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