Evolution Chapter 15

Darwin Charles Darwin – father of evolution The Origin of Species – Darwin’s book Darwin's book only uses the word evolution on the last page Evolution - cumulative changes in groups of organisms through time Natural Selection is a means to explain how Evolution works

Darwin’s Theory Survival of the fittest – the species that is best fit to survive will reproduce more, making their genetics more dominant. The weak animals die off and never reproduce, so those genes are not passed down to the next generation

Darwin’s Theory Natural Selection does NOT equal Evolution It is only a means to explain evolution

Darwin’s Theory Artificial Selection - hand selecting certain characteristics for breeding purposes ex. domesticated dogs Variation - individuals in a population differ from one another ex. height of the sunflowers Heritability - Variations are inherited from parents ex. Tall sunflowers produce tall sunflowers, and short produce short

Sunflower expamle Overproduction - Populations produce more offspring than can survive ex. Each sunflower has hundreds of seeds, however only a few will germinate Reproductive Advantage - Some variations allow the organism that possesses them to have more offspring than the organism that does not possess them ex. In this habitat shorter sunflowers reproduce more successfully Overtime - the average height of the sunflower population is short, because the shorter ones reproduce more successfully and the taller ones die off

Sunflowers con’t Overtime - the short sunflowers may become a new species if they are unable to breed with the original sunflowers Natural Selection - through time nature modifies a population to produce new species

Evidence of Evolution Fossil Record - a history of fossils displaying evolutionary changes Derived Traits - newly evolved features that do not appear in the fossils of common ancestors ex. Feathers Ancestral Traits - primitive features that appear in the fossils of common ancestors ex. Teeth, tails Transitional fossils - provide detailed patterns of evolutionary change, display both derived and ancestral traits

Evidence of Evolution Homologous Structures - anatomically similar structures inherited from a common ancestor Predicts that body parts are modifications of ancestors rather than new body parts Vestigial Structures - structures that are the reduced forms of functional structures in other organisms ex. molars, appendix, hairy bodies, etc

Evidence of Evolution Analogous structures - structures used for the same purpose and look similar, however they are not inherited from a common ancestor ex. an eagle wing, and a beetle wing Comparative embryology - comparing vertebrate embryos, they are very similar during different stages of development, they display homologous structures Embryo - early, pre-birth stage of an organism's development

Evidence of Evolution Geographic Distrubution - South America mainland vs. Galapagos Islands Migration patterns explained plant diversity on islands (seeds, wind, bird droppings) Biogeography - study of the distribution of plants and animals around the world

Evolution Adaptation - a trait shaped by natural selection that increases an organism’s reproductive success Fitness - a measure of the relative contribution an individual trait makes to the next generation ex. the number of reproductively viable offspring that an organism produces in the next generation Camouflage - adaptations that allow them to blend in with their environment Mimicry - one species evolves to resemble another species

Evolution terms Hardy-Weinberg Principle - when allelic frequencies remain constant, a population is in genetic equilibrium, so even if populations grow they will grow in the same ratio. Genetic Drift - any change in the allelic frequencies in a population that is due to chance founder effect - when a small sample of a population settles in a location separated from the rest of the population (alleles that were common in one place may now be very uncommon in the new place) Bottleneck - when a population declines to a very low number and then rebounds. The gene pool is greatly reduced and reduces diversity

Darwin’s Finches

Types of Natural Selection Stabilizing selection - eliminates extreme expressions of a trait ex. human babies born with either above or below normal weights have a smaller chance of survival than average weight babies, as a result the average baby weight for humans is a small range Directional selection - when an extreme version of a trait makes an organism more fit ex. peppered moths Disruptive Selection - splits a population into two groups, removes individuals with average traits Sexual Selection - when males and females differ significantly in appearance ex. peacocks

Peppered Moths http://www.techapps.net/interactives/pepper Moths.swf </exchweb/bin/redir.asp?URL=http://www.t echapps.net/interactives/pepperMoths.swf>

Reproductive Isolation Prezygotic isolation - when reproduction is prevented by making fertilization unlikely ex. Eastern and Western Meadowlarks look the exact same, but they have different mating songs Postzygotic isolation - when fertilization has occurred but offspring cannot develop or reproduce ex. Ligers, donkeys

Speciation Allopatric - a physical barrier divides one population into two or more populations ex. mountain ranges, rivers, canyons Sympatric - when a species evolves into a new species without a physical barrier ex. mutations

Patterns of Evolution Adaptive Radiation - divergent evolution, many species evolve from one common ancestor in a short amount of time, happens when there are new niches ex. Cichlids - 300 species evolved from 1 in the past 14,000 years Convergent evolution - when unrelated species evolve similarly even though they live in different parts of the world, happens because of similar ecology and climate Gradualism - evolution proceeds in small, gradual steps Punctuated equilibrium - rapid spurts of genetic change cause species to diverge quickly causing abrupt changes

Chapter 14/15 Test 19 short answer questions Types of fossils Relative and Radiometric Dating Geological time scale Theories of early life (spontaneous generation, biogenesis, etc) Micro vs Macro Evolution Darwin and the Galapagos Islands Artificial and Natural Selection Homologous Structure, Analogous Structures Finches Postzygotic Isolation Peppered moth's Process of Evolution

Chapter 15 Review p 445 - 1-7, 10-13 p 446 - 14-17, 19-20, 23-26