Evolution Notes Part 2

Evolution Is change in a species over time. Doesn’t happen within one lifetime. Happens as different genes are naturally selected and passed on from generation to generation. Remember that Natural Selection is the survival of the fittest.

Natural Selection in Action Antibiotics: You should always take the entire dose (~10 days) to ensure that you have killed off all the bacteria. Otherwise, those strong ones that survived (were most fit) will go on to reproduce, passing on their antibiotic resistant genes. Before selection Before antibiotic After selection After antibiotic Final population Final population Resistance Level _______________________________________________________ Key: Resistance level

More Natural Selection… The Flu changes & mutates a little each year, and so new vaccines are always needed. Herbicides: Weeds that survive weedkillers pass on those resistant genes to offspring. Pesticides: Mosquito populations change as only some of the mosquitoes are killed by insecticides and the resistant individuals survive to breed. New repellents are needed, often with stronger doses of DEET.

Speciation Is the process of of one species splitting into different species. As groups begin to adapt to different conditions, and eventually become so genetically different that they can no longer interbreed [=different species]. Example: lizards

Reproductive Isolation One way speciation can occur is by reproductive isolation. This is when members of a species are separated (isolated) by distance, mountains, water, etc. and are not accessible to each other for breeding. Over generations, their genes may become incompatible. Example: Northern & Southern Leopard frogs.

Reproductive Isolation: Leopard frogs Northern Southern Missouri

Vestigial Structures Body parts that seem useless now, but may have once been important to an ancestor. Examples: whale hind leg bones, flightless bird wings, goosebumps, human wisdom teeth, (appendix), cave fish eyes…

Homologous Structures Body parts that have the same basic structure and genes across species. Remember “homo” means “same”. A clue that they may share a common ancestor long ago. Examples: forelimbs and embryoes.

Homologous structures: forelimbs Forelimbs of many species have the same basic layout, modified for their needs by evolution. Some fish have the same layout and may have been the first land vertebrates.

Homologous structures: embryonic development

Convergent Evolution To “converge” means come together… Different species in the same environment often have similar adaptations, even though they are not closely related. This is because the same strategies that help one species survive in that environment also work for other species.

Convergent Evolution Example Example: white Arctic animals (foxes, rabbits, owls, geese, polar bears…). White camouflage helps to survive in snow.

Convergent or Homologous? Flight is a good adaptation to have, but not all flyers are related. Bats & Birds seem to have recent common ancestry (homologous), but insects developed flight separately (=convergent).

Evolution Unit Test = May 6th Know terms & examples on Study Guide (You’ll get it Thursday, due next Wed.) Look over other notes and quiz. Flashcards may be helpful. This is your last big unit test before finals. (You’ll still have weekly quizzes on taxonomy & ecology).