EVOLUTION The process of cumulative change in the heritable characteristics of a population One change is not enough to have major impact on species Changes must be passed on genetically from one generation to the next Changes do not effect on individual Evolution takes time Change + Change + Change . . . . . . . . . New species = speciation

The Fossil Record Life that existed more than 500 million years ago was vastly different in appearance Top predators today (mammals) – none existed before the dinosaurs Apart from select species, majority of living organisms today have no similar fossil form Though oceans have existed for majority of earth’s life, fish fossils only date back 500 mya

Aging Fossils After 5730 years, 50% 14C remains, 50% 14N has been created Radioactive Carbon Dating – 14C High 14C – younger bone/shell Low 14C – older bone/shell Decay: radioactive parent isotope (14C) changes into stable daughter isotope (14N) Rate of occurrence = half-life Insufficient 14C, use 40K

Artificial selection Provides a good record of recent changes in heritable characteristics Breeders learned to choose the males and females with the most desirable genetic characteristics and breed them together Certain varieties of animals had unique combinations of characteristics which did not exist before Is evidence that evolution is happening due to an accumulation of small changes over time, however it is certainly not the driving force of evolution in natural ecosystems

Homologous Structures Structures that are similar in form and function but found in seemingly dissimilar species Pentadactyl limbs Shapes and number of bones vary, the general format is the same All species have different mode of locomotion Evidence that the organisms in question have a common ancestor Bones different size, varied morphology – but position is the same Whales could swim with different number of fingers – but have 5

Homologous Structures Shows species divergence Two species can no longer interbreed

Homologous Structures Adaptive Radiation Similar by distinct species evolve relatively rapidly from a single species or small number of species Natural selection or presence of a barrier  causes change position/role within community Exploit slightly different niche more successfully

Lemurs live on Madagascar and Comoro Islands No monkeys or apes present Large variety  adaptive radiation Fossils found on other continents – but none living Some: Live on ground In trees In rainforest In desert Could not compete with monkey/apes

Representation of species with their common ancestor Continuous variation across geographical range Selective pressure Measurable differences in DNA (due to environmental stimuli) Some genes selected for others selected against Overtime - speciation

Transient polymorphism Different versions of a species – caused by mutations Moth: peppered (grey) or melanic (black) Common Mutation in 1% of population During industrial revolution: melanic form increased in numbers (95-100%) reversed cameoflage Blend into their natural habitat – white bark of trees Current day: percentage of type of peppered moth found depends on locale and pollution levels Melanic – 0-30% due to clean air acts