Biology: Evolution and Mutations

Mutations

• A mutation is a change in the DNA sequence of an organism, which can affect the structure and function of proteins
• Types of mutations:
  • Point mutations: a change in a single nucleotide
  • Frameshift mutations: an insertion or deletion of nucleotides that alters the reading frame of the genetic code
  • Chromosomal mutations: changes in the number or structure of chromosomes
• Causes of mutations:
  • Errors during DNA replication
  • Exposure to mutagenic agents such as radiation and chemicals
  • Viral infections
• Consequences of mutations:
  • Can be beneficial, neutral, or harmful
  • Can lead to genetic disorders and diseases

Example of a Mutation Leading to a Disease: Sickle Cell Anemia

• A point mutation in the HBB gene leads to the production of abnormal hemoglobin, causing sickle-shaped red blood cells
• This mutation leads to the development of sickle cell anemia, a genetic disorder characterized by anemia, pain, and increased risk of infections

Evolution

• Evolution: the process of change in the inherited characteristics of a population over time
• Evidence for Evolution:
  • Fossils: the fossil record shows a pattern of gradual changes in life forms over time
  • Embryological structures: similarities in embryonic development across different species
  • Vestigial structures: presence of structures that have lost their original function

Natural Selection

• Process by which individuals with favorable traits are more likely to survive and reproduce, passing those traits to their offspring
• Leads to the adaptation of populations to their environment
• Example: Peppered Moths
  • Prior to the Industrial Revolution, moths had a light-colored, speckled appearance, allowing them to blend in with lichen-covered trees
  • With the increase in air pollution, trees became darker, and a genetic variation in the moth population resulted in dark-colored individuals
  • These dark-colored moths had a selective advantage, as they were better camouflaged on the dark trees, and thus were more likely to survive and reproduce

Types of Evolution

• Convergent evolution: similarities in structure and function between different species that are not closely related
• Divergent evolution: divergence of a single species into two or more distinct species
• Homologous structures: similar structures in different species that share a common ancestor
• Analogous structures: similar structures in different species that have evolved independently

Types of Selection

• Stabilizing selection: selects for intermediate traits, reducing variation in the population
• Directional selection: selects for extreme traits, increasing variation in the population
• Disruptive selection: selects for extreme traits in different directions, increasing variation in the population

Mutations

• A mutation is a change in the DNA sequence of an organism
• Types of mutations:
  • Gene mutation: a change in one gene
  • Chromosomal mutation: a change in the number or structure of chromosomes
• Causes of mutations:
  • Errors during DNA replication
  • Exposure to mutagenic agents such as radiation and chemicals
• Consequences of mutations:
  • Can result in genetic disorders or diseases
  • Can lead to evolution of new species

Example of Sickle Cell Anemia

• A mutation in the HBB gene causes sickle cell anemia
• The mutation leads to the production of abnormal hemoglobin, which causes red blood cells to become sickle-shaped
• This can lead to anemia, infections, and other complications

Evolution

• Evolution is the change in the characteristics of a species over time
• Evidence for evolution:
  • Fossils: provide a record of the history of life on Earth
  • Embryological structures: similarities in embryonic development across different species
  • Vestigial structures: structures that have lost their original function but are still present

Process of Natural Selection

• Natural selection is the process by which individuals with favorable traits are more likely to survive and reproduce
• The process of natural selection leads to evolution and speciation
• Example: peppered moths
  • Prior to the industrial revolution, moths were light-colored with dark spots
  • With the increase in air pollution, trees became darker, and a mutation occurred in the moth population, leading to dark-colored moths
  • The dark-colored moths were better camouflaged and more likely to survive, leading to an increase in their population

Convergent and Divergent Evolution

• Convergent evolution: similar environmental pressures lead to similar adaptations in different species
• Divergent evolution: a single species splits into two or more distinct species over time

Homologous and Analogous Structures

• Homologous structures: structures that are similar in different species due to a common ancestor
• Analogous structures: structures that are similar in different species but do not share a common ancestor

Types of Selection

• Stabilizing selection: selective pressure that favors the average phenotype
• Directional selection: selective pressure that favors one extreme phenotype over the other
• Disruptive selection: selective pressure that favors both extreme phenotypes over the average phenotype