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13_Lecture_Presentation

Introduction to Evolutionary Biology

  • Historical Context of Malaria

    • In the 1960s, WHO aimed to eradicate malaria through DDT spraying.
    • Mosquito populations developed resistance to DDT, complicating eradication efforts.
    • Malaria remains a significant health issue, causing over 1 million deaths annually.
  • Evolution of Parasite Resistance

    • Chloroquine, once a miracle drug for malaria, became ineffective due to parasite resistance.
    • Understanding evolution is crucial across biology, from molecular life to ecosystems.

Darwin's Theory of Evolution

  • Darwin's Influence

    • Charles Darwin, in "On the Origin of Species by Means of Natural Selection," revolutionized biology.
    • His theory contrasted the view of a young, unchanging Earth populated by static species.
  • Concept of Descent with Modification

    • All species are linked through common ancestry.
    • Adaptations arise over time in response to changing environments.
  • Darwin's Theory as a Scientific Theory

    • A theory is a comprehensive explanation supported by substantial evidence and capable of generating hypotheses.

Evidence for Evolution

  • Fossil Record

    • Fossils serve as imprints/remains of past organisms, highlighting species differences and showing extinction.
    • The fossil record illustrates the evolutionary sequence of organisms over time.
  • Transitional Fossils

    • Transitional fossils link extinct species with current ones (e.g., whales and their ancestors).
    • Discoveries like Pakicetus and Rodhocetus strengthened understanding of whale evolution.
  • Homology

    • Homologous structures reveal evolutionary relationships among related species.
    • Vestigial structures indicate remnants of significant features in ancestors.

Mechanisms of Evolution

  • Natural Selection

    • Natural selection explains how traits favorable for survival and reproduction increase in frequency.
    • Observational evidence of natural selection has been recorded extensively in various species (e.g., pesticide resistance).
  • Genetic Variability and Evolution

    • Mutation serves as the source of genetic variation.
    • Sexual reproduction provides varied combinations of alleles.
  • Evolutionary Population Dynamics

    • A population is a group of individuals that interbreed. Changes within these populations can lead to evolution.
  • Hardy-Weinberg Principle

    • The Hardy-Weinberg equilibrium asserts that allele frequencies remain constant under specific conditions (large population, random mating, etc.).
    • This principle can be tested to determine if evolutionary changes are occurring.

Microevolution and Selection

  • Causes of Microevolution

    • Major factors include natural selection, genetic drift, and gene flow.
    • The bottleneck effect reduces diversity due to population shrinkage.
    • The founder effect occurs when a small group colonizes a new area, leading to genetic drift.
  • Natural Selection Types

    • Three selection types affect phenotypes: stabilizing (favoring average traits), directional (favoring one extreme), and disruptive (favoring both extremes).
  • Sexual Selection

    • This form of natural selection enhances traits that attract mates, influencing sexual dimorphism.

Public Health and Evolution

  • Antibiotic Resistance

    • Similar to pesticide resistance, antibiotics select for resistant bacteria, creating public health challenges.
    • Understanding these dynamics is critical in addressing drug resistant infections in society.
  • Genetic Variation Preservation

    • Mechanisms like diploidy maintain variation in populations.
    • Heterozygote advantage can reinforce genetic diversity.