Charles Darwin and Evolution

• Charles Darwin developed the Theory of Biological Evolution.
• In 1831, Darwin sailed on the HMS Beagle for a 5-year voyage.

Patterns of Biodiversity

• Species vary globally, locally, and over time.

Scientists Who Influenced Darwin

• Hutton (1785): Connected geological processes with Earth's features.
• Lyell (1830): Past geological processes are still at work today.
• Lamarck (1809): Proposed the concept of use and disuse of organs.
• Malthus (1798): Pointed out that more people are born than die, leading to overcrowding.

Natural Selection

• Artificial Selection: Nature provides variation, and humans select desired traits.
• Struggle for existence: Competition among organisms.
• Variation and Adaptation: An inherited trait that increases an organism's chance of survival.
• Survival of the fittest: The ability to survive and reproduce.
• Natural Selection: The best-adapted individuals survive.
• Biogeography: The study of where organisms live now and how they evolved from their ancestors.
• Close relatives can exhibit differences (Darwin's finches).
• Distant relatives can show similarities (ostriches, emus, rheas).
• Evolution: Change over a very long period.
• The scientific theory of evolution explains how living things descended from earlier organisms.
• Understanding evolution helps us understand the history of life on Earth.
• Evidence supports the theory of evolution from the fossil record, DNA and protein structures, similarities in body structures, and similarities in early development.
• Earth is approximately 4.5 billion years old.

Fossil Record

• The fossil record provides evidence of evolution.
• Fossils show the history of life on Earth and how organisms have changed over time.

Primates

• Characteristics: Forward-facing eyes, opposable thumbs, omnivorous teeth, complex social organization.
• Modern humans, gorillas, and chimpanzees evolved from common ancestors.
• All human ancestors and current humans belong to the biological family Hominidae.

DNA and Protein Structure

• Genes: Segments of DNA that determine an organism's characteristics.
• The more similar the DNA, the more closely related the species.
• The universality of DNA supports the theory of a common ancestor for all species.
• Molecular evidence includes similar genetic code and homologous molecules.
• Cytochrome c, a protein involved in respiration, is an example of a homologous molecule.

Homologous Body Structures

• Homologous structures are similar structures inherited from a common ancestor.

Similarities in Early Development

• Vertebrates (e.g., chickens, turtles, rats) look similar in their early stages of development.

Vestigial Organs

• Vestigial organs are traces of homologous organs that serve no useful function (e.g., the human appendix).

Analogous Structures

• Analogous structures share a common function but not a common structure (e.g., bird wings and bee wings).

Genetic Equilibrium (Hardy-Weinberg Principle)

• Conditions for genetic equilibrium:
  • No mutations
  • No immigration or emigration
  • Random mating
  • Large population size
  • No natural selection

Disruption of Genetic Equilibrium

• Non-random mating (sexual selection)
• Small population size
• Immigration/Emigration
• Mutations
• Natural Selection

Molecular Evolution

• Molecular clock: Uses mutation rates to estimate the time of evolution.

Earth's Early History

• Earth's early atmosphere consisted of CO2, water vapor, nitrogen, CO, HS, and hydrogen cyanide.
• Miller and Urey produced amino acids.
• Free oxygen was initially produced by photosynthetic bacteria.
• Endosymbiotic theory: Ancient prokaryotes entered and remained within eukaryotic cells.
• Mitochondria and chloroplasts resemble ancient prokaryotes.

Formation of Early Cells

• Microspheres: Proteinoid bubbles.
• RNA and DNA: DNA was synthesized from RNA.
• Free Oxygen: Produced by photosynthesis.
• Vestigial Structure: Inherited structure with little or no function (e.g., snake legs).

Galapagos Finches

• Beaks are used for different functions.
• Heritable traits and variations contribute to differences in fitness.
• An organism's genotype is its particular combination of alleles.
• An individual's genotype and environmental conditions produce its phenotype.
• Phenotype: Includes all physical, physiological, and behavioral characteristics of an organism.

Natural Selection and Phenotype

• Natural selection acts directly on phenotype, not genotype.
• Individuals with phenotypes better suited to their environment produce more offspring.
• Gene pool: All genes in a population.
• Allele frequency: How often an allele occurs in a population.

Genetic Variation

• Mutations: Changes in genetics.
• Recombination: Change from sexual reproduction.
• Lateral Gene Transfer: Unicellular organisms exchange genes.

Single-Gene Traits

• Single-gene traits can change phenotypes; the trait is controlled by one gene.

Genetic Drift

• Genetic Bottlenecks: Quick population reduction, leading to a reduction in diversity.
• Founder Effect: A small subgroup migrates and colonizes a new habitat.

Types of Selection

• Directional Selection: One end of the curve survives.
• Stabilizing Selection: The middle of the curve survives.
• Disruptive Selection: Outer ends survive, creating new distinct phenotypes.