Biosc&0150:&Foundations&of&Biology&I.& & Review&11:&Chapter&44& &Adel,&Anthony,&Megan,&Dr.&Swigonova& & Page&1&of&16&Review&Chapter&44:&Gas&Exchange&and&Circulation&&1. At&the&Death&Valley,&Nevada,&the&atmosp he ric&pres su re&is&1&atm&(760&mmHg)&and&the&air&contains&21%&oxygen.&At&the&top&of&Mt.&E v er es t,&the&atmospheric&pressure&is&250&mm&Hg.&a. Calculate&the&PO2&at&the&Death&Valley&and&top&of&Mt.&Everest.&&Death&Valley:&0.21*760&=&160&mm&Hg&Mt.&Everest:&0.21*250&mm&=&53&mm&Hg&&&b. How&much&faster&would&you&have&to&breathe&at&the&top&of&Mt.&Everest&to&obtain&the&same&amount&of&oxygen&as&you&have&in&the&Death&Valley?&About&3&times&faster.&&c. Draw&a&graph&that&depicts&the&relationship&between&the&partial&p re ss ur e&o f &ox yg e n &and&elevation.&&&&&&&&&&&&&&&& &d. Why&do&people&wear&oxygen&masks&at&the&top&of&Mt.&Everest?&How&does&it&relate&to&Fick’s&law&of&diffusion?&Because&the&partial&pressure&of&oxygen&is&low&—meaning&the&diffusion&gradient&between&the&atmosphere&and&your&lung&tissues&is &small.&This&results&in&low&rate&of&diffusion&of&oxygen&at&the&alveoli&(P2ZP1&is&low,&thus&rate&of&diffusion&is&low).&&e. Can&people&climbing&Mt.&Everest&acclimatize&to&the&conditions?&People&usually&take&breaks&during&their&climb&to&acclimatize.&Only&partial&acclimatization&is&possible&and&it&depends&on&the&physical&state,&tra i n ing,&and&genetics&of&people.&Most&people&have&to&use&supplementary&oxygen&sources.&&2. To&obtain&oxygen,&water&breathers&face&a&much&more&challenging&environment&than&air&breathers&do.&Why?&Aquatic&animals&live&in&an&environment&that&contains&much&less&oxygen&than&that&of&terrestrial&animals&a. Do&freshwater&or&marine&environments&contain&more&oxygen?&Why?&Freshwater&environments&contain&more&oxygen&because&they&have&lower&concentration&of&solutes.&Because&seawater&has&a&much&higher&concentration&of&solutes,&it&can&hold&less&dissolved&gas.&b. Fish&in&deep&body&of&water&have&to&take&in&twice&as&much&water&as&do&fish&in&a&shallow&pond&to&get&the&same&amount&of&oxy gen .&W hat&co u ld&ac cou n t&for&this? &Surface&area&has&a&large&impact&on&oxygen’s&abi li ty&t o&d if fu se &in t o&w a t er .&T he &s ha ll o w &po n d &ha s&a &h ig h e r&ra ti o &of &surface&area&to&volume,&and&therefore&would&be&more&oxygen&rich.&This&would&mean&the&fish&in&the&shallow&pond&wo uld &no t&hav e&to&w o rk&as&ha rd&to &ob tain &the&n eed ed &oxy gen .&Biosc&0150:&Foundations&of&Biology&I.& & Review&11:&Chapter&44& &Adel,&Anthony,&Megan,&Dr.&Swigonova& & Page&2&of&16&c. Draw&a&graph&relating&temperature&and&gas&solu bility .& & &d. Explain&why&oxygen&partial&pressures&are&relatively&high&in&mountain&streams&and&relatively&low&at&the&ocean&bottom.& Oxygen&partial&pressure&is&high&in&mountain&streams&because&the&water&is&cold,&mixes&constantly,&and&has&a&high&surface&area&(due&to&white&water).&Oxygen&partial&pressure&is&low&at&the&ocean&bottom&because&the&area&is&far&from&the&surface&where&gas&exchange&occurs&and&there&is&relatively&little&mixing.&&&3. Rate&of&Diffusion&=&k&*&A&*&(P2ZP1)/D&a. What&do&all&of&the&variables&stand&for?&K&is&the&diffusion&constant,&A&is&the&area&for&gas&exchange,&P2CP1&is&the&difference&in&partial&pressure&o f&gas&o n&eith er&sid e&o f&the&ba rrier&to&diffusion,&and&D&is&the&thickness&of&the&barrie r&t o&d if fu si on &b. If&A&increases,&what&h ap p e ns &to &th e &ra te &o f&d iff u sio n ?&If &P2CP1&increases?&If&D&inc re a se s? &Increasing&A&=&Incre a sin g &ra te &o f&d if fu si on ;&in c re as in g &P2CP1&=&increasing&rate &of &di ff us io n;&increasing&D&=&decre as in g&ra t e&o f&d i ffu si o n&c. How&are&high&partialZpressure&gradients&maintained?&They&are&maintained&in&part&by&having&am&efficient&circulatory&system&in&close&contact&with&the&gasZexchange&surface&&4. Gills&can&be&external&or&internal.&What&are&the&advantages&and&disadvantages&of&external&versus&internal&gills&in&terms&of&fitness?&External&gills&are&ventilated&passively&and&are&efficient&because&they&are&in&direct&contact&with&water.&However,&they&are&exposed&to&predators&and&mechanical&damage.&Internal&gills&are&protected ,&bu t&h a ve&t o &be &ven tila te d &by &so m e&t yp e&o f&a ct ive&mechanism&for&wate r&flow.&a. Explain&why&countercurrent&exchange&is&much&more&efficient&than&concurrent&exchange.&In&countercurrent&systems,&oxygen&is&transferred&along&the&entire&length&of&the&capillaries.&If&concurrent&flow&occurred,&oxygen&transfer&would&stop&because&the&partialZpressure&gradient&driving&diffusion&would&fall&to&0&partway&along&the&capillary.&Put&another&way:&Countercurrent&flow&is&so&efficient&because&it&ensures&that&a&difference&in &oxy gen &partia l&pressure&in&water&versus&blood&is&maintained&over&the&entire&gasZexchange&surface.&b. What&part&of&Fick’s&law&of&diffusion&does&countercurrent&exchange&maximize?&The&effect&of&countercurrent&exchange&is&to&m axim ize &the&P2CP1&term.&&&5. Compare&and&contrast&the&problems&associated&with&gas&exchange&for&aquatic&and&terrestrial&animals.&(More&specifically,&compare&and&contrast&the&challenges&each&face&in&terms&of&maintaining&proper&homeostasis.)&For&aquatic&animals,&gas&exchange&disrupts&water&and&electrolyte&balance.&Recall&that&freshwater&and&saltwater&fish&both&face&challenges&in&terms&of&salt&exchange&and&water&Biosc&0150:&Foundations&of&Biology&I.& & Review&11:&Chapter&44& &Adel,&Anthony,&Megan,&Dr.&Swigonova& & Page&3&of&16&exchange&with&their&environment.&In&this&way,&aquatic&animals&need&and&active&osmoregulatory&system&that&maintains&both&electrolyte&and&water&balance.&ZZZZTerrestrial&animals&are&different,&however,&because&all&they&have&to&worry&about&is&water&loss&to&their&environment.&&They&do&not&lose&solutes&to&the&air&that&they&breathe&in&their&respiratory&syste m .&&6. Suppose&that&a&new&pesticide&has&proven&to&be&very&effective&in&keeping&farmers’&crops&from&being&destroyed&by&insects.&This&pesticide’s&mode&of&action&involves&dehydrating&target&insects,&leaving&them&incapable&of&preventing&water&loss.&In&terms&of&insect&anatomy,&explain&how&you&think&this&pesticide&works.&The&pesticide&could&cause&the&insect’s&spiracles&to&be&forced&open&continuously,&leaving&the&tracheal&system&con stan tly&exp o sed &to&th e&drier&o uts ide &air.&Th is&lead s&to&w ater&loss&and&eventual&insect&death.&Also,&it&could&dissolve&the&insect’s&cuticle,&leaving&it&unable&to&prevent&water&evaporation&from&its&body&surface.&&7.