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Chapter 15: Evolution15.1 Darwins Theory of Evolution by Natural Selection ONLY COPY UNDERLINED MATERIALCharles DarwinNaturalist Credited for the concept of EvolutionFather of Evolution

How it all beganDarwin is invited on an epic journey1831: HMS Beagle sets sail from England to survey the coast of South America5 year voyageHis job was to collect biological and geological specimens during the ships travel.He noticed many plants & animals were well suited to their environment.

Galpagos Islands1835: The Beagle stops at the Galpagos Islands, recently formed volcanic islandsLocated 500 miles off the coast of EcuadorEach island has a very unique climateThe animals on the islands lived nowhere else in the world, but, looked like species from South America, but these two places have different environments

Darwins FinchesDarwin found many different birds on the Islands, thinking each one was a different type of birdHe was amazed to learn that all 14 species were finchesTHERE WAS ONLY 1 SPECIES ON THE MAINLAND

DarwinDarwin wondered - If the finches came from the mainland, why were they so different now?He suspected that populations from the mainland changed after reaching the islandsHypothesis: New species could appear through small changes in ancestral species but how does this process work?Turned to pigeon breedersArtificial SelectionPreviously referred to as selective breedingHe learned that breeders could produce certain traits through directed breedingDarwin thought that if humans could change a species through artificial selection, then perhaps the same process could happen in natureNatural SelectionTheory developed by DarwinExplanation of how evolution works, NOT a synonymBased on 4 principles that explain how traits change over time:VariationsInheritanceOverproductionReproductive Advantage1. VariationsIndividuals in a population show differences or variations

2. InheritanceVariations are inherited, meaning they are passed down from parent to offspring

3. OverproductionOrganisms have more offspring than can survive on available resourcesThis creates competition, and a struggle to survive

MMMMMBunny4. Reproductive AdvantageVariations that increase reproductive success will have a greater chance of being passed on than those that do not increase reproductive success SURVIVAL OF THE FITTEST! Faster predator more food, survives longerCamouflaged prey better protection, survives longerAdaptations are central to this principalGiven enough time, natural selection modifies a population enough, and through evolution produces a new species

Natural selection is ALWAYS HAPPENING!Back to our FinchesHe concluded that the different beaks of each finch were inherited variations (changes)These different beaks helped the birds compete for food, survive, and reproduce

Origin of SpeciesDarwin was extremely nervous about publishing his findings, so he continued to collect evidence for his theories for many yearsIn 1859, after 23 years, he published On the Origin of Species by Means of Natural Selection He used the term Evolution on the last page onlyThis term is what biologists use today to define the changes in groups of organisms through timeEvolutionThe changes that occur over time in the hereditary features of a species.

15.2 Evidence of Evolution EvolutionRemember, the theory of evolution states that we all descended from a common ancestorHow do we know evolution has happened on our planet?FossilsAnatomyHomologous, Analogous, VestigialEmbryologyAdaptations

FossilsFossil: remains of once-living things from the pastComparing fossils from older & younger rock layers documents the fact that evolution has occurred; it is a detailed record of evolution.

The Fossil RecordFossils provide a record of species that lived long agoThey show that ancient species share similarities with species that live on Earth now Some show that some species have changed, and that some species have not changed at all

AnatomyHomologous structureAnalogous structureSimilar structure Different forms and functionsInherited from a common ancestor

Different in structure and formSimilar in functionNOT inherited from a common ancestor

Vestigial StructuresType of homologous structureShared structure that has reduced function or no function in some organismsEvolution suggests that over time these structures will be lost

Vestigial StructuresHuman appendix Wisdom teethTailbone (coccyx)

EmbryologyIf you look at different animals during stages of embryonic development you can see common traits. This shows a common ancestry

AdaptationsAdaptation: a trait shaped by natural selection, increases an organisms reproductive success

Fitness: how much a trait contributes to the next generationHow necessary a trait is to survival will determine if it is passed onAdaptationsThere are many kinds of adaptations, they can be physical or behavioralSome adaptations are the consequences of other evolved characteristics, however, these adaptations will not increase reproductive success

AdaptationsThe better adapted an organism is, the higher its chances of survival areAdaptations are at the heart of Darwins theory!

CamouflageAdaptations that allow organisms to blend in with their surroundingsCamouflage varies by species, but their environment is often the most important factor in how they appearBecome almost invisible to predators and prey

MimicryOne species evolving to resemble another species

White-tailed Deer Fake DeathWhen a predator approaches, their heart rate is programmed to drop so low that they enter a state of tonic immobility. The result is that the look dead, which, coupled with its involuntary peeing and pooping that accompanies the heart rate drop, will look pretty unappealing, even to a hungry animal.

Bloody Hippo SweatIt contains zero blood and zero sweat and yet, hippopotamuses secrete what we know as "blood sweat." This keeps their skin moist and protects it from sunburns, as well as many infections.

Exploding Malaysian Ant This adaptation is perhaps the most intense defense mechanism: suicide. When the ant senses its life is at risk, it will often click its own self-destruct button and explode

Northern Fulmar Projectile Vomit All it takes is a tiny confrontation for a fulmar chick to literally throw up chunks of orange puke that is so nasty and sticky, it becomes the foulest prey of all timeGreat Transformations15.3 Shaping Evolutionary TheoryMechanisms of EvolutionNatural selection is not the only way to explain how evolution worksLICEPopulation GeneticsEvery population of a species has a variety of genes, and each gene can have multiple alleles. Gene Pool: All the available genetic information within a population When life is thriving in a population and there is genetic equilibrium, then these alleles are not changing in frequency. There is no selection. There is no evolution. Everything is calm. Like a poolbefore the cannon ball.Population GeneticsHardy-Weinberg Principle: when allele frequencies remain constant, a population is in genetic equilibrium. In other words - when the dominant genes and recessive genes are constant, the POPULATION is in equilibrium

Population GeneticsEvolution cannot occur if alleles in the population are not acted on by forces that cause change! Consider these forces the CANNON BALL!Genetic driftGene flowMutationRandom matingNatural selectionWhen these things are happening, evolution is happening, and Hardy-Weinberg is null and void

Genetic DriftChange in the allele frequency due to chanceFounder effect, Bottleneck effectAn ant gets stepped on, a rabbit gets swept up by a tornado, an elephant drinks up a protozoa living in a puddle, a plane crashes killing a Nobel Laureate.The above events have nothing to do with genotype or phenotype--they occurred purely by chance.

Genetic DriftFounder Effect: Occurs when a small sample of a population settles in a location separated from the rest of the populationAlleles that were uncommon in the original population might be common in the new population. (so the recessives might start showing up, this happens in populations like the Amish)

Genetic DriftBottleneck Effect: Occurs when a population declines to a very low number and then rebounds

Gene FlowNew genes entering the population, and genes leaving the populationThe movement of individuals in and out of populations increases variation within a population, and decreases differences between populations

MutationA change in the original DNA sequence of an organismSome have no effect, however others can lead to the creation of a different protein, which will change the phenotypeNatural SelectionVariation of traitsInheritanceOverproductionSurvival of fittest

SpeciationSpeciationThe formation of two species from a common ancestorA species is a group of living things that can breed with others of the same species and form FERTILE offspring.Allopatric, sympatric

Allopatric SpeciationA physical barrier divides one population into two or more populations.Ocean, river, mountain, glacier, lava, etc.

Abert squirrelKaibab squirrelSpecies FormationDuring the time of their separation, evolution continues to take place in each group.

However, the changes that occur in one group are not the same as the changes that occur in the other they both evolve, but evolve differently

Species FormationThe two groups gradually become different because their environments are different.

In time each group may become a different species.

As a result they would not be able to produce fertile offspring if brought back together

Sympatric SpeciationA species evolves into a new species without a physical barrier.The ancestor species and the new species live side by side during the speciation process.

Patterns of EvolutionPatterns of EvolutionSpeciation is a long, gradual processScientists know it happens because of patterns in evolutionCoevolutionConvergent evolution

CoevolutionSometimes species evolve together!Coevolution: The relationship between two species might be so close that the evolution of one species affects the evolution of the other speciesCoevolutionary arms race antibiotic resistant bacteriaAdaptations and counter-adaptations

Convergent EvolutionUnrelated species evolve similar traits because they live in similar climates, even though they live in different parts of the world.

The Evolutionary Arms RaceThe Minds Big Bang