Evolution

History of the theory Jean-Baptiste Lamarck  one of the first to recognize organisms have changed Published ideas in 1809 Proposed that through selective use or disuse of organs, organisms could acquire or lose certain traits during their lifetime He did not understand how traits were inherited, but he realized that organisms adapt

Thomas Malthus  1798 published a book that said the human population was growing faster that the earth could supply He was afraid that the growing population would result in not enough living space or resources

Darwin's observations Darwin sailed around the world on the H.M.S. Beagle in 1831 took 5 years He noticed that the same type of animals had noticeable differences On each island, he would see different traits unique to that particular island Published observations in On the Origin of Species

Natural Selection Darwin’s evolution explanation Struggle for existence – all organisms compete for resources Survival of the fittest – each organism has an environmental fitness This fitness is the result of adaptations Whoever is the most fit for the environment will survive

Certain traits are beneficial and enable the organism to survive These will be passed on to future offspring's He also proposed that “bad” traits will not be passed on

Evidence for evolution Structural Adaptations Mimicry camouflage Physiological adaptations Changes in metabolic activities Fossils Biochemistry Nearly all organisms share DNA, ATP, and enzymes Embryology At one point, all embryos look similar

Mimicry

Camouflage

Bacterial Adaptations

Anatomy Homologous structures Analogous structures Similar in arrangement and function Forelimbs in crocodiles, whales, birds Analogous structures Similar function, different structure wings Vestigial structures No modern-day purpose Ostrich wings, pelvic bones in whales

Vestigial Structures

Homologous structures

Mechanisms of Evolution Populations, not individuals, evolve Gene pool – all of the population’s genes put together into 1 pool Allelic frequency - percentage of a specific allele within the population If alleles stay the same  genetic equilibrium Anything that changes the alleles results in evolution

Natural selection and variation Some variations may increase or decrease chances of survival Stabilizing – favors the average individuals Directional – favors one of the extreme variations of a trait Disruptive – both extremes are favored

Evolution of Species Speciation  process that produces two species from one Reasons: Geographical isolation Reproductive isolation Changes in the gene pool Ecological competition Continued evolution

Patterns of Evolution Adaptive radiation  species evolve to fit habitats Divergent radiation  members of a species become less alike (adapt to environment) Convergent evolution  unrelated species become more alike