lineages
What is punctuated equilibrium?
species remain stable for long periods before undergoing abrupt and rapid changes (speciation)
example of phyletic gradualism
fossil record of horse shows many intermediate forms connecting ancestral to modern species
In punctuated equilibrium, speciation is seen as…
periodic process (big changes occur suddenly followed by long periods of no change)
punctuated equliibrium is supported by…
general lack of transitional fossils (such absences could be because fossilization conditions are rare)
