If evolution is the answer to a scientific question then what is the question Exam 3 What is Evolution Biodiversity Biodiversity Degree of variation of life in a given area Excluding bacteria estimated 9 million species of life on Earth 10 of these are known 900 000 Biodiversity Many more in fossil records 350 000 known species of beetles 250 000 described species of plants Why are there so many different kinds of life Why are some kinds of life more common or more rare than others Why do some species share many characteristics while some share very few How do existing organisms adapt to a changing environment The answer to all of these questions is this Populations of organisms are not fixed that is populations change over time How those populations change is determined by the environment in which they live This is evolution Evolution is Change of heritable characteristics in biological populations across generations What is a characteristic What does it mean for a characteristic to be heritable Why does evolution of organisms depend on characteristics being heritable A change that cannot be passed on to the next generation will die with the current generation http www youtube com watch v GhHOjC4oxh8 Selective Breeding Selective Breeding traits are inherited plant Evolution Charles Darwin Directed evolution of populations of organisms by choosing which Cabbage Brussels sprouts etc all descended from the same mustard All breeds of dogs descended from the gray wolf Name most associated with the scientific idea of evolution The idea that organisms change over time that is evolved pre dates Darwin Darwin s Innovation Recognized that the environment could be the breeder Natural selection Process by which biological traits become more common or less common based on the organism s ability to reproduce within their environment http www youtube com watch v 0SCjhI86grU Natural Selection http www theguardian com science video 2013 jan 25 evolution masterclass darwin video Natural selection Recap Evolution Any change in heritable characteristics in biological populations over Natural Selection Force that causes evolution to occur environment as breeder of Process by which traits become more or less common due to their effect on an organism s ability to reproduce generations organisms The process In biological populations there is a diversity of traits due to genetic diversity Genes are the most important factor in determining traits so diversity of genes necessary for diversity of traits Two sources of diversity New traits are generated by random mutation New combinations of existing traits are generated by random breeding Traits that increase survival reproduction become more common due to greater rate of reproduction and more offspring traits that decrease survival become less common Sometimes this is a balancing act see the example of sickle cell disease In natural selection the environment acts as a breeder choosing which traits flourish and which traits die off How is this possible Darwin and Malthus Thomas Malthus Darwin and Malthus Malthusian trap Controversial and influential economist Studied population growth and effects on economy In all populations of organisms growth of the population is greater than its supply of available resources The point at which the needs of the population exceeds the available supply Darwin Above the Malthusian trap there is a struggle for existence Not enough for all so individuals must Competition Competition other When resources are scarce individuals must compete with each Those that win survive reproduce traits become more Those that lose do not survive do not reproduce traits become common less common As many more individuals of each species are born than can possibly survive and as consequently there is a frequently recurring struggle for existence it follows that any being if it vary however slightly in any manner profitable to itself under the complex and sometimes varying conditions of life will have a better chance of surviving and thus be naturally selected From the strong principle of inheritance any selected variety will tend to propagate its new and modified form On the Origin of Species Introduction What resources do organisms compete over Resource Competition Food Organisms must compete if they eat the same food Total amount of food limited by environment Droughts floods fires other organisms etc Human impacts Land development Clear cutting Mining Struggle Those that eat survive those that don t die Resource Competition Predation Animals hunt other animals for food Predator hunter Prey hunted Selection acts on both predator and prey Better hunters survive and reproduce Those best at avoiding being eaten survive and reproduce Resource Competition Territory Space in which to live Example barnacles Eat by filtering water Attach to a surface near moving water Must compete with other filter feeders for space Resource Competition Mating In sexually reproducing animals must compete for reproductive partners Examples Bighorn sheep ramming behaviors Peacock plumage Competition and Selection The many forms of competition that organisms face exerts a selection pressure We use pressure here as a metaphor Selection acts as a force that pushes the evolution of a species in a particular direction The more intense the competition the greater the selection pressure Individuals that are able to overcome these competitive restrictions to become reproductively successful are said to be fit Fitness Fitness The ability to successfully reproduce within a given competitive environment Organisms evolve to be best fit within their environment In other words fitness is relative http www youtube com watch v AMtT5 AQmLg Survival of the Fittest In truth natural selection does not choose the best traits it chooses the ones that are good enough to survive and be passed on In other words evolution is survival of the fit enough What happens to those species or individuals that are less fit They must change or die Traits and features of an organism that evolved in response to natural Adaptations increase the overall fitness of an organism in a given Adaptation Adaptation selection habitat Peppered Moths Peppered moth color Based on a single gene Many different alleles Native to England Vary between stark white and solid black Black moths rare until 1850 s Frequency near 100 after 1850 s Peppered Moths Lived on light colored trees light colors as camouflage 1850 s