Evolution

  • Created by: elshuntt
  • Created on: 09-04-18 10:55
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  • Evolution
    • Evidence for evolution
      • Theory of evolution
        • Theory - a set of idea to explain why something is true (different to a hypothesis)
      • Types of evidence for evolution
        • Fossils
        • Distribution of species
        • Ring species
        • Body Plans
          • Homeobox & Hox Genes
        • Molecular Biology
          • Genome
            • Evolution - we've all descended from a common ancestor
            • The more recently separated the closer the species and releatedness
              • therefore their base sequences are more similar
          • Proteins
        • Homo-logy of Structures
          • similarities in bone structure
    • Genetic Diversity and Adaptation
      • Genetic Diveristy
        • The number of different alleles of a gene in a population
        • Natural Selection
          • Individuals of a population that are best suited to their environment survive and reproduce more, therefore the beneficial alleles are more likely to be passed on to the next generation.
          • Results in species being better adapted to their environment
      • changes in allele frequency over time
        • A variation of alleles exist in a population resulting in mutations
          • Selection for individuals with beneficial allele
            • This leads to differential reproductive success
              • Changes allele frequency over a long period of time.
      • Types of adaptations
        • anatomical
        • physiological
        • behavioural
      • Selection Pressures
        • Directional Selection
          • Usually a change in environmental conditions
          • Individuals with an extreme type of characteristic are more likely to survive and reproduce
          • With the presence of diases the organisms with an allele for antibiotic resistant will increase in offspring and antibiotic resistance will increase
        • Stabilising Selection
          • Individuals with characteristics of either extreme are less likely to survive and reproduce
          • e.g. human birth weight
            • Very heavy babies are more likely to die due to complications
            • Very light babies are more likely to die due to high surface area to volume ratio = cold
            • Babies in the middle range are more likely to survive, thus the population remains stable.
    • changes in allele frequency over time
      • A variation of alleles exist in a population resulting in mutations
        • Selection for individuals with beneficial allele
          • This leads to differential reproductive success
            • Changes allele frequency over a long period of time.
    • Varation
      • Intraspecific
        • Individuals of the same species have the same genes but different alleles (variation in their phenotypes)
      • Interspecific
        • Individuals of different species have different genes and live in different environments (variation in their phenotypes)
      • Continuous
        • variation is smooth (non-discrete)
        • Represented in a line graph
      • Discontinuous
        • Individuals fall into distinct groups with no intermediates
        • controlled by a single gene with a few alleles
        • represented on a bar chart e.g. blood group
      • Genetic Causes
        • Mutation
        • Meiosis (crossing over or random assortment)
        • Random fertilisation (e.g. blood group)
        • Inherited factors - genetic variations resulting in evolution
        • BOTH
          • Most variation is a result of both environemtal and gentic variation
            • e.g. height
              • GENETIC: tall parents tend to have tall children
              • Childhood mutation
      • Environmental Causes
        • Environmental changes that change phenotype
        • Can change over a lifetime
          • e.g. accent
        • BOTH
          • Most variation is a result of both environemtal and gentic variation
            • e.g. height
              • GENETIC: tall parents tend to have tall children
              • Childhood mutation
    • Convergant Evolution
      • organism that are not closely released can independently evolve very similar anatomy and behaviour because they become adapted to similar niches/habitats
    • Evolution of Resistance
      • Insects have evolved resistance to pesticides and herbicides
      • Bacteria has evolved resistance to antibiotics
      • Antibiotics and pesticides form a strong directional selection pressure
        • only individuals with rare mutations will survive and reproduce - passing on resistant alleles
        • resistant alleles will increase in frequency so a high proprtion of organisms become resistant
      • Consequences
        • Crops are ruined; harder to control/maintain; spread of disease (malaria)
        • Resistant infection - become life threatening

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