Warm Up: What does theory mean to you? What does theory mean to you? A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world. A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world.theory

EVOLUTION Chapter 15

Evolution… Charles Darwin: Charles Darwin:  Proposed the idea of Natural Selection  HMS Beagle: 1831  Studied organisms around the world  1859: Published the book Origin of Species

The Galapagos Island: Living Creatures Darwin observed many living creatures: Darwin observed many living creatures:  Land Tortoises-differing shells  Galapagos Tree Cactus  Marine iguanas-swam in the ocean  Finches-differing beak types  Collected 13 different kinds  All differing beaks

Animals

Artificial Selection Breeding traits Breeding traits  Pigeon tails  Dog breeds Selects “best” traits Selects “best” traits Creates change and variety Creates change and variety

Ideas that Shaped Darwin’s Thinking Charles Lyell Charles Lyell  geologist  Earth really old Thomas Malthus Thomas Malthus  Essay that stated humans would compete for space  Darwin applied to natural world

Darwin’s Theory Individuals pass their traits on to massive numbers of offspring Individuals pass their traits on to massive numbers of offspring  Not all can survive

Darwin’s Theory Individuals all have slight variations Individuals all have slight variations  Some variations help them survive better

Darwin’s Theory Animals that survive will have more offspring Animals that survive will have more offspring  Certain variations get passed to more individuals

Natural Selection Individuals with traits favorable for survival will survive, reproduce, and pass these traits on, changing the makeup of the next generation Individuals with traits favorable for survival will survive, reproduce, and pass these traits on, changing the makeup of the next generation “Survival of the Fittest” “Survival of the Fittest”

Natural Selection continued… Animals acquire traits that help increase their fitness (Survival of the fittest) Animals acquire traits that help increase their fitness (Survival of the fittest) Animals do not acquire traits on purpose Animals do not acquire traits on purpose May happen rapidly (humans) or very slowly (sharks, crocodiles) May happen rapidly (humans) or very slowly (sharks, crocodiles)

15-2: Evidence of Evolution Fossils Fossils Biochemistry of life Biochemistry of life Geographic Distribution of Living Things Geographic Distribution of Living Things Similar Body Structures Similar Body Structures Embryological Evidence Embryological Evidence

Evidence for Evolution 1.) The Fossil Record-  Layers show change in animals  Shows transitional species

Evidence of Evolution 2.) Biochemistry  Similar amino acids & proteins  Similar DNA and RNA

Evidence of Evolution 3.) Biogeography Convergent evolution creates similar (but unrelated) organisms in distant lands

Evidence of Evolution 4.) Homologous Structures 4.) Homologous Structures  Similar structures  Divergent evolution of similar trait  NOT convergent evolution (analogous) Similar function due to similar environmentSimilar function due to similar environment

Evidence for Evolution 4.) Homologous Structures 4.) Homologous Structures Vestigial organs-organs that serve no useful function in an organism Vestigial organs-organs that serve no useful function in an organism i.e.) appendix, miniature legs, arms i.e.) appendix, miniature legs, arms

Evidence for Evolution 5.) Embryological Evidence: Embryos look similar in development

Disruption of Genetic Equilibrium: Causes of evolution Mutation: occur naturally, can create totally new alleles change genes Mutation: occur naturally, can create totally new alleles change genes  This can change pop. genes Gene Flow: migration allows (genes  ) Gene Flow: migration allows (genes  ) Genetic Drift: allele frequency changes by random chance (small is affected more) Genetic Drift: allele frequency changes by random chance (small is affected more) Sexual Selection: choosing mates based on certain characteristics Sexual Selection: choosing mates based on certain characteristics

Continued… Natural Selection Natural Selection  1.) Stabilizing selection: individuals w/ an average trait are most likely to survive  2.) Directional selection: more extreme adaptation is likely to survive  3.) Disruptive Selection: either extreme of an adaptation is likely to survive

Wrap-up: Which piece of evolutionary evidence is the most convincing in helping prove evolution? Which piece of evolutionary evidence is the most convincing in helping prove evolution? Why? Why?