Study Notes for BIOL 101 Unit 9: Evolution

BIOL 101 Unit 9: Evolution
Definition of Evolution

  • Change in the genetic makeup of populations over time, particularly in the frequencies of alleles.

    • Recognized as a fact, supported by observations:

    • Mutations cause changes in phenotypes.

    • Mutation rates are measurable, showing changes in populations.

    • Observable evolution in fast-reproducing species like viruses (e.g., influenza, HIV) and bacteria over short periods.

    • Example: Development of antibiotic resistance and new bacterial strains.

    • Fossil record shows historical changes in plants and animals.

Evolutionary Theory

  • The actual evolution process is accepted; the theory explains how it happens:

    • Investigates factors affecting evolutionary changes (e.g., natural selection, genetic drift).

    • Explores how humans and other species evolved from ancient ancestors.

    • Examines why some species thrive and others go extinct.

    • Discusses applications of this knowledge in conservation.

Charles Darwin

  • Known as The Father of Evolution.

    • Initially studied medicine, then theology.

    • Served as a naturalist on the HMS Beagle from 1831-36:

    • Collected many plant and animal specimens.

Voyage of the HMS Beagle

  • Included key locations:

    • Galápagos Islands near Ecuador.

    • Various regions including North America, South America, Africa, Europe, and Asia.

Darwin’s Observations

  • Noted unique species on the Galápagos Islands that were similar to mainland species:

    • Hypothesized these species came from the mainland and evolved differently on each island.

    • Example: Finches with various beak shapes adapted to different food sources.

Unique Adaptations in Galápagos Animals

  • Species appeared well-suited to island environments, unlike mainland relatives.

    • Example: Marine iguanas that can feed underwater.

Fossil Discoveries

  • Discovered fossils resembling modern animals but much larger or different:

    • Example: Fossils of Glyptodonts looked like larger versions of Armadillos.

Developing the Theory of Evolution

  • Darwin formed a theory of evolutionary change (natural selection) after his voyage:

    • Changes in species happen through natural selection — where individuals with advantageous traits survive and reproduce more.

    • Those with superior traits pass them on, making those traits more common over time.

    • The environment determines which traits are adaptive (helpful).

On The Origin of Species

  • Darwin's important book, published in 1859:

    • Title: On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life.

    • Explained natural selection and evolutionary biology.

Influential Scientists

  • Charles Lyell:

    • Geologist who proposed the Earth is much older than the traditional 6,0006,000 years.

    • This idea provided enough time for gradual evolution to occur.

  • Thomas Malthus:

    • Observed that human populations grow faster than resources, leading to competition.

    • Darwin applied this idea to all species, noting that more offspring are produced than can survive, causing competition.

Artificial Selection

  • Darwin recognized that humans can select specific traits through selective breeding:

    • Example: Selecting traits in pigeons to create different breeds.

Genetic Variation and Evolution

  • Genetic differences are essential for evolution:

    • Offspring differ from each other and parents due to sexual reproduction and meiosis.

    • Helpful traits passed through generations lead to populations becoming better adapted.

Gene Pool

  • The total collection of all genes (alleles) within a population.

    • Each individual typically carries 22 alleles for every gene.

Evolution and Genetic Diversity

  • More diversity means a wider range of traits for selection to act on.

  • Populations with more diversity can adapt more easily to environmental changes.

Mechanisms of Evolutionary Change

  • Various mechanisms change the frequencies of alleles over generations:

    • Mutations

    • Natural selection

    • Gene flow

    • Genetic drift

    • Sexual selection

Mutations

  • Alterations in the DNA sequence:

    • Types of mutations and their impact:

    • Neutral mutations: No effect on survival (e.g., free vs. attached earlobes).

    • Harmful mutations: Bad for survival (e.g., color blindness).

    • Helpful mutations: Provide advantages for survival (e.g., opposable thumbs).

Natural Selection

  • In different environments, traits become common based on how helpful they are:

    • Adaptive traits increase survival and reproduction, becoming more frequent in populations.

    • Environmental factors include:

    • Climate

    • Surrounding environment (e.g., land vs. water)

    • Species interactions (e.g., competition, predators, food).

Examples of Natural Selection

  • Evolutionary Adaptation:

    • Peppered moth turned darker to blend with polluted tree trunks during the Industrial Revolution.

    • Antibiotic resistance emerged in bacteria, allowing resistant strains to survive and multiply when exposed to antibiotics.

Gene Flow

  • Movement of alleles between populations through:

    • Migration of individuals

    • Migration of gametes (e.g., pollen)

    • This introduces/removes alleles, changing frequencies and potentially increasing diversity.

Genetic Drift

  • Random changes in allele frequencies, especially strong in small populations:

    • Population bottleneck: A dramatic reduction in population size, leading to a random loss of genetic diversity.

    • Example: Survivors of a natural disaster may not represent the original population's full genetic range.

    • Founder Effect: A small group separates to start a new population, carrying only a limited subset of the original genes.

Sexual Selection

  • A type of natural selection focused on mate choice:

    • Competing Traits: Traits that help males compete for mates increase reproductive success.

    • Attractiveness Traits: Traits that make individuals (often males) attractive to mates can increase mating opportunities, even if they don't help survival (e.g., vibrant bird plumage).

Female Mate Choice

  • Factors influencing female preferences for mates include:

    • Physical attractiveness

    • Male resources (e.g., territory, food)

    • Behavioral traits (e.g., songs)

Summary of Sexual Selection

  • Sexual selection favors traits that improve mating success, even if they sometimes reduce an individual's survival.

    • These traits often signal genetic quality, fitness, or resources.