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 predators

o  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 uses

o  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