Evidence & Definitions
Define “evolution” in one sentence.
Change over time
Who was Charles Darwin and what basic idea is he famous for proposing?
Charles Darwin: Naturalist who proposed that species change over time by the process of natural selection.
What are embryos?
Embryos: Organisms in early development before birth or hatching.
What is an adaptation?
Adaptation: A heritable trait that increases an organism’s chances of survival and reproduction in its environment.
What is a fossil? Give one example.
Fossil: The preserved remains, impressions, or traces of ancient organisms (example: leaf imprint in rock, trilobite shell).
Which of the four main proofs of evolution is described as “preserved evidence or stony traces of an ancient living thing found within rock layers”?
Fossils
On which islands did Darwin make key observations about finches and adaptation?
Galápagos Islands
What is a vertebrate? Give an example.
Vertebrate: An animal that has a backbone/spinal column (example: fish, birds, mammals).
What is natural selection in one clear sentence?
Natural selection: The process by which individuals with favorable heritable traits produce more offspring, causing those traits to become more common in a population.
How do organisms typically become fossils?
Typical fossilization process: Rapid burial by sediment, mineralization/permineralization, and long-term preservation in rock layers.
What is a species? Give the simplest scientific definition.
Species: A group of similar organisms capable of interbreeding and producing fertile offspring.
Describe one important observation Darwin made about the birds he studied and how it supported his theory.
Darwin observed that finches on different islands had differing beak shapes adapted to food sources; this supported natural selection.
Define “homologous structures” and give two examples from different species.
Homologous structures: Body parts in different species that are similar because of shared ancestry (examples: human arm and whale flipper; bat wing and human hand bones).
Why are some organisms less likely to survive if they lack beneficial adaptations?
Organisms lacking beneficial adaptations are less likely to survive and reproduce; over time their traits decrease in frequency.
Why are there gaps in the fossil record? Provide two reasons.
Gaps in the fossil record: Fossilization is a rare event; many organisms (especially soft-bodied) do not fossilize well; geological processes (erosion, metamorphism) can destroy or conceal fossils; sampling bias and incomplete rock exposure also contribute.
Explain what “cell evidence” (or molecular/DNA evidence) tells scientists about relatedness between organisms.
Cell/DNA evidence: Similarities in DNA sequences, proteins, and cellular structures indicate common ancestry and allow scientists to measure relatedness.
Explain why Darwin’s voyage and observations alone were not enough; what additional evidence or reasoning made his ideas persuasive?
Darwin needed supporting evidence and a mechanism: accumulation of observations (variation, competition) plus later genetic and fossil evidence made his theory persuasive.
Explain how embryonic development across species can be evidence for common ancestry.
Embryonic development evidence: Early developmental stages (such as pharyngeal arches, tails, limb buds) are similar across related species, indicating conserved developmental pathways and shared ancestry.
Explain how variation, competition, and differential reproductive success combine to produce natural selection.
How natural selection works: Variation exists among individuals; limited resources cause competition; individuals with advantageous traits survive and reproduce more; allele frequencies shift across generations.
Which type of evidence (embryos, DNA, body structures, fossils) often provides the most direct record of past life and why?
Most direct record of past life: Fossils — they provide tangible, physical evidence of past organisms and their morphological changes through time. (Note: DNA provides powerful evidence for relatedness among living taxa, but fossils uniquely document extinct forms and morphological transitions.)
Differentiate between “ancestor” and “common ancestor” with a short example.
Ancestor vs. common ancestor: Ancestor — an earlier organism or population from which another descends. Common ancestor — a past population shared by two or more descendant species (example: humans and chimpanzees share a common ancestor).
Summarize how the phrase “survival of the fittest” relates to, but is not identical with, Darwin’s original concept of natural selection.
“Survival of the fittest” emphasizes differential reproductive success; while often attributed to Darwin, the exact phrase was coined by Herbert Spencer. It aligns with natural selection but can be misunderstood—“fittest” means best suited to an environment, not strongest.
Contrast homologous structures with analogous structures and explain why each arises.
Homologous vs. analogous structures: Homologous structures share common ancestry and similar underlying anatomy but may have different functions (e.g., human arm vs. whale flipper). Analogous structures have similar function but different evolutionary origins (e.g., bat wing vs. insect wing) and arise by convergent evolution.
Describe how genetic mutation and recombination contribute to evolution over many generations.
Role of mutation and recombination: Mutations introduce new genetic variants (alleles); sexual reproduction and recombination reshuffle alleles. These processes create the heritable variation upon which natural selection acts, driving evolution over many generations.
Explain how transitional fossils support the idea of gradual change, and give one well-known example.
Transitional fossils: Fossils that show intermediate traits between major groups support gradual change (example: Archaeopteryx shows both dinosaur and bird features; Tiktaalik shows fish and tetrapod features), demonstrating stepwise evolutionary changes.