Natural Selection Developed by Charles Darwin in 1859 Mechanism by which better adapted organisms survive to produce a greater number of viable offspring Improve chances of survival Variation Individuals in a population vary in phenotype which also means their genotype Some variations are better suited for survival and are inherited Overproduction Populations tend to produce more offspring than are needed

Neo-Darwinism Refined version Darwin’s theory Combines Mendel’s genetics Evolution is driven by chance 2 ways Small scale mutations (single nucleotide polymorphisms) Large scale mutations (recombination) Creates new DNA by lucky accidents

Gene Pools Total genetic information (alleles) in the gametes of all individuals in any given population

Population Group of organism’s of one species that interbreed and live in the same place at the same time

Factors that Affect Gene Pools Mutation Emigration Geographical Barriers Non-Random Mating Genetic Drift Bottleneck effect, founder effect Gene Migration Speciation Selection Pressure Adaptive Radiation

Factors Contribute to Fitness of Individual Measure of how well suited an organism is to survive in its habitat and its ability to maximize the numbers of offspring surviving to reproductive age How successful an organism is at passing on its genes Natural selection tends to lean towards individuals who have specific traits that favour them in the environment

Allele Frequency (Gene Frequency) Proportion of a particular allele (variant of a gene) among all allele copies in a specific gene pool Hardy-Weinberg principle is used to determine allele frequency: p² + 2pq + q² = 1 “p” and “q” represent frequency of alleles “p” added to “q” always equals one (100%)

Mutation Random occurrences which change the genome of the organism Increase genetic diversity Advantageous mutations are favoured by natural selection Disadvantageous mutations are phased out

Geographical Barriers Isolates the gene pool and prevents regular gene flow between populations

Non-Random Mating Members of gene pool seek out particular phenotypes increasing frequency of particular alleles Decreases genetic diversity Also known as selective breeding Humans breed livestock and plants for particular traits (favourable) Can lead to in-breeding depression caused by deleterious recessive alleles (cause abnormalities or death)

Genetic Drift Species of same population split into groups Geographical barriers do not allow members of same gene pool to reproduce with one another increasing genetic diversity Founder Effect New population is started by few members of original population Contains reduced genetic variation Non-random samples of genes Bottleneck Effect Population size is reduced for at least one generation Reduces genetic variation

Gene Migration Immigration Gene Flow Emigration Populations gain alleles from other gene pools Dependent on difference in allele frequencies between gene pools Gene Flow Members from one gene pool mate with members of another gene pool leading to alteration of allele frequencies Emigration Population loses alleles from gene pool

Speciation Genetic variation among population is so different that members can no longer reproduce with one another New species is formed

Selective Pressure Environmental factors reducing reproductive success among members of a population Contribute to evolutionary change or extinction through process of natural selection Include Competition, predation, disease, parasitism, land clearance, climate change, pollutants

Antibiotic Resistant Bacteria Microorganisms show resistance to an antimicrobial drug that was originally effective for treatment Conjugation Transfer of genetic material between bacterial cells Creates genetic diversity Antibiotic resistance

Adaptive Radiation Species from a common ancestor have successfully adapted to their environment via natural selection Less competition in population New ecological niches established (organisms function in environment) Darwin’s finches

Types of Natural Selection Occur with or without environmental change Effect a population Stabilizing Selection Constant environment Maintain status quo Directional Selection New variation arises in constant environment Disruptive Selection Changing environment Variations that result in better fitness in environment are favoured

Stabilizing Selection Favours the average individuals in a gene pool Selects against extreme phenotypes of gene pool Favours majority of population in gene pool Diversity is decreased Human birth weight Infants with average birth weight have increased chance of survival

Directional Selection Favours one extreme phenotype over another extreme phenotype Phenomena is observed in environments that have changed over time (climate change, food availability) Population bell curve shifts to left or right Fewer average individuals when compared to stabilizing selection Beak length of Galapagos finches Influenced by human interaction (hunting)

Disruptive Selection Average individual in a population is not favoured Extreme phenotypes are observed Lead to speciation (new species) Diversity increased Influence by human interaction (environmental pollution) London’s peppered moths

Sexual Selection Special case of natural selection An organism’s ability to successfully copulate with a mate Usually female chooses among males 2 ways Female choice Male competition

Female Choice Intersexual selection between sexes Females choose males based on specific characteristics or behaviours

Male Competition Intrasexual selection Males compete against other males for territory or mating rights with females Lead to intense battles

Evidence of Evolution Fossil record of change in earlier species DNA/protein homologies Geographic distribution of related species Recorded genetic changes in living organisms over many generations

DNA/Protein Homologies All living things on earth share the ability to create complex molecules out of carbon and a few other elements All plants and animals inherit their specific characteristics from a combination of genes Protein is made from DNA made up mostly of only 20 kinds of amino acids