HW from today s class due Wed Feb 12 at beginning of class Plant Evolution Origin of land plants 475 mya Origin of vascular plants 425 mya Origin of extant seed plants 305 mya Focusing on vasculature today Evolution change in the allele frequency of a population between generations List evolutionary mechanisms Natural selection Mutation Genetic drif Gene flow migration Land plants closely related grouped together Differences vascular tissue transport water quickly o Tracheids Thick strong walls grow taller to get closer to sunlight competition Nonvascular relies on osmosis and capillary action cohesion and adhesion o Like paper towel slowly taking up water Clicker Which mechanism consistenly leads to adaptive evolution A genetic drif B natural selection C Migration D mutation How did vascular plants evolve from non vascular plants Plants colonized land 475 mya no vascular tissues evolved yet 50 million years later 425 mya few inidivduals have produced cells that look like primitive tracheids Clicker How did tracheid like cells arise in a population of plants that originally did not possess them A Plants needed tracheid like cells to better adapt to dry land B random genetic mutation caused the formation of tracheid like cells in some individuals C plants that transport more water eventually develop tracheid like cells to assist them D Both A and B Mutations are actually random and not because it was needed also rare All else being equal plants with tracheid like cells would be better able to transport water In comparison to the original population would you expect the next generation to have A a greater proportion of individuals producing tracheid like cells B a smaller proportion of individuals producing tracheid like cells C an equal proportion of individuals producing tracheid like cells How did vascular plants evolve from non vascular plants There was a mutation in some individuals which led to genetic variation Phenotypic variation Interaction of phenotypes with environment Some phenotypes more likely to leave offspring than others More alleles passed to next generation change of allele frequency of next generation EVOLUTION Why tracheid like cells Some characteristics in common but not exactly the same They have continued to evolve to this day Very simple now they are very complex An organism has greater fitness than another if A it is stronger and therefore has greater chance of surviving to maturity B It can acquire more essential resources C It leaves more fertile offspring D It is better able to avoid predation Fitness End result of survival and reproduction Survival is important to reach reproductive age but producing offpsirng is very important Natural selection shows environment dependence Selects which has the better fitness Adaptations are ofen trade offs Ex Skunk cabbage releases lots of energy as heat 50 more than surroundings but not as much ATP germinates early and melts through snow One that releases lots of heat good for cold environments One that release less heat but more ATP good for warm environments Testing natural selection in diff environemtns Lets suppose we collected a few hundered individuals Transplant half to dry and half to moist Moist habitat Generation 1 95 Generation 2 91 74 Dry habitat Generation 1 95 Gen 2 of pop that doesn t orduce tracheid like cells of pop that do 5 9 26 95 produce tracheidlike cells Dry habitat Clicker Would you expect of population that do produce tracheid like cells to A increase B decrease C stay the same Organism with them would better transport water which is perfect for dry environments Moist habitat Clicker Would you expect of population that do produce tracheid like cells to A increase B decrease C stay the same Same reason for last question Could be detrimental by taking in too much water No benefit to having tracheids then they wouldn t have advantage but ones without it would be fine too so it could stay the same as well As long as you can provide evidence you can have a good answer During the evolution of vascular plants A each offspring had a lot more vasculature than its parents B each offspring had a little bit more vasculature than its parents C each offspring had roughly the same amount of vasculature as its parents Changes in populations frequency not offspring vs parents Example Tall x Tall mostly tall plants Short x short mostly short plants Tall x short lots of variation All tall plants are chopped off Short plants randomly mate mostly short with some variation Massive evolutionary change in just 2 generations huge evolutionary shif Key to evolution by natural selection Variation in heritable traits Successful individuals live to reproduce Less successful individuals have lower fitness How did present day vascular plants evolve from non vascular plants More cycling of bottom half of evolution flow chart Last step back to interaction of phenotypes with environment Cycled through whole flow chart back to interaction of phenotypes but for more xylem needs to be another mutation and cycle through evolution chart Why natural selection can t lead to perfect organism Adaptation are ofen trade offs o depends on environment o physical limitations based on adaptations taller plants become weaker Environments selective pressures change o Could be very close to being perfectly adapted but then the environment changes o Ex whole world covered in glaciers only 10 000 years ago Random chance also plays a part too many coincidences not likely HW Goal to demonstrate understaning of evolution by natural selection thru your ability to apply concept to a novel scenario Task describe how present day flowering plants produce complex flowers may have evolved through process of