Evolution: Natural Selection

Evolution

Natural Selection

• Definition: The process by which organisms that are better adapted to their environment are more likely to survive and reproduce, passing on their advantageous traits to their offspring.
• Key components:
  • Variation in population: Existing differences in traits among individuals.
  • Heritability: Traits are passed down from parents to offspring.
  • Differential reproduction: Individuals with advantageous traits are more likely to reproduce.
  • Adaptation: Traits that increase fitness and survival.

Speciation

• Definition: The process by which a new species emerges from an existing one.
• Mechanisms:
  • Allopatric speciation: Geographical isolation leads to reproductive isolation.
  • Sympatric speciation: Reproductive isolation occurs within a single population.
  • Hybrid speciation: New species emerge from hybridization between two different species.

Fossil Record

• Definition: The chronological record of fossils found in rock layers, providing evidence of evolutionary history.
• Key features:
  • Fossil succession: Fossils found in rock layers, with older fossils found in deeper layers.
  • Transitional fossils: Fossils exhibiting characteristics of both ancestral and descendant species.
  • Biogeography: Fossil distribution patterns provide evidence of evolutionary relationships.

Genetic Drift

• Definition: The random change in allele frequency over time, resulting in genetic variation.
• Mechanisms:
  • Bottleneck effect: Reduction in population size leads to loss of genetic variation.
  • Founder effect: New populations established by a small group of individuals, leading to reduced genetic variation.
  • Genetic hitchhiking: Neutral alleles become fixed in a population due to linkage with advantageous alleles.

Adaptation

• Definition: The process by which an organism becomes better suited to its environment.
• Types:
  • Structural adaptation: Physical changes to the body, such as shape, size, or color.
  • Physiological adaptation: Changes in bodily functions, such as metabolism or temperature regulation.
  • Behavioral adaptation: Changes in behavior, such as migration or hibernation.

Note: These notes provide a concise overview of the key concepts and mechanisms related to evolution, focusing on the subtopics of Natural Selection, Speciation, Fossil Record, Genetic Drift, and Adaptation.

Evolution

Natural Selection

• Better adapted organisms survive, reproduce, and pass advantageous traits to offspring
• Requires variation in population, heritability, differential reproduction, and adaptation

Speciation

• Process of a new species emerging from an existing one
• Mechanisms:
  • Allopatric speciation: geographical isolation leading to reproductive isolation
  • Sympatric speciation: reproductive isolation within a single population
  • Hybrid speciation: new species emerging from hybridization between two species

Fossil Record

• Chronological record of fossils in rock layers, providing evidence of evolutionary history
• Key features:
  • Fossil succession: fossils found in rock layers, with older fossils in deeper layers
  • Transitional fossils: exhibiting characteristics of both ancestral and descendant species
  • Biogeography: fossil distribution patterns provide evidence of evolutionary relationships

Genetic Drift

• Random change in allele frequency over time, resulting in genetic variation
• Mechanisms:
  • Bottleneck effect: reduction in population size leading to loss of genetic variation
  • Founder effect: new populations established by a small group, leading to reduced genetic variation
  • Genetic hitchhiking: neutral alleles become fixed in a population due to linkage with advantageous alleles

Adaptation

• Process of an organism becoming better suited to its environment
• Types:
  • Structural adaptation: physical changes, such as shape, size, or color
  • Physiological adaptation: changes in bodily functions, such as metabolism or temperature regulation
  • Behavioral adaptation: changes in behavior, such as migration or hibernation