Understanding Evolution in terms of Genetics

DARWIN’S UNDERSTANDING VS. PRESENT DAY How are inheritable traits passed? How do variations appear? Today’s understanding of genes, DNA, variation, and mutations is central to our understanding of how evolution works

Bigger Picture MICROEVOLUTION MACROEVOLUTION Mutations Natural selection + 3.8 billion years = Macroevolution Genetic Drift Gene flow Mutations & Gene shuffling Natural selection of traits Single gene traits Polygenic traits Genetic drift Gene flow Adaptive radiation Convergent & divergent evolution Coevolution Gradualism Punctuated equilibrium Mass extinction Bigger Picture Smaller Picture

POPULATIONS AND GENE POOLS Population: group of the same species that interbreed Gene pool: consists of all genes, including all the different alleles, that are present in a population Large gene pool High genetic diversity Increased chances of biological fitness & survival Small gene pool Low genetic diversity Decreased chances of biological fitness & extinction

Microevolution – Mutations & Gene Shuffling Not all mutations are harmful Some mutations can actually be beneficial & increase organism’s fitness Gene shuffling will produce different phenotypes No change the relative frequency of alleles in the populations

Microevolution – Natural selection of Traits Single Gene Traits Polygenic traits Controlled by a single gene that has two alleles Variation only leads to two possible phenotypes Represented with a bar graph Controlled by two or more genes Polygenic traits have many possible genotypes and phenotypes Represented with a bell shaped or “normal distribution” curve Ear lobe attached Ear lobe detached

Effect of Natural selection on Single Gene traits Changes in allele frequencies Evolution

Effect of Natural selection on polygenic traits

Directional selection A single phenotype is favored Due to environmental changes

Stabilizing selection An intermediate phenotype is favored More homogenous population

Disruptive selection Often extreme phenotypes are favored Main driving force behind speciation

Microevolution – Genetic Drift Genetic drift: Large changes in allele frequencies due to a random event Small gene pool Low genetic diversity Decreased chances of biological fitness & extinction FOUNDER EFFECT BOTTLE NECK EFFECT

FOUNDER EFFECT BOTTLENECK EFFCT

Microevolution – Gene flow

Speciation Behavioral Isolation: Differences in traits or habits

Speciation Geographical Isolation: Land separation of individuals

Speciation Temporal Isolation: Mating season is different

Evolution of Darwin’s Finches 1 2 3 4 5

Macroevolution Patterns Adaptive radiation

Habitat & Niche Habitat: It is the place where an organism lives (Where do you live?) Niche: The niche refers to the role of the organism in the system (What do you do?)

Convergent Evolution Penguin Seal Bird Mammal No common ancestor

Divergent Evolution Polar Bear Brown Bear common ancestor

Macroevolution Patterns Coevolution

Macroevolution Patterns Gradualism Punctuated equilibrium

Macroevolution Patterns

Cretaceous-Tertiary mass extinction (aka- K/T extinction) Wipe out of Dinosaurs Triassic-Jurassic mass extinction Many marine reptile, amphibians were lost Permian mass extinction (aka Great Dying) 96% of species died. All life on Earth today is descended from the 4% of species that survived Late Devonian mass extinction Three quarters of all species on Earth died out Ordovician-Silurian mass extinction Lots of sea creatures were lost

Macroevolution Patterns Convergent Evolution Divergent Evolution