Origins & Deep Time
This scientific field reconstructs evolutionary relationships among species.
What is phylogeny?
Darwin’s core mechanism of evolution, where beneficial traits increase in frequency.
What is natural selection?
The raw material of evolution—changes to DNA sequences.
What are mutations?
The formation of new species.
What is speciation?
This scientist proposed natural selection as the main mechanism of evolution.
Who is Charles Darwin?
The earliest evidence of life comes from these structures formed by microbial mats over 3 billion years ago.
What are stromatolites?
This random process is especially strong in small populations and can lead to allele loss.
What is genetic drift?
These structures are traits that once had a function but no longer do. An example of this is the coccyx bone in humans, also called a tailbone.
What are vestigial structures?
This geographic model of speciation involves a physical barrier separating populations.
What is allopatric speciation?
This key requirement for evolution states that individuals in a population must differ from one another.
What is variation?
This event around 540 million years ago saw a rapid diversification of animal body plans.
What is the Cambrian explosion?
When individuals immigrate or emigrate, they alter allele frequencies through this process.
What is gene flow?
This phenomenon occurs when a trait that originally evolved for one function becomes co-opted for another.
What is exaptation?
This occurs when species evolve together in response to each other’s adaptations (e.g., host and parasite).
What is coevolution?
This principle in evolutionary biology states that all species share common ancestry and diverged over time.
What is descent with modification?
This dating method uses the predictable decay of radioactive isotopes to determine the age of rocks.
What is radiometric dating?
This type of selection favors extreme phenotypes at both ends of a distribution.
What is disruptive selection?
This evolutionary concept states that species must constantly evolve just to maintain their relative fitness.
What is the Red Queen hypothesis?
These traits evolve not for survival, but for attracting mates—sometimes at a survival cost.
What are sexually selected traits?
The term for a feature inherited from an ancestor, even if its appearance has changed over time.
What is a homologous structure?
This method estimates the time since two species diverged by comparing genetic differences that accumulate at roughly steady rates.
What is a molecular clock?
A sharp reduction in the size of a population due to environmental events that reduce the variation in the gene pool of a population.
What is bottleneck effect?
This concept describes when one gene affects multiple traits, sometimes limiting adaptive evolution.
What is pleiotropy?
This pattern of evolution describes long periods of little change interrupted by brief bursts of rapid diversification.
What is punctuated equilibrium?
This evolutionary process explains why animals sometimes help relatives at a personal cost, because doing so increases the spread of shared genes.
What is kin selection?