Factors in Natural Selection 1. All populations have genetic variation. • All individuals have a slightly different genetic makeup . 2. The environment presents challenges to successful reproduction. • Unsuccessful individuals do not pass on genes.
Factors in Natural Selection 3. Individuals usually produce more offspring than the environment can support. • Creates competition. 4. Better suited individuals produce more successful offspring. • Successful genes take over population.
Evolution in Action: Anole Lizards • Scientists studied Anole lizards of the Caribbean islands: • Cuba, Hispaniola, Jamaica and Puerto Rico. • Each species’ body type correlates to its specific habitat needs: • Trunk/ground dwellers= Stalky bodies; longer legs. • Twig dwellers= Slender bodies; short legs and tails. • Grass dwellers= Slender bodies; long tails.
Evolution in Action: Anole Lizards • Scientists found: • Distinct species with the same body type on different islands. • Hypothesized that each twig-dwelling anole evolved independently on each island from one distant ancestor. • CONVERGENT EVOLUTION: When unrelated species become more similar as they adapt to the same kind of environment.
Evolution in Action: Darwin’s Finches • Darwin collected 16 species of finches • All had different beaks. • All of them evolved from a single ancestor. • Adapted to different food sources. • DIGERGENT EVOLUTION/ADAPTIVE RADIATION: Two or more related but distinct populations become more and more dissimilar as they fit different parts of the environment.
Evolution in Action: Dogs • Today’s domesticated dogs are all descendants of the wolf. • 10,000 years • Originated when relatively tame wolves coexisting with humans were bred, producing increasingly tame wolf ancestors. • Some natural traits are lost in the process.
Evolution in Action: Dogs • Today’s breeds were selected for distinct traits. • Herding Dogs: Eye and Stalk, don’t kill. • Hounds: Chase. • Retrievers: Grab prey, don’t eat. Etc…. • Artificial Selection: The selective breeding of organisms by humans for specific desirable traits.
Evolution in Action: Flowers and their Pollinators • Coevolution: The evolution of two or more species that is due to mutual influence, often in a way that is beneficial. • Shape of plants and flowers fit the specific characteristics of their pollinators.