Transcript Evolution
Evolution Life Science #3, #4 & #5 Vocabulary • Adaptation • Genealogy • Co-evolution • Homologous Structure • Evolution • Natural Selection • Fossil Record • Paleontologist Evolution • The study of genealogy is limited by human memory and recorded history, but that’s not the case with evolution. • Although no one knows for certain how life on Earth began, scientists have collected evidence explaining how it came to have so much variation. Natural Selection • The changes attributed to evolution take generations of species to appear. • The process of natural selection explains how organisms change over time. • Charles Darwin and Alfred Wallace both contributed to this theory. Natural Selection: Idea #1 • Survival is difficult. • Pressures like drought, flood, disease, and shortages of food or shelter affect all ecosystems. • Organisms compete with other species – and with individuals from their own species – for the food, water and shelter needed for survival. Natural Selection: Idea #2 • Organisms may have adaptations that help them deal with these pressures. • Adaptations can be physical or behavioral. • If an organism possesses a helpful adaptation, it has a greater chance of surviving and reproducing. • The survivor passes on the helpful adaptation to its offspring, multiplying the number of individuals with that adaptation. Natural Selection: Idea #3 • Over long periods of time, this process of natural selection causes new species to arise from old species. • These older species descend from still older species. • The logical conclusion about this process is that all organisms relate to each other by common descent from some original species of life. Evolution: Evidence • Like all other scientific theories, evolution relies on evidence for its support. • Structural similarities between the forelimbs of mammals, called homologous structures, point to a common ancestor that also had this structure. Homologous Structures Evolution: Evidence • The fossil record also provides ample evidence of evolutionary change over time. • All species evolve to meet the demands of specific environments. • If that environment changes quickly, a species that specializes typically cannot adapt quickly enough to survive. Evolution: Evidence • The fossil record also provides evidence of how the environment in a particular place has changed over billions of years. – Example: if sea fossils are found in a place that is now dry land, there used to be sea covering that area. – Example: Remains of animals that lived only in certain temperatures tell about the climate.