Real-World Examples
Peppered moths
natural selection (directional)
What biologically defines a "species"?
interbreeding between organisms that results in viable, fertile offspring are of the same species
Natural selection is also called
survival of the fittest
Evolution affects ____________.
populations
These remains or imprints of once-living organisms provide direct evidence of evolution. The older ones are found here.
fossils; deeper in the ground
overhunting the American buffalo from millions down to hundreds
genetic drift (bottleneck effect/event)
When two populations become separated by a physical barrier like a river or mountain (geographic isolation).
Allopatric speciation
When individuals at one extreme of a trait have higher fitness, this type of selection occurs.
directional selection
Over many generations, traits that increase survival and reproduction become more common through this process.
natural selection
Structures that share similar anatomy but have different functions. What is an example of this?
Homologous (human arm and whale flipper)
Antibiotic resistance
natural selection (directional)
Give a real-world example of speciation occuring.
the Grand Canyon squirrels, Death Valley pupfish, Galapagos finches
When both extremes of a trait are favored, resulting in two distinct phenotypes, this type of selection occurs.
disruptive selection
Random changes in allele frequencies that have a greater effect in small populations describe this mechanism.
genetic drift
Structures that share similar functions but have different anatomy. What is an example of this?
Analogous (bird wing and butterfly wing)
polydactyly in the Amish or
Deafness in the residents of Martha's Vineyard, MA
(a small, isolated population of humans)
genetic drift (founder's effect)
All types of isolation OTHER than geographic cause this type of speciation.
Sympatric speciation
This type of natural selection favors the moderate/intermediate/average form of a trait.
stabilizing selection
When individuals move into or out of a population, introducing or removing alleles, this occurs.
gene flow
Evolutionary "leftovers" without useful functions in modern organisms (but they were once used)! Give one human AND one non-human example.
Vestigial
human - wisdom teeth, appendix, wrist tendon, tailbone
non-human - wings of flightless birds, whale pelvic bones, leg bones in snakes
observable changes in a population’s allele frequencies over time
microevolution
What are the four types of isolation that can cause speciation?
Geographic, Behavioral, Reproductive, and Temporal
Give three different examples that show how natural selection affects organisms.
Stabilizing - clutch size of birds (medium favored)
Disruptive - rock pocket mice (extremes favored)
Directional - antibiotic resistance (one extreme favored)
What are the two main types of genetic drift?
bottleneck effect and founder's effect
The idea that mitochondria and chloroplasts were once free-living bacteria that merged with and gave rise to eukaryotic cells.
Endosymbiotic Theory