Natural Selection in Action

Ernst Mayr Without speciation, there would be no diversification of the organic world, no adaptive radiation, and very little evolutionary progress. Proposed that Darwin's theory of natural selection could explain all of evolution, including why genes evolve at the molecular level Mayr proposed that when a population of organisms becomes separated from the main group by time or geography, they eventually evolve different traits and can no longer interbreed. 

Mayr’s Observations If all individuals reproduce successfully, a population would grow exponentially! Even so, populations remain stable in size… * except the human population (are we immune to selective pressures??) Resources are limited Individuals in a population are varied Much variation is heritable (can be passed on to offspring)

Variation in populations Genetics is the basis for all variation in populations! DNA contains genes, important chunks of genetic info that code for specific proteins in your body… this defines how you look (your phenotype)!

Mayr’s Inferences There is competition among individuals in a population to survive & reproduce Survival depends on inheritable traits = increased fitness (ability to survive & reproduce) Inequality in fitness of individuals leads to changes in populations over time

Artificial Selection Human modifications of traits by selectively breeding individuals in a population

Adaptations & Heritable Traits Process where population becomes better suited to environment Feature (physical or behavioural) that allows for increased fitness of an individual Product of natural selection * Can’t always be passed on to offspring!! Heritable Traits Traits are specifically linked to genetics of populations Alterations to traits happens at the DNA/gene level * Can always be passed on to offspring!!

Adaptation Examples… * Think about how each of these birds is adapted to its environment & available food.