selection n evolution

• Phenotype is the characteristics of an organism resulting from the interaction of its genes with the environment it lives in
• Types of variation:

  • Continuous variation: variation within a range, includes mass and height
  • Discontinuous variation: can only take particular values, such as gender or shoe size
• Variation in genotype affects variation in phenotype:

  • Monogenic characteristics show discontinuous variation
  • Polygenic inheritance involves several genes at different loci, leading to continuous variation
• Examples of characteristics influenced by both genotype and environment:

  • Height: a polygenic characteristic affected by poor nutrition
  • Genetic predisposition to lung cancer due to proto-oncogenes and smoking
  • Animal hair color, like Siamese cat fur color, determined by genotype and environment
• The student's T-test compares the mean values of 2 data sets using a specific formula
• Natural selection is the process where fitter individuals better adapted to the environment survive and pass on advantageous genes to future generations
• Evolution is the change in allele frequency in a gene pool over time due to natural selection
• Factors affecting evolution:

  • Genetic drift: small change in allele frequency, amplified in small isolated groups
  • Genetic bottleneck: rapid reduction in population size affecting genetic variation
  • Founder effect: decrease in genetic diversity from a small number of ancestors
• Speciation is the process where new species arise after a population becomes separated and cannot interbreed
• Antibiotic resistance is an example of natural selection where bacteria mutate to resist antibiotics
• The Hardy-Weinberg Equation estimates allele frequency in a population and detects changes over time
• Artificial selection is the process where humans create selection pressures to breed desired characteristics
• Examples of crop improvement by selective breeding:

  • Disease resistance in wheat and rice
  • Incorporation of mutant alleles for gibberellin synthesis into dwarf varieties
  • Inbreeding and hybridization to produce vigorous maize varieties
• Reasons for species extinction:

  • Killing by humans
  • Competition for food, space, and mates
  • Habitat loss and climate change