Evolution Life Science #3, #4 & #5

Vocabulary Adaptation Co-evolution Evolution Fossil Record Genealogy Homologous Structure Natural Selection 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.