Evolution 1 Flashcards
Allopathic speciation
Population becomes separated by a geographic barrier and cannot mate
Genetic drift
A variation in the frequency of different genotypes in a population (AA, Aa, aa)
Convergent evolution
When 2 unrelated species have similar traits exposed to similar environments and do not have a common ancestor
Sympatric speciation
New species formed without geographic barriers (mostly plants)
Prezygotic barriers
Prevents fertilization
Postzygotic barriers
Two species form an unfertile hybrid
Bottleneck effect
When a populations size and genetic variation is reduced for one or more generations due to natural causes or human intervention
Divergent evolution
Results in closely related species with different behaviors
Examples of allopatric speciation
An fish population was split in two by the formation of the Isthmus of Panama
When Pangea split, multiple species were separated
Examples of genetic drift
2 pink monkeys in the world (1 male and 1 female). Female monkey dies ensuring no more pure bred pink monkeys left
Freckled flower exchanges genetic material with an unfreckled flower. After a few seasons there are no freckled flowers left in the population.
Examples of convergent evolution
Sugar gliders and flying squirrels both have rodent bodies and can glide from tree to tree. They are from different continents
Seals and penguins both have flippers. Seal is a mammal, and the penguin is a bird
Examples of sympatric speciation
Apple maggot flies: gene flow reduced between flies that feed on different food varieties, even though they both live in the same geographic region
Orca forms in the NE Pacific and transient orcas inhabit the same waters but do not interbreed
Examples of prezygotic barriers
1) habitat isolation: live in the same area but different habitats (water snakes and land snakes)
2) behavioral isolation: two allopatric species do not mate because of differences in courtship behavior (male fireflies of a variety of species signal their females by flashing their lights in specific patterns)
3) mechanical isolation: when different species are isolated by their mechanics (flowering plants that don’t have the correct shape for a pollinator will not receive a pollen transfer - can’t fertilize)
Examples of postzygotic barriers
Hybrid inviability : a zygote is formed, but the embryo dies in early development (embryos of sheep and goats die before birth)
Hybrid sterility: a hybrid is developed, but is unable to produce due to the meiotic problems (horse and donkey = hinney or mule
Hybrid breakdown: successive generations of hybrids suffer lowered fertility, eventually dies out
