Evolution: The Theories and the Evidences

A set of practice flashcards covering key topics from the Evolution lecture notes.

What is a scientific theory?

A body of thoroughly tested explanations for a set of observations in the natural world; the best, evidence-backed explanation, supported by rigorous testing.

What is evolution?

A change over time in the heritable characteristics of biological populations.

What is Lamarckism (inheritance of acquired traits)?

The idea that traits acquired during an organism's lifetime are passed to offspring; now rejected as a mechanism of evolution.

What is Darwinism and natural selection?

Evolution via heritable variation and differential survival and reproduction; illustrated by the giraffe neck example.

Name the five Darwinian theories mentioned.

Perpetual Change; Common Descent; Multiplication of Species; Gradualism; Natural Selection.

Perpetual Change

The living world is always changing; the fossil record shows evolutionary change over time; scientifically accepted as a fact.

Common Descent

All forms of life descended from a common ancestor through branching lineages; recent common ancestry yields more similar features.

Multiplication of Species

Speciation occurs via the splitting and transformation of older species; populations become reproductively distinct; gene flow can hinder speciation.

Gradualism

Large differences originate from the accumulation of many small genetic changes over very long time periods.

Natural Selection — Overproduction

Organisms produce many offspring, but not all survive to adulthood.

Natural Selection — Variation

Populations exhibit heritable variations among individuals.

Natural Selection — Competition

Limited resources lead to a struggle for existence among individuals.

Natural Selection — Selection

Variants better adapted to the environment are more likely to survive and reproduce.

Natural Selection — Adaptation

Accumulation of favorable traits over generations can lead to new adaptations and, eventually, new species.

Embryological development as evidence

Embryos show features of evolutionary history; some structures disappear before adulthood (tail, gill slits, hindlimb buds in some lineages).

Homologous structures

Similar structures derived from a common ancestor (e.g., forelimbs in mammals).

Analogous structures

Structures with similar function but different evolutionary origins; developed independently due to similar pressures.

Vestigial structures

Remnants of ancestral structures with reduced or lost function (e.g., coccyx; vestigial hip bones in snakes).

The fossil record

Physical evidence of evolutionary change over time; reveals appearance, time, diet, and environment; often incomplete.

DNA comparisons

Relatedness reflected by DNA sequence similarity; humans share about 99% of DNA with chimpanzees, indicating a common ancestor.

Biogeography

Study of species distribution and the geographical factors (continents, islands) that shape evolutionary patterns; isolation can drive speciation.

Microevolution vs Macroevolution

Microevolution = small changes within a species; Macroevolution = large-scale changes above species level (genera, families, etc.).

Peppered Moths case

The Peppered Moth illustrates natural selection in response to environmental change: pollution darkened trees, increasing dark morphs and selective camouflage.

Great Divide case (squirrels vs birds)

Geographic isolation (Colorado River) led to speciation in Abert’s vs Kaibab squirrels; birds retained gene flow and did not speciates due to flight.