Mechanisms of Evolution
Variation + Selection =
What is Evolution?
Organisms that are best adapted to their environment survive and reproduce; organisms that lack suitable characteristics are selected against.
What is Natural Selection?
The relatively rapid evolution of a single species into a number of distinct but closely related species filling a variety of formerly empty ecological niches
What is adaptive radiation?
This process occurs when the evolutionary success of one species, like a flowering plant, is tied to another, like its pollinator.
What is coevolution?
Permanent random change in the genetic material of an organism
What are mutations?
The movement of alleles from one population to another
What is gene flow?
This type of selection favors the average phenotype and selects against both extremes (e.g., human birth weight).
What is stabilizing selection?
A population of squirrels is split in two when the Grand Canyon forms; over thousands of years, the two groups evolve different fur colors and mating calls, and can no longer mate when reunited
What is allopatric speciation (due to Geographic Barrier)?
This theory suggests that evolutionary change happens in small, steady steps over very long periods
What is gradualism?
Two species of frogs are able to produce a healthy "hybrid" offspring; however, when that hybrid grows up and tries to mate with other frogs, it is found to be completely sterile.
What is Hybrid Infertility (a Postzygotic Mechanism)?
This occurs when a few finches from the mainland start a new colony on an island, carrying only a small fraction of the original genetic diversity.
What is the founder effect?
This type of selection would occur if finches with medium-sized beaks were at a disadvantage, favoring only those with very small or very large beaks.
What is disruptive selection?
These two types of reproductive mechanisms prevent different species in the same area from interbreeding.
What are prezygotic and postzygotic mechanisms?
Sharks (fish) and dolphins (mammals) both evolved streamlined bodies and dorsal fins to navigate the ocean efficiently, despite coming from completely different evolutionary lineages.
What is Convergent Evolution?
a period of rapid evolution and species diversification
What is the Cambrian explosion
Directional selection, stabilizing selection, disruptive selection are all types of ...
What is natural selection?
If a drought only leaves large, hard seeds, finches with larger beaks survive and reproduce; this is an example of this specific "mode" of selection.
What is directional selection?
A horse and a donkey can mate to produce a mule; however, because the mule is sterile and cannot produce its own offspring, horses and donkeys remain separate according to this specific scientific definition.
What is the Biological Species Definition?
The kit fox lives in the desert and has large ears to dissipate heat, while the closely related Arctic fox has small ears to retain heat. Despite their common ancestor, they have become increasingly different.
What is Divergent Evolution?
This specific term refers to any trait—structural, behavioral, or physiological—that enhances an organism's fitness and chance of survival.
What is an adaptation?
After a 1780s hurricane wiped out all but 20 people on the Pingelap Atoll, the surviving population eventually rebounded, but today 10% of the island has complete colour blindness—a rare trait that was passed down by just one of the original survivors.
What is the genetic bottleneck effect?
The favouring of any trait that specifically enhances the mating success of an individual
What is sexual selection?
Two closely related species of fruit flies live in the same geographic area; however, one species mates only at sunrise while the other mates only at dusk, preventing them from ever interbreeding.
What is Temporal Isolation (Sympatric Speciation)?
A paleontologist finds that a species of trilobite remains completely unchanged in the fossil record for millions of years, but is suddenly replaced by a distinct descendant species in a geologically short period of time with no 'intermediate' fossils found
What is punctuated equilibrium?
A single ancestral species of wildflower gradually changes over time until the entire population has evolved into a new species, leaving no members of the original parent species behind.
What is Transformation (or Anagenesis)?