Natural Selection Objective 2-3 Artificial Selection (Selective Breeding) • Nature develops all traits • Humans choose which traits they like and use selective breeding to manipulate the traits • Darwin witnessed this in domestic animals: dogs, cats, cows, etc. • He used this observation to develop the concept of Natural Selection Natural Selection • Darwin defined how nature chooses what lives and what dies as Natural Selection: 1. Struggle for existance • Animals are always competing to survive 2. Survival of the Fittest • Those animals with the best traits to survive in their specific environment are more likely to live and reproduce • Their children would also have the useful traits Natural Selection 3. Descent with Modification • • • Each generation is slightly different from the one before it After 1,000s of generations a species can look very different Common Descent: if you go back in time far enough, every living thing is related Darwin’s Theory of Evolution 1. Individual organisms differ, and some of this variation is heritable. 2. Organisms produce more offspring than can survive. 3. Because more organisms are produced than can survive, they compete for limited resources. Darwin’s Theory of Evolution 4. Individuals best adapted to their environment survive and reproduce most successfully. These organisms pass their heritable traits to their offspring. 5. Species alive today are descended with modification from species that lived in the distant past. If you go back far enough all life on this planet is linked in one great tree of life.