Natural Selection Notes

Charles Darwin- first to propose the theory of evolution (how organisms change over time) after a trip to the Galapogos Islands.

- In 1859, Darwin published his ideas in the book, The Origin of Species

Galapagos Islands- chain of islands off the coast of South America- Each island is very different and isolated from outside predators- There’s competition among the organisms to survive- Even in the most inhabitable parts, there were some organisms able to

survive. Why?

Theory of Natural Selection- The survival rate of offspring- children must survive to pass on traits- The struggle for existence- competition for resources. Limited resources

become limiting factors. Examples: Water, Food, Shelter- Variety within a population- differences between species may make some

better adapted to their environment making them better able to survive making them better able to reproduce giving them a chance to pass those traits onto their offspring.

- Populations change over time- an organisms ability to adapt will help it survive

- Descent with modification- Organisms today have come from and made themselves different from organisms of the past. All organisms have a common ancestor/ descendent.

Staying alive- Mimicry- Copying another organism in order to survive

o Example= the king snake is brightly colored like the coral snake, but only the coral snake is poisonous

- Trickery- Using color tricks to confuse predatorso Example= The butterfly fish has a false eyespot on its fin so predators

can never tell which way the fish is facing- Camouflage- Being able to blend or hide in the surroundings

o Example= snow fox or the peppered moth- Tolerance- Building up resistance to something over time

o Example= Antibiotic resistant bacteria due to over use

Fossil Evidence- Darwin collected fossils to see how organisms changed over time:- Homologous structures- similar physical structure (make-up), but with

different useso Example= Bat wings, whale flippers, human hand, and dog’s paw

- Analogous structures- similar function, but different in physical structure (make-up)

o Example= Butterfly and bat wings- Vestigial organs- organs that remain but no longer have a function (job)

(may be reduced in size)o Example= appendix, eyes of cave dwelling organisms, pelvic bones of

whales and dolphins- Embryology- study of how organisms develop. Focuses on the similarities

during development even though the adults look different