Evolution IB Biology 5.4

Definition  “Evolution is the cumulative change in the heritable characteristics of a population.”  Not only is it something that can be observed, but it is a change in the genetic code of the species  For humans, it is not a change we will observe in our lifetime but studies are done on organisms with a short life span and done by farmers in something called selective breeding  The mechanism of evolution is called NATURAL SELECTION – Charles Darwin and the Galapagos Islands  In nature plants and many animals produce large amounts of seeds and eggs to assure the continuation of their species 

Fossil Record  Fossils provide evidence for evolution as all the ones found and studied were SIMILAR to existing organisms  These similarities suggested that the organisms changed over time as the environments they lived in changed and they became adapted to the surroundings  Fossil sequencing matches the expected evolutionary pattern and plant fossils are older than animal in aquatic and land fossils  Algae  fungi  Worms  Fish Amphibians  Reptiles  Birds  Land Vertebrates

Selective Breeding  Domestication of animals  Breeding of required livestock  Egg laying hens vs jungle fowl  The process is called artificial selection – choosing desired traits and mating to acquire more individuals with these traits  The breeding time is much shorter than geologic time so domestication shows evolution

Homologous Structures  Some similarities between structures are superficial – the bird wing and the insect wing – having the same function but different structures  Structures that superficially look different but are structurally the same are homologous – the bat wing and the bird wing have the same bone structure  These do not prove ancestry or evolution but the similarities explain evolution

Speciation and Variation  When some members of the same species become geographically separated, (islands) the characteristics of these divided populations may undergo changes such that they are recognized differently and thus a new species  Variation within a species can develop as well if certain traits allow camouflage of the organism so they do not become prey, these traits will pass to the next generation.

Causes  Mutations – good and bad  Sexual Reproduction and the combination of the gametes (fertilization)  Meiosis ; 2n  n

Natural Selection  Occurs When: * Variation is present * Variation is present * Mutations and sexual reproduction occur * Mutations and sexual reproduction occur * Adaptations are made to the environment * Adaptations are made to the environment * Many offspring are produced * Many offspring are produced  Due to these situations, differential survival and reproduction occur, these inheritances get passed on to future generations and there is a progressive change within the species.

Examples  Using your textbook, Thoroughly explain the two examples of natural selection – steps, methods and results!!!  Peppered moths is another one you can use!