Timelines of Change
What term describes slow, continuous evolutionary change over long periods of time?
Gradualism
What type of evidence includes preserved remains or traces of organisms from the past?
Fossil record
What is Biological Fitness?
an organism’s ability to survive and reproduce in its environment
Scenario:
In a grassland ecosystem, rabbits vary in fur color. Dark-fur rabbits are more visible to predators, while light-fur rabbits blend into the environment and survive to reproduce more often.
Question:
How will the fur color of the rabbit population likely change over several generations, and why?
The population will have more light-fur rabbits because that trait increases survival and reproduction through natural selection.
What term describes the formation of new species?
Speciation
What pattern of evolution involves long periods of little change followed by short bursts of rapid change?
Punctuated Equilibrium
Scenario:
The forelimbs of humans, whales, and bats have different functions, but their bone structures are arranged in a very similar way.
Question:
What type of evolutionary evidence does this represent, and what does it suggest about these organisms?
Homologous structures
What is the total collection of genes in a population
Gene Pool
What three conditions are necessary for natural selection to occur?
Variation, overproduction, and differential survival/reproduction
What type of isolation occurs when populations are separated by physical barriers?
Geographic isolation
What is the term for a long period in which a species shows little or no evolutionary change?
Stasis
What type of structures perform similar functions but evolved independently?
Analogous Structures
Scenario:
A population of beetles lives on a windy island. A storm randomly kills many beetles, leaving only a few survivors. The surviving population has a different allele frequency than before the storm.
Question:
Which evolutionary mechanism best explains the change in allele frequency, and why?
Genetic drift, because the change was random and not due to trait advantages.
Why are variations within a population important for natural selection?
They allow some individuals to survive and reproduce better than others
What is it called when populations can no longer mate and produce fertile offspring
Reproductive Isolation
Scenario:
Scientists studying a species of marine snail observe that the species remains mostly unchanged for millions of years. Suddenly, after a major change in ocean temperature, several new shell shapes appear in a relatively short period of time.
Question:
Which evolutionary pattern does this scenario best represent, and why?
Punctuated equilibrium, because long periods of little change are followed by short bursts of rapid evolution.
How does molecular evidence (like DNA or proteins) support evolution?
Similar DNA or protein sequences suggest common ancestry
What is gene flow?
The movement of alleles into or out of a population due to migration
What happens to advantageous traits over time in a population?
They increase in frequency
How can changes in allele frequencies lead to speciation?
Accumulated genetic differences prevent successful reproduction between populations
Why does the fossil record often support punctuated equilibrium rather than gradualism?
Fossils form infrequently due to quick changes in the environment, so rapid changes in the organisms appear sudden with long gaps showing little change
Species in similar environments evolve similar traits due to shared ancestry or environmental pressures
Biogeography
What is coevolution
when two species evolve in response to each other
Explain why natural selection acts on populations, not individuals.
Individuals do not evolve; populations change as allele frequencies shift over generations
How can behavioral isolation lead to speciation even when two populations live in the same geographic area?
Differences in mating behaviors or timing prevent interbreeding, leading to reproductive isolation and the formation of new species