Lecture 18 Outline of Last Lecture II. Action Potential III. Synapses Outline of Current Lecture II. Ancestral and Derived Traits III. Plants IV. Animals and Homeostasis V. Action Potential and Nernst Potential Current Lecture Bio 152 Exam 2 Review !Extra Credit assignment do before reading assignment!! see link on Moodle NO quiz this week reading assignment posted for week after spring break !!Ancestral and derived traits -the “blue” traits exist for all the organisms that are above it in the diagram -if the trait occurs in group under consideration and not ancestors, then it is derived derived trait defines a certain group more or less ex: reptiles + birds — digits is an ancestral trait because it exists in other taxa as well and ancestors !Considering primates, is the placenta ancestral or derived? -Ancestral (placenta also exists in cows and whales) and in ancestors -forward facing eyes for example would be derived (not on graph but Considering mammals is the placenta ancestral or derived? -Derived - there are mammals that lack this trait (the marsupials) but this is a defining feature of mammals (in general) !Plants Sources and sinks = how phloem works through positive pressure - sugar loaded at the source (high sugar, low sugar at sink) Bio 152 1st Edition!!!These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. !Edited with the trial version of Foxit Advanced PDF EditorTo remove this notice, visit:www.foxitsoftware.com/shopping! - this draws water into the phloem — cells are inextensible so the water and sugar are pushed to a cell that is unloading sugar A ripening fruit is probably a (not photosynthesizing or making sugar, it is drawing sugar from the plant) - sink Sugar maple in early spring - roots (no leaves on maple trees that are making sugar, so they’re a sink right now and they have to get sugar from somewhere) - if there were leaves you couldn’t get syrup from maple trees !Sporophyte = whole plant (and is 2n) -within flowers, meiosis will occur — produce 1n structures (pollen, and in the carpal will be the female gametophyte) -pollen has 3 cells — 2 of them are sperm cells and 1 vegetative nucleus -female gametophyte has 8 cells (all of which are 1n) — including the egg cell and 2 other nuclei (this is why the egg cell isn’t the female gametophtye, because that is the sac that holds those 8 cells — the ovule produces this structure) -so 2 sperm cells come in, one fuses with the egg and one fuses with the 2 other nuclei = DOUBLE FERTILIZATION (forming both the embryo and the endosperm) !Animals and Homeostasis pan on stove: -conduction is heating the pan through direct contact pan in oven = radiation, electric coil at bottom radiates heat to pan fan on pot would be convection evaporation is making heat go from liquid to gas !If I take a hot brick and a cold brick and put them beside one another what kind of transfer happens? -heat goes from hot brick to cold brick Jackrabbit with body temp of 37 C goes and stands out in the sun on a 45 degree day. Will heat leave his ears to the hot air? -No — it prevents external heat from coming in -you can’t stick your hand in hot water to cool it off -if it’s cooler outside than it is in the organism, then heat will move to atmosphere elephant flaps its ears using convective heat but this won’t work well if it’s much hotter than the elephants body temperature !Snake incubating her eggs. She wants them to stay one temp. She is an ectotherm but can still generate heat metabolically. Which part shows cold and which hot? -more contractions when it’s cold !Negative Feedback Loop for homeostasis -always neg feedback because it’s trying to counteract what it sees!-temp goes up and down a little bit — temp goes up a little bit so it shuts off radiation, it goes down and it starts the radiation again -same is true in the body !Would ectotherms body temp look like this? No because an ectotherm is adjusting its temp behaviorally, it doesn’t have a quick up and downs, they don’t have a set point like endotherms (hypothal doesn’t control temp like that) they do have an ideal temp but it depends on time of day !Why are ectotherms below the line? -because they don’t use metabolic energy to keep warm !!Action Potential and Nernst Potential Differentiate Nernst and membrane -Nernst potential is a voltage that will hold a given concentration of an ion across the membrane -can change it by changing the concentration (or changing the voltage because that will change the concentration) - as long as membrane is voltage -membrane potential = influenced by all the ions and all their permeabilities -resting membrane potential = relatively stable membrane potential in any given cell -action potential = a rapid change in resting membrane potential after reaching a threshold level it depolarizes !If a cell normally has an extra cell. concentration of 100 mM na and intracellular concentration of 10 mM Na what would happen to Nernst potential if you raise concentration of external to 500 mM? -the Nernst potential would become more positive -you’re increasing the membrane gradient which will make it more “like it is” so if it’s already positive it will just make it more positive by increasing the difference even more in the same direction -sodium high outside and low inside = positive membrane potential -concerns ONE ION !Neurons usually have high Na+ out and low Na — if you raise permeability what will happen? -would be more positive — when you make it more permeable it will go toward that ion nernst potential (so it will move towards the sodium nernst potential) - so if it’s negative inside the cell/ !Think about what happens for nernst potential to potassium - going to be E = 62mVlog(100/100) — you don’t need a voltage because it has already come to equilibrium, - because membrane is mostly permeable to K, it would want to go to potassium Nernst potential - must take sodium ions into consideration so it would go towards zero?! - so it would become more positive