Genetics and Evolution Notes

Genotypes and Phenotypes

  • Genotype: An organism's collection of genes inherited from parents.
  • Phenotype: An organism's physical characteristics, influenced by both genetic and environmental factors.

Variation

  • Variation: Differences in phenotypes within a population, including physical, social, and academic traits.

Reasons for Variation

  • Genes: Inherited genes control characteristics (e.g., blood type, eye color, tongue rolling).
  • Environment: The environment significantly impacts phenotype (e.g., accent).
  • Genes and Environment: Most traits are influenced by both genes and environment (e.g., weight).

Variation Within and Between Species

  • Within Species: Individuals of the same species have similarities with less variation.
  • Between Species: Individuals of different species are very different with lots of variation (e.g., lion vs. human).

Mutation

  • Mutation: Random change in genetic material during replication.
    • May or may not affect the phenotype; can be silent.
    • Beneficial mutations can give an advantage and be passed on.

Evolution

  • Evolution: Change in allele frequencies in a population over time.
    • Leads to changes in phenotypes to suit the environment through natural selection.

Natural Selection

  • Natural Selection: Organisms become more adapted to their surroundings to survive and reproduce.
  • Survival of the Fittest: Adapted organisms are more likely to survive and reproduce.
    • Example: Deer mice changing color in sand hills for predator protection.

On the Origin of Species

  • Darwin's Book: Describes evolution and how it works.
    • Key principle: All species evolved from simple life forms over billions of years.

Speciation

  • Speciation: Formation of new species when phenotypes become distinctly different.
    • Key determinant: Inability to interbreed and produce fertile offspring.

Speciation Example

  • Geographical isolation leading to reproductive barriers and formation of new species.
    • Example: Monkeys separated on islands evolving into different species.

Selective Breeding

  • Selective Breeding: Breeding plants and animals with desired traits.
    • Aims: Breed for particular genetic characteristics.

Selective Breeding in Plants

  • Selectively bred for:
    • Large fruits
    • Disease resistance
    • Aesthetic beauty.

Selective Breeding in Animals

  • Selectively bred for:
    • Increased meat yield
    • Increased milk yield
    • Large eggs
    • Desirable characteristics (e.g., gentle nature in dogs).

Selective Breeding Step-By-Step

  1. Choose parents with desired characteristics from a mixed population.
  2. Breed selected parents together.
  3. Breed offspring with desired characteristics.
  4. Continue this process over generations.

Selective Breeding Positives

  1. Economic benefit: Increased yields and revenue.
  2. Domesticating animals: Safer and more docile animals.
  3. Prevent disease: Develop disease-resistant.

Selective Breeding Negatives

  1. Selecting for rare diseases: Can accidentally select for undesirable traits.
  2. Reduced genetic variation: Decreases resilience to diseases and pests.