Charles Darwin and Natural Selection Evolution Primer #2 Evolution Primer #2 Who was Charles Darwin? Who was Charles Darwin? Theory of Acquired Characteristics Gain or lose features based on overuse or non-use of them. Would pass this trait onto offspring. Lamarck Example Giraffes have long necks because they stretched them to reach food in high places. Characteristic then passed onto offspring. Other Examples? Theory Discarded Lamarcks theory proved to be illogical Car Accident/Amputation Example Charles Darwin HMS Beagle Galapagos Islands Suspected that small gradual changes might lead to new species over time. Natural Selection Individuals in a population show differences, or variation. Variations can be inherited. Some competition would lead to the death of some individuals while others will survive. Individuals that have advantageous variations will be more likely to survive and reproduce. 1. Individuals in a population show differences, or variation. 2. Variations can be inherited. 3. Some competition would lead to the death of some individuals while others will survive. REVIEW ALERT! What are some factors that organisms compete for? 4. Individuals that have advantageous variations will be more likely to survive and reproduce. Interactive Activities: Natural Selection Visualizing Natural Selection Visualizing Natural Selection Visualizing Natural Selection Basic Principles of Natural Selection Basic Principles of Natural Selection Basic Principles of Natural Selection Virtual Peppered Moth Simulation Virtual Peppered Moth Simulation Virtual Peppered Moth Simulation Natural Selection video clip Natural Selection video clip Natural Selection video clip Darwins Galapagos Island Observations Species on the Galapagos Island closely resembled species found on mainland South America even though the environments were not very similar. Why is this the case? Darwins Finches Observation: Finches of Galapagos Islands looked very similar except for shape of their beak. Darwins observations Organisms were originally from South America Organisms began to change after leaving South America and arriving at the Galapagos. Darwins Finches Conclusion: Finches came from common ancestor. EXPLANATION: Different shape of beak was adaptation for eating a particular food source. Adaptations and Evolutionary Strategies A trait shaped by natural selection that increases an organisms reproductive success. Fitness: measure of the relative contribution an individual trait makes to the next generation. How many viable offspring does an organism provide to the next generation? Types of Adaptation Camouflage Mimicry Compare Mimicry and Camouflage. Antimicrobial Resistance For almost every antibiotic, at least one species of resistant bacteria exists. Cannibalism Feathersall-over-but-crying-and-burial.html Mechanisms of Evolution EVOLUTION OCCURS AT THE POPULATION LEVEL, WITH GENES AS THE RAW MATERIAL. Hardy-Weinberg Principle If allele frequencies do not change, the population will not evolve. In order for this to happen, 5 conditions need to be met. 1. No Genetic Drift! Genetic Drift change in allelic frequencies in a population that is due to chance. Founder Effect Bottleneck 2. No Gene Flow! No new genes can enter the population and no genes can leave the population. Migration increases genetic variation within a population and reduces differences between populations. 3. Mating must be random This rarely ever happens. Why? 4. No mutations Mutation random change in genetic material. Mutations can change the alleles in a population (sometimes even for the better). 5. No natural selection. HW requires that all individuals in population be equally adapted to their environment and thus contribute equally to the next generation. Does this happen!?!? Types of Natural Selection Stabilizing Selection Directional Selection Disruptive Selection Stablilizing Selection Eliminates extreme expressions of a trait when the average expression leads to higher fitness. Example: baby weight Directional Selection An extreme version of a trait makes an organism more fit. Example: Peppered moth Example Disruptive Selection Splits population into two groups: Removes individuals with average traits, but retain individuals expressing extreme traits. Example Speciation A population diverges and then is reproductively isolated. can no longer interbreed or produce fertile offspring with one another Different species result TWO MAIN TYPES Allopatric Speciation Sympatric Speciation Allopatric Speciation A physical barrier divides one population into two or more populations. Examples: mountain ranges, channels, wide rivers, lava flows Grand Canyon Speciation? Kaibab and Albert Squirrels Sympatric Speciation A species evolves into a new species without a physical barrier. They live side by side. Examples: apple maggot flies diverging based on fruit they eat Patterns of Evolution Divergent Evolution Two or more related species become more and more DIFFERENT as a result of new habitat or opportunity. Red Fox Kit Fox Patterns of Evolution Convergent Evolution Unrelated species become more and more alike in appearance as they adapt to the same kind of environment Co-evolution The relationship between two species is so close that the evolution of one species affects the evolution of the other. Ex: Moths foot long tongue Rate of Speciation Traits may change rapidly or slowly. Rates of Speciation: Gradual Equilibrium Punctuated Equilibrium Rates of Speciation Gradual Equilibrium Evolution proceeds in small, gradual steps. Supported by a great deal of evidence. HOWEVER, fossil record contains instances of abrupt transitions. Example: snail shells Punctuated Equilibrium Rapid spurts of genetic change cause species to diverge quickly; these periods punctuate much longer periods when species show little change. Accounts for abrupt changes in fossil record.