Speciation and Extinction February 17, 2016

Evolution – genetically controlled changes in physiology, anatomy, and behavior that occur to a species over time –Microevolution – –Macroevolution – Speciation – development of two or more generically differentiable species from a single common ancestor

Mechanisms of Genetic Differentiation Mutation Genetic Drift Natural Selection Gene Flow Adaptation and Gene Flow

Genotypic Variation

Phenotypic variations – differences in physiology, anatomy, and behavior of different species or individuals of the same species –Spruce tree in forest versus spruce tree at treeline

Allopatric speciation

Sympatric Speciation and Adaptive Radiation

Sympatric Speciation

Extinction Extinction is the loss of all individuals in the population of a given species, genus, family, or order –Local extinctions: American buffalo (Bison bison)

Mass Extinction

Trophic cascades – when the loss of a prey species causes further ecosystem disruptions because of the loss of food for higher predators

Phyletic extinction – pseudoextinction – species evolve into new species with many of its genes persisting in descendant species Example: Hyracotherium to Equus

Dinosaur Extinction KT Boundary – geologic boundary between the Cretaceous and Tertiary 65 mya A large amount of iridium at this boundary indicated large meteor or comet slamming into Earth Large amounts of shock quartz and evidence of large fires found at this boundary The collision of meteor and Earth caused fires, tsunamis, followed by nuclear winter, and then extreme greenhouse effect

Red Queen Hypothesis – If a species cannot evolve fast enough to keep up with competing species, it will become extinct Could lead to an evolutionary trap – overspecializing in an isolated area Or blind alleys – when genetic diversity is lost during evolution, making environmental changes more problematic

Those prone to extinction: –Larger animals –Species with complex behavioral, morphological, or physiological adaptations –Predators at the top of food chain –Specialists species –Species with small population size –Species with low birth rates, or long gestation periods –Species with small geographic ranges –Poor dispersal capabilities