DARWINS THEORY OF EVOLUTION BY NATURAL SELECTION Evolution

DARWIN’S THEORY OF EVOLUTION BY NATURAL SELECTION

Evolution � � � Evolution is change in the heritable traits of biological populations over successive generations Evolutionary processes give rise to diversity at every level of biological organization, including the levels of species, individual organisms, and molecules Evolution acts on existing genetic mutations

Artificial Selection � � Mechanism by which evolution can occur It is most commonly seen with the careful breeding of plants or animals in order to promote traits that suit human preferences

Natural Selection � � Mechanism by which, if given enough time a population could be modified to produce a new species Some competitors in the struggle for existence would be better equipped for survival than others Those less equipped would die or produce fewer offspring Four basic principles � Variation � Heritability � Overproduction � Reproductive Advantage

Variation � Individuals in a population show variations among others of the same species

Heritability � Variations are inherited from parents

Overproduciton � � Populations produce more offspring than can survive Those that are fittest for the environment survive

Reproductive Advantage � Variations that increase reproductive success will be more common in the next generation

Intermediate Forms in the Fossil Record � Fossils provide a record of species that lived long ago and thus supply evidence for evolutionary change

Archaeopteryx � � Archaeopteryx is an intermediate between dinosaurs and birds It had teeth and a tail like dinosaurs It had feathers and a “wishbone” like a bird Most feathers were not flight feathers but downy feathers for communication and insulation