02b - Variation and Adaptation

Variation

  • Variation = physiological, structural, or behavioural differences between individuals in a population

  • Exists naturally within most populations

  • Arises and changes due to mutations

  • Populations with little variation (inbreeding) may struggle to adapt

Types of Variation

  • Discontinuous Variation – Distinct categories

    • Can not be measured over a range, no in between features (e.g. blood type)

  • Continuous Variation – Range of differences 

    • No distinct categories, fall within a range of two extremes (e.g. height, skin color)

Mutations and Effects

  • Harmful mutations: cause death or struggle → genes removed from gene pool

  • Neutral mutations: no effect → genes persist in gene pool

  • Advantageous mutations: improve survival/reproduction → genes increase in gene pool

Adaptation

  • Adaptation = characteristic that helps an organism survive and reproduce in its environment

  • Context-dependent; what helps in one environment may not in another

  • Adaptations are inheritable

  • Not all variations become adaptations—favourable ones are selected by natural selection

Types of Adaptations

  1. Physiological – biochemical responses (e.g. hibernation lowers metabolism)

  2. Structural – anatomical features (e.g. camouflage, night vision)

  3. Behavioural – habits or actions (e.g. migration, cave-dwelling)

Selective Pressure

  • Selective pressure = external factors that affect survival or reproduction

  • Environment determines adaptations

  • Examples:

    • Climate change increasing average temperatures

    • Invasive species like Zebra Mussels colonizing the Great Lakes

Example: English Peppered Moth

  • Light and dark colour variations

  • 1848: 2% dark, 1898: 95% dark, 1990: 30% dark

  • Example of anthropogenic (human-caused) selective pressure due to pollution and environmental change

Mimicry

  • Structural adaptation where a harmless species resembles a harmful one

  • Example: Viceroy butterfly mimics Monarch butterfly

    • Monarchs are toxic to birds → birds avoid them

    • Viceroys with similar markings gain a selective advantage