The Theory of Evolution: Natural Selection and Artificial Selection

Charles Darwin English scientist (1809 – 1882) Took the HMS Beagle to South America At the age of 21 took a job on HMS Beagle Five year journey Collected specimens Galapagos Islands As ship’s naturalist, Darwin studied and collected biological specimens (including fossils) at each port

Darwin and Natural Selection For the next 22 years, Darwin developed his theory. Other scientists’ findings influenced Darwin…. Charles Lyell Geologic processes are result of gradual changes that happen over time Malthus Animals produce more offspring that can survive Animals must struggle to survive

Darwin’s Conclusions: Populations possess an enormous reproductive potential Population sizes remain stable (Malthus) Resources are limited Individuals compete for survival There is variation among individuals in a population Only the most fit individuals survive to reproduce Evolution occurs as advantageous traits accumulate over time

Adaptations An adaptation is any variation that aids in an organism’s chance for survival. Types of adaptations: Mimicry – structural adaptation that enables one species to resemble another species Camouflage - blending with surroundings

Which is dangerous? Can you tell? Mimicry Yellow jacket wasp vs. Syrphid fly Which is dangerous? Can you tell?

Mimicry – one of these is poisonous. Coral Snake King Snake

Camouflage Blending in with the environment to hide from predators or prey. This includes seasonal color changes

Camouflage

Camouflage

Artificial Selection Definition: breeding organisms with specific traits for those traits Selective Breeding Most of the time occurs because human preferences or needs. Shows that organisms can change through breeding.

Evolution is… the change in the heritable traits of a population or species from generation to generation.

Natural Selection Definition: mechanism for change in a population Favorable traits are chosen Change in genotype  genetics a force in nature that works like artificial selection Who or what has a better chance of survival long enough to reproduce.