Lesson 3: Mechanism

• Mutation


  A change in the DNA sequence of a gene, creating a new phenotype. Mutations are a great source of genetic variation.
• Mutations


  • May be beneficial, detrimental, or neutral to the organism's fitness
  • Mutations that occur in somatic cells are not inherited by offspring
  • Mutations that occur in sex cells (germ-line) can be inherited by offspring
• Gene flow


  The transfer of genes from one population to another due to the migration of individuals or gametes. This increases variability within the population.
• Genetic drift


  The change in allele frequencies in a population due to chance events, often called "sampling error" in selecting alleles for the next generation.

  
• Genetic drift


  • Has a greater impact in small populations
  • Examples: Bottleneck effect - large decline in population size leads to significant change in allele frequencies
  • Founder effect - a new population is established by a small number of individuals from a larger population, leading to reduced genetic variation

  
• Natural selection


  The process by which certain traits become either more or less common in a population based on their relative fitness.
• Artificial selection


  The process by which humans breed plants and animals to encourage the occurrence of particular traits.
• Recombination


  The process by which offspring receive a different combination of traits than their parents, due to the random assortment of chromosomes during meiosis.
• Evolution refers to the process of gradual change in a population over generations.
• Bottleneck effect


  Happens when there is a large decline in the number of surviving species in a population when events like natural disasters (earthquakes, floods, fires) occur. The allele frequency in the population is significantly different from the population prior to the event, and some alleles from the population may be reduced, if not entirely wiped out.

  
• Founder effect


  Occurs when a small group of individuals separates from a larger population and creates a new group. The alleles in the founding population may be present at different frequencies than in the original population, and some alleles may dominate the population or may be missing entirely.
• Genetic drift would happen more quickly on an island than on the mainland
• Natural selection


  Occurs when the allele/s makes individual more or less fit in the environment. If the allele reduces its fitness, the frequency of the allele is more likely to drop in the succeeding generations; however, if the allele favors the population to survive and reproduce, it will be passed on to the offspring and over a period of time, it can create populations that have adapted to succeed in specific environments
• Artificial selection


  Also called "selective breeding", occurs with the interference of humans. Humans select the desirable traits of the organisms to be mated, like in agricultural products or animals.
• Recombination


  Occurs during meiosis when chromosomes undergo the process of exchanging of genetic material. It is a source of new combinations of genes and responsible for producing genetic combinations which are sometimes not found in earlier generations. It promotes genetic diversity to the population, however, works with natural selection by creating genes relative to the need of the organisms with respect to the environment where the organism thrives.
• Mechanisms of evolution


  • Natural selection
  • Genetic drift
  • Gene flow
  • Mutation
  • Recombination
  • Artificial selection
• Invasive species are organisms that are not originally found in a certain place
• The Golden apple snail, locally known as Golden Kuhol, was originally introduced to increase the protein source of the Filipino diet, but is now a major pest hindering the promotion and adoption of direct-seeded rice