Evolution and Evidence of Change

Evolution

• Cumulative change in heritable characteristics of a population over time
• Species are groups of organisms that can interbreed and produce fertile offspring, sharing common characteristics
• Variation (environmental and genetic) influences chances of survival and reproduction
• Natural Selection is a key driver of evolution: individuals with advantageous traits survive longer, reproduce more, and pass on their traits
• All species have evolved from pre-existing ones

Evidence for Evolution

• Fossil Record: Preserved remains of organisms show changes over millions of years
• Radiometric Dating: Studying the natural radioactivity of fossils to determine their age
• Selective Breeding: Humans intentionally choose desirable traits to breed in plants and animals (artificial selection)
• John Endler's Guppy Experiment: Demonstrated that predator presence influences guppy coloration, with more colorful males found in areas with fewer predators
• DNA Base Sequence Comparison: Highlighting similarities and differences between species
• Mitochondrial DNA (mtDNA): Mutates faster than nuclear DNA and is not mixed with the father's DNA, making it useful for tracking recent evolutionary relationships

Speciation

• Formation of new species from existing populations through isolation and different evolutionary paths
• Population: A group of organisms of the same species living in the same area at the same time
• Barriers to gene flow between populations drive speciation:
  • Geographical Separation: Physical barriers like mountains, rivers, or roads
  • Temporal Differences: Breeding at different times
  • Behavioral Differences: Incompatible mating rituals
• Sympatric Speciation: Occurs within the same geographical area
• Allopatric Speciation: Occurs in different geographical areas
• Example: Bonobos and Chimpanzees are geographically separated
• Infertile Hybrids: Offspring of two different species, often sterile due to chromosome incompatibility (e.g., mules with 63 chromosomes)

Gene Pool and Evolution

• Gene Pool: All the genetic information in a reproducing population
• Allele Frequency: Proportion of a specific gene variant in a population
• Genetic Drift: Random changes in allele frequencies, especially significant in small populations, leading to genetic divergence between isolated groups
• Gradual Evolution: Species evolve slowly and continuously over long periods of time through the accumulation of small, incremental changes.

Explore the fundamental concepts of evolution, including natural selection and species interbreeding. Discover the evidence supporting evolution, such as fossil records and selective breeding. This quiz will test your understanding of how species adapt and evolve over time.