Chapter 15

Chapter 15Darwins Theory of Evolutionthe single most important scientific idea that anyone has ever had

15-1 The Puzzle of Lifes DiversityEvolution: change over timeprocess by which modern organisms descended from ancient organisms

Do you remember what a theory is?

Voyage of the Beagle1831- EnglandCharles DarwinRecorded observationsCollected data/specimensProposed evolutionary theory about how life changes over time

Darwins DataDiversityGalapagos Islands- different plants/animals on each islandPatternsReproductive, habitats, etc.Fossils: preserved remains/evidence of ancient organismsConnected old and new

15-2 Ideas that shaped Darwins thinkingOld belief: Earth was young and hadnt changed since life beganDiscoveries in geology:James HuttonGeological changeEffects of natural forces (rain, wind)Happens slowly/constantly

Charles LyellWrote Principles of GeologyEarth has changed over timecould life?

Jean-Baptiste LamarckOrganisms adaptIf you use it, it will stay (get passed on)If you dont, it will go awayTendency toward perfectionInheritance of acquired traits*

Population GrowthThomas Malthus- economistMore people are born than are dyingUncontrolled population growth = high competition for resourcesWhat makes some survive and others die?

15-3 Darwin Presents his case1859- publishes On the Origin of Species:

Evolution has been happening for millions of years and is still happening todayMechanism of evolution = natural selection

Variation and Artificial SelectionGenetic variation found everywhereBreeders use it to make the best:Fastest horsesPlants with biggest fruit

Artificial selection: selection by humans for breeding of desired traits from the natural genetic variation of organisms

Evolution by Natural SelectionDarwin questioned: How does selection happen in nature?

Struggle for existence: competition among members of a species for food, living space, reproduction, etc.

Survival of the FittestProcess by which individuals better suited to their environment survive and reproduce most successfully

Fitness: ability of an organism to survive and reproduceAdaptation: inherited characteristic that increases an organisms chance of survival (structural, physiological, behavioral, etc.)

Survival of the Fittest = Natural SelectionSuccessful adaptations will increase fitnessIf you survive/reproduce, you pass on genes = more of those genes in nature

Descent with ModificationEach living species has descended- with changes- from other species over time

Common descent: all living things come from a common ancestor

Darwins Evidence #1fossil record- organisms have come and gone but can be related/connected to current organisms

Darwins Evidence #2geographical distribution of living species- descent with modificationAs organisms changed, they adapted to different habitats and spread out

Darwins Evidence #3homologous body structures: structures that have different mature forms in different organisms but developed from the same embryonic tissueEx: limbs (arms, wings, flippers)Increased similarities = more closely relatedEx: bats and humans, birds and reptiles

Vestigal StructuresStructures that serve no useful functionHomologous structures that the organisms no longer needsEx: whale legs

Darwins Evidence #4similarities in embryology- many embryos look the samecommon cells growing in similar ways