evolution Flashcards
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🩶 Evolution – The process by which modern organisms have descended from ancient organisms.
🩶 Fitness – The ability to survive and reproduce in an environment.
🩶 Adaptation – Inherited characteristics that increase an organism’s chance of survival.
🩶 Gene Pool – The combined genetic makeup of all members of a population.
🩶 Genetic Drift – Random changes in allele frequencies in small populations.
🩶 Gene Flow – The transport of genes through migration.
🟩 Darwin’s Observations
Noticed that plants and animals were well-suited for their environments.
Found fossils that resembled living organisms but also ones he had never seen before.
Studied the Galápagos Islands, where close islands had different climates and species.
🟩 Hutton & Lyell’s Contributions
Hutton: Earth is millions of years old, based on slow geological changes.
Lyell: Earth changes over time → Darwin questioned if life could change as well.
🟩 Lamarck’s Theories (Flawed but Pioneering)
Tendency Towards Perfection – Organisms try to become “perfect.”
Use & Disuse – Organs used frequently grow stronger; unused ones shrink.
Inheritance of Acquired Traits – Believed traits changed in life could be passed to offspring.
🟩 Evidence for Evolution
Fossil Record – Shows gradual changes over millions of years.
Geographic Distribution – Similar species evolve in different locations.
Homologous Structures – Same structure, different function (e.g., human arm & whale flipper).
Embryology – Similar embryo development suggests common ancestry.
🟩 Natural Selection
Struggle for existence: Organisms compete for resources.
Survival of the fittest: Those best adapted survive and pass on traits.
Descent with Modification: Over generations, organisms evolve and diversify.
Common Descent: All life shares a common ancestor (LUCA).
🟩 Natural Selection on Traits
Directional Selection – One extreme trait is favored.
Stabilizing Selection – The middle trait is favored.
Disruptive Selection – Both extremes are favored; middle is selected against.
🟩 Hardy-Weinberg Principle (Genetic Equilibrium)
A population remains genetically stable if:
No natural selection
Random mating
No migration
No significant mutations
