BIO2 Basic Mechanism

• Natural selection is the process through which populations of living organisms adapt and change, proposed by Charles Darwin and Alfred Russell Wallace in the mid-nineteenth century
• Darwin's principle of natural selection is governed by three principles:

  • Characteristics of organisms are inherited
  • More offspring are produced than can survive, leading to competition for limited resources
  • Offspring vary in characteristics, and those with inherited traits best suited for competition will survive and reproduce
• Darwin's concept of natural selection leads to a change in populations over generations, known as "descent with modification," presented in his book "On the Origin of Species" published in 1859
• Mutation is a change in the DNA sequence of a gene, a source of new alleles in a population, and can result in phenotypic changes that may be beneficial, harmful, or neutral
• Genetic drift occurs due to random sampling of alleles in offspring from the parent generation, influenced by chance events like mortality, mating, and fertilization, and can be magnified by natural or human-caused events
• Gene flow involves the flow of alleles in and out of a population due to migration of individuals or gametes, contributing to genetic diversity
• Recombination occurs during meiosis when chromosomes exchange genes, leading to the formation of unique gametes and increased genetic diversity between generations
• Natural selection is the process through which populations of living organisms adapt and change, proposed by Charles Darwin and Alfred Russell Wallace in the mid-nineteenth century
• Darwin and Wallace reasoned that offspring with inherited characteristics allowing them to best compete for limited resources will survive and have more offspring
• Darwin's "On the Origin of Species" presented the principles of natural selection in 1859
• Adaptation is a "match" of the organism to the environment, occurring when a change in genetic variation increases or maintains the match of the population with its environment
• Mutation is a change in the DNA sequence of a gene, a source of new alleles in the population
• Mutation can result in reduced fitness, beneficial effects on fitness, or neutral mutations with no effect on fitness
• Harmful mutations are removed from populations by selection, while beneficial mutations spread through populations
• Genetic drift occurs because the alleles in an offspring generation are a random sample of the alleles in the parent generation
• Genetic drift can be magnified by events like disasters or population division, leading to the bottleneck effect or the founder effect
• Gene flow results from the migration of individuals or gametes, leading to the flow of alleles in and out of the population
• Recombination occurs during meiosis when chromosomes exchange genes, promoting genetic diversity between generations