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Study Guide - Midterm 2

by: Anastassia Erudaitius

Study Guide - Midterm 2 Econ 002

Anastassia Erudaitius

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This covers all lectures and most essential information since the first Midterm, and that is on the second Midterm
Intro to Macroeconomics
Craig McLaren
Study Guide
Economics, Macroeconomics, Econ 002, McLaren, UCR
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This 24 page Study Guide was uploaded by Anastassia Erudaitius on Monday February 29, 2016. The Study Guide belongs to Econ 002 at University of California Riverside taught by Craig McLaren in Winter 2016. Since its upload, it has received 36 views. For similar materials see Intro to Macroeconomics in Economcs at University of California Riverside.


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Date Created: 02/29/16
Macroeconomics – Econ 002 Midterm 2 Study Guide  Wealth = value of assets  Wealth effect: change in purchasing power o Purchasing power changes when:  prices change  Interest rate changes  Interest Rate Effect: change in price level  change in interest rate  change in quantity of AD o Price levels go up  interest rates go up  overall spending goes down (AD goes down)  International Trade Effect: change in domestic price  change in quantity demand for domestic goods o U.S. prices go up  demand for U.S. goods go down (and demand for foreign goods goes up)  NX falls  Changes that shift the AD curve: o Recessions shift the AD curve LEFT (prices fall) o spending of individuals and firms o Changes in real wealth o Changes in expected income o Changes in expected price levels o Stock market rises or falls o Change in real estate values o Expectations about future 1 o Change in consumer confidence o Foreign income and wealth  Foreign nation becomes wealthier  demand for U.S. goods increases (NX increases)  Foreign nation goes into recession  demand for U.S. goods decreases (NX decreases) o Changes in exchange rate (value of dollar)  Value of U.S. dollar rises  buys more foreign products, but less U.S. products bought by foreign nations  NX falls (this shifts the AD curve)  Value of U.S. dollar falls  U.S. doesn’t buy foreign products, but foreign nations buy much more U.S. products  NX increases (this shifts the AD curve)  Short Run Aggregate Supply o Time period where adjustments have not occurred yet o “sticky” input  causes ouput prices to be sticky  Contracts, menu costs, money illusion  Takes a while to change the prices and costs money to change prices  If general price level falls within economy but a restaurant does not adjust their prices (lower them) then customers will not come  quantity demanded falls o Low cost of changing menu prices  prices change more often o High cost of changing menu prices  prices change less often, and prices won’t adjust as quickly  SRAS Alternate Model o Capital and technology are fixed, capital/labor ratio is fixed o Firms will cut production when prices fall below break-even point 2  Keynes o Emotions affect economy o Economy does not gravitate towards smooth growth and high levels on employment o Economy could be stuck for years o Instability caused by lack of demand o Government must boost demand to restore economy to long-run equilibrium  Can boost AD by increasing G (government spending)  Consumers reluctant to increase C (consumerism) or I (ivestment) o Favors labor/consumers o Assumes economy approaches equilibrium dynamically o Markets may have significant recessions or inflations o Government spending DURING A RECESSION will increase demand and investment  Classical o Free market o No govt. intervention o Favors big business o Assumes economy is always at equilibrium o Markets are always at full employment o Taxing and spending only raises prices and debt o Picture shows: if you increase supply, you increase demand  Y= C + I + G + NX 3 o In order to raise AD when Consumer spending and Investments goes down, you must have a lot of government spending in response o Y= GDP, total output, total expenditure  Money Illusion: people mistake nominal values as real values o Workers won’t accept pay decreases (even if decrease is nominal)  results in sticky prices  firms will reduce output instead of cutting wages  Long-run shifts (Right – left shifts in LRAS) o Whenever the long-run AS curve shifts, it takes the short-run AS curve with it.  But short-run AS curve can shift on its own  Short-run shifts (up and down) o ONLY the short-run AS curve shifts:  Temporary supply shocks  Changes in expected future prices  Inflation o AD curve shifts right  Recession o AD curve shifts left o SRAS curve shifts down  Stagflation o SRAS curve shifts up o Presence of both inflation and recession  loss of faith in Keynesian Economics o Recession due to loss of supply NOT loss of demand  Reaganomics o Intended to increase supply not demand o Required massive borrowing overseas 4 o Peacetime deficit spending  1990s o Improvement in technology  more supply o Slow job growth Classical Keynesian Key Time Period Long Run Short Run Price Flexibility Prices flexible Prices sticky Savings Crucial to growth A drain on demand Key Side of Market Supply Demand Market Tendency Stability, full employment Instability, cyclical unemployment Government Intervention Not necessary Essential  Monetary policy: influencing the economy via money supply  Fiscal policy : influencing the economy via government spending and taxes o Congress and president approves taxes and spending o Can be used with monetary policy or alone o Economic stimulus Act  tax rebate to promote spending, stimulating economy o American Recovery and Reinvestment Act  government spending to increase AD  Disposable Income: sum of all incomes in economy after subtraction of taxes and addition of transfer payments o Real disposable income can be considered GDP o DI = GDP – taxes + transfers 5  MPC = Marginal Propensity to Consume ∆???????????????????????????????? o MPC = ∆???????????? o The portion of your income that you spend  Consumer Expenditure (C) = the total amount spent by consumers on newly produced goods or services o This does not include purchases of new homes because homes are considered investment goods  Consumption Function = total consumer expenditures vs. total disposable income ∆???????????????????????????????????????????? ∆???????????????????????????????? o MPC is slope  MPC = ∆???????????????????????????????????????? ???????????????????????? ∆???????????? o Intercept = autonomous spending: what you must spend to stay alive  function never passes through origin o There is a change in disposable income  movement ALONG the consumption function o Change in any variable that affects consumption  shifts the entire consumption function  Changes in future income expectations  Changes in wealth  Changes in price level  Changes in real interest rate  In a recession there is more output than there is spending o output exceeds spending → results in increase in inventory o so producers cut back → don’t make as much product o Continue to cut back until equilibrium is reached → spending = output  In an inflationary gap spending exceeds output o If spending exceeds output → you have an inventory reduction o production expands until equilibrium is reached 6  The Multiplier Effect o small shift in expenditure curve = large change in GDP o Multiplier = 1/(1-MPC)  Lower income countries have higher MPC than wealthier countries o higher income means your basic needs have been met o additional income is more likely to be saved for the future  Relationship to multiplier o If a “stimulus package” is introduced in the form of tax breaks with the goal to boost AD it will be more effective if it increases the income of people with a higher MPC  Reasons why government policy doesn’t always work to recover from recession o Time lag  GDP data released quarterly  Final estimate not known until 3 months afterwards  Unemployment data lags even more  Growth is not constant → one bad quarter or one good quarter doesn’t mean anything  Fiscal Policy fishtaill → results from time lag o Implementation lag  changes in taxes and spending must pass through both houses of congress and the president  often causes greater delay than monetary policy o Impact lag  just takes time to materialize  multiplier effects occur over time  Effects of time lags o risk of destabilization o expansionary policy may hit when the economy is already expanding o contractionary policy may hit when the economy is already shrinking o this could make cycles worse rather than smoothing them out!  Automatic stabilizers o government programs that naturally implement countercyclical fiscal policy in response to economic conditions 7 o Progressive income tax rates  tax bills fall when incomes fall (during recession) and rise when incomes rise (in expansion) o Corporate profit taxes  lower total tax bills when profits are lower, raise tax bills when profits are higher o Unemployment compensation  increases government spending automatically when the number of unemployed rise o Welfare programs  increase government spending during downturns and decrease government spending when the economy is doing better  Crowding Out o occurs when private spending falls in response to government spending o individuals may just let federal spending substitute for their own spending  if the government buys a good for you, you won’t have to buy it yourself  Ricardian Equivalence o money received by an individual today must be paid back later (possibly higher taxes) since it was paid for by government spending → but the individual expects that higher taxes will be coming so instead of spending the money they save it → increases in savings results in less increase in government spending  Supply-side fiscal policy initiatives o R&D tax credits: gives firms an incentive to spend resources on technological advancement o Education policies: subsidies or tax breaks for education (Pell Grants) create incentives to invest in education, increasing effective labor resources 8 o Lower marginal income tax rates: creates incentives for individuals to work harder and produce more, since they get to keep a larger share of their income o Marginal tax rates are placed on earnings ABOVE a minimum amount o Highest marginal rate is on earnings over $388,000 o Goal is to increase growth = increase output o One objection to supply-side tax cuts is that demand-side changes are larger than supply-side changes  Keynesians argue this  that supply-side tax cuts will increase demand-side effects, and in an inflationary gap the increase in demand would increase output but also increase prices raising inflation even more  The most volatile component of aggregate demand is investment spending  Price level changes have their greatest effect on consumers’ wealth  Investment spending is often the cause of business fluctuations in the US  The reason for the multiplier effect is that one person's additional expenditure creates a new source of income for another person and this additional income leads to still more spending  Money: o Unit of account, storable value, medium of exchange o Commodity Money = gold, silver, or highly tradeable goods o Fiat Money = paper money, backed by the economy itself  Created and destroyed in daily interactions  Divided into categories depending on how easily it can be exchanged o M1 = currency and checkable deposits o M2 (near money) = all of M1 + money market accounts + savings accounts  Fractional Reserve banking = banks keep a fraction of their deposits and lend out the rest  Of every deposit x a bank receives, it must keep a certain fraction x/r on reserve 9 ????−???? o It can then loan out the rest: ????  Reserves = what a bank must keep on hand  government bonds, ratio is same for all banks  Capital = “other” securities, ratio depends on type of bank  Money Multiplier = 1 = 1 ???????????????????????????? ???????????????????????????????? ???? 1  Change in money supply = ( ???? ???????????????????????????? ???????????????????????????? )  FDIC = insures deposits up to $250,000 o Regulates bank management o Enforces reserve requirements o Prohibits overly risky investment of depositor funds o Can close a bank for unsound practices o Prevents panic from depositors o Prevents moral hazard (on the part of bank managers)  taking a risk because you know someone will bail you out o If more people are withdrawing money than the bank can supply, the Fed loans the bank the needed reserves o FDIC insures bank deposits against the failure of an individual bank  The government banking regulation that places an upper limit on the money supply is reserve requirements on bank deposits  Monetary policies carried out by the Fed are sometimes inconsistent with fiscal policies  When the Fed wants to expand money supply through open market operations they will buy government securities from member banks  Banks make decisions based on what they THINK the economy will do o If there is a bad outlook  banks make fewer loans and raise reserves  Reduces the multiplier and the money supply  Can make loans harder to get and can lead to a recession 10 o If there is a good outlook  banks will make more loans, and lower the reserves  This increases the multiplier and the money supply  Can lead to inflation  Local banks keep their reserves on deposit at the Fed  the fed and other banks lend reserves to local banks as needed  the interest charged is “the Fed Funds (or discount) rate”  Board of Governors  appointed by the President (Public sector governance) o They appoint 3 directors to each Federal Reserve Banks (12 total) o Determine reserve requirements (part of the regulatory function)  reserve requirements on bank deposits (determines upper limit on money supply)  Member Commercial Banks (Private sector governance) o They elect 6 directors to each Federal Reserve Bank (12 total)  Chairman of Federal Reserve  Board of Governors AND FRBs o determine Federal Funds Rate (Discount Rate)  determines interest rates that banks can charge o determine monetary policy  raises or lowers the supply of investment, buys and sells government bonds o Federal Open Market Committee  open market operations  Wealth = sum of assets o Liquid assets = things that can be sold quickly  cash, bank deposits  Little or no interest o Non-liquid assets = things that take a while to unload  Long-term deposits, stocks, bonds, land, equipment, capital  Provides return on investment  Supply of Investment o Non-liquid assets = interest bearing assets o People sell their non-liquid assets to get money 11 o People buy non-liquid assets to save money o Supply of investment increases when return goes up  Stock prices  Bond prices  Interest rates  Demand of Investment o Borrowing: lender gets paid the agreed upon amount as long as the borrower is willing and able to pay o Selling stock: stockholder gets a dividend which is a portion of the company’s profits  Stocks initially sold to “primary market”  sale is arranged through investment bank, or sale is to households at a pre-determined price  Stocks are re-sold to the “secondary market”  sale is from household to household, price based upon performance expectations, may go up several- fold within hours, revenue from resale does not go to the issuer/company  Advantages: stockholder bears risk, not company (no dividends unless company profits)  Disadvantages are for the insurer: dilutes existing stockholder’s share of ownership/control  How to Raise Capital as a company o Getting a loan  Negotiated with single lender  Borrower pays back borrowed amount plus interest o Selling Bonds  IOU sold on open market  Equivalent to principal + interest  what company pays back  Investor pays less than the value of the IOU  they only pay principle  Bonds are issued at “par” value  the amount the issuer agrees to pay 12  Bonds sold at discount price (determined by supply and demand, determined by credit-worthiness of issuer) ???????????? ???????????????????? − ???????????????????????????????? ????????????????????????  ???????????????????????????????? ???????????????????? = ???????????????????????????????? ????????????????  Bond prices fall  Interest rates rise  This is because higher risk bonds sell for a lower price and pay at a higher interest  Bonds also sold to primary, and then secondary markets  Interests rates compensate lender for taking a risk  Loans  Higher risk = higher interest rate = lower price o Determined by rating agencies, govt. has max rating, govt bonds set the base rate for everyone else  Government Bonds o US Treasury sells bonds on open market (T-bills)  Supply is fixed (vertical line), demand is downward sloping (negative)  As supply of bonds increases, bond prices fall, and interest rates rise  Open Market activity o Fed = largest buyer and seller of govt bonds  Controls supply of T-bills and the T-bill interest rate o Transactions are made with bank reserves  Controls money supply  Controls Fed Fund Rate  Expansionary Policy o Goal is to increase AD o Can increase AD by raising Aggregate spending o Can raise aggregate spending by raising investment o Can raise investment by lowering interest o Can lower interest by reducing the supply of bonds 13 o Overall:  Reduce supply of bonds  Lower interest  more investment  more aggregate spending  more aggregate demand  Note: it is important to remember that for bonds prices of bonds and interest rates are opposite o Bond prices rise  interest rates fall o Bond prices fall  interest rates rise  Contractionary policy o Goal is to reduce AD o Increase supply of bonds  lower prices of bonds  higher interest rates  less investment  less aggregate spending  less AD  Where does the supply of funds in the loanable funds market come from? o Consumers saving their money in the financial system  consumers supply funds by saving and firms borrow that money (firms demand, consumers supply)  The real interest rate = the price of money  Equilibrium in the market for loanable funds: o Savings = investment o This is because savings of consumers = investment done from borrowers  Risky loans and Housing o Stated income, sub-prime o Teaser rates  required refinancing o Betting on rising real estate prices o Mortgages sold as Mortgage Backed Securities (bonds)  Mortgage brokers made commissions whether the loans were repaid or not  Rise of Housing prices o Supply of unsold housing is stable/fixed 14 o Exotic loans TEMPORARILY lower monthly payment for a given amount borrowed o This RAISES the price of a house a given buyer can afford (for the next couple years)  this RAISES DEMAND for housing  this INFLATES house process artificially  Collapse of housing prices o Speculators begin to default  and supply of housing rises  prices fall o Falling prices of housing means those who need to refinance cannot because the house is worth less than what they bought it for  so now they defaults  Collapse of Mortgage Backed Securities (bonds) o Once defaults became common the demand for these mortgage bonds collapsed (toxic assets)  Capital MUST be greater than 1% of assets o But should be greater than 7% of assets o If assets are greater than capital of the bank the bank is insolvent and the FDIC takes over  If capital of the banks disappears  lending stops  investment falls  expenditure falls  output falls  TARP – Troubled Asset Relief Program o Creates market for toxic assets (no one wants to buy them) o Fed-Congress loan capital to some banks that are too big to fail and Fed- Congress buys equity in some institutions  Monetarism – alternative to Keynesianism o Study AD by focusing on M and V rather than C,I,G,NX o Prices and output influenced by money supply  Govt intervention should be to print more money  However printing money only causes inflation  Thus monetarism is a very old stupid idea 15 o Velocity = number of times/yr that an “avg. dollar” is spent on goods and services o V= (Nominal GDP)(Money stock) o Equation of exchange: MV =PY o If V were constant than increase in M results in increase in GDP o Implies that Fed can control nominal GDP o In U.S. V is not constant o V determined by:  Efficiency of payment systems  speeds things up  Interest rates  High interest rates: decreases M but increases V  Low interest rates: increases M but decreases V  Monetarism Modernized o Used WHEN V is fairly constant o Rules: Fed should hold interest rates and growth of the money supply to established targets  Stable interest rates lets borrowers and lenders know what to expect  Keeps prices stable o Discretion: The Fed should manipulate interest rates and money supply to maintain full employment o However, when the demand for money is shifting, the Fed cannot control both money supply and interest rates  Passive Policy o Fiscal: No stimulus or tax cuts o Monetary: Fed holds interest rates OR money supply at predetermined targets  Active Policy o Fiscal: Yes on stimulus and tax cuts o Monetary: Expansionary or contractionary policy as needed to cure recession 16 o Argued to be used during times when economy has serious deficiency or excess of AD  Fiscal policy affects economy for quickly  Monetary policy can be IMPLEMENTED more quickly  Money Demand decreases  Interest rates fall during a recession,  Interest rise during an inflation 17 Vertebrate Anatomy – Biol 161A Lecture 13 – Evolution of Flight  Evolution of flight encouraged by : o Access to food  new niche, new source of food (similar to when amphibians invaded land) o Escape from predators  birds were first bipedal runners who developed gliding and then flying as an escape mechanism,  [or flight may have begun with arboreal gliders]  Advantages attained once flying evolved: o Access to non-food resources  cliffs, trees, islands for protected nesting spots o Efficient locomotion  long-distance migrations possible  Allows utilization of sparsely spread resources  Utilization of seasonal resources o Dispersal across barriers  oceans or mountains  Ex. Arctic Tern  migrates from North to South Pole  Note that these same advantages apply to those with erect gait and cursorial adaptations  The advantages for birds however are more extreme  long migrations, feeding over wide area  Flight in Reptiles (happened first) o Pterosaurs may have been first vertebrae to fly  Upper Triassic (220 myr) and persisted until end of Mesozoic (65 myr)  Ranged from small, sparrow sized to largest of all fliers (25-45ft wingspans)  No fossil record, unclear how they evolved flight  Fed mainly on fish (most fossils found in marine deposits)  While most fossils are found in marine environments it could be because fossils are much more likely to form there, and much less likely to form 1 in forest environments  pterosaurs could have been abundant predators in other environments as well but we lack the fossils to tell  Flight in Birds (happened second) o Strong evidence for dinosaur origin of birds  Birds derived from Maniraptorians o Archaeopteryx – oldest fossil record of bird  Debated whether or not it was capable of sustained flight o First birds that could certainly fly – 140 myr ago  But the adaptation to flight must have come earlier because at 140 myr the modifications of birds represent specialization for flight (Sinoris)  Flight in mammals (happened third) o Order Chiroptera o Bats made sudden appearance in early Cenozoic (50-60 myr)  Little fossil record, not sure how their flight evolved  What fliers and swimmers have in common o Both move through fluid medium and are subject to same types of drag o For birds  profile drag = friction drag + pressure drag  Fliers also have induced drag – caused by wing-tip vortex o Fusiform shape for birds  They have a fusiform shape because they have contour feathers along body contour  Their body itself is not actually fusiform  they can have this fusiform figure from feathers because air is a less dense medium than water  Long, flexible necks  but seem continuous with the body because of these contour feathers o Wings – of all classes (reptiles, mammals, birds)  Must have large surface area that can be flapped to generate lift and thrust 2  All of the wing structures in flying vertebrates involve modification of the forelimb  but each arrived at this modification in a different way  Therefore, bone elements in wing are convergent and homologous  Primary modification = elongation of forelimb  For all flying vertebrates the wing is a three-segmented forelimb with additional structures to enhance the surface area  First two segments  humerus and radius/ulna  Third segment  modification of wrist and hand bones o This third segment forms differently in each of the three groups  Can tell flying vertebrates apart by their digits/hands  Wings of birds involve ONLY THE FORELIMB  Wings of bats and pterosaurs involve the FORELIMB AND HINDLIMB  This is important because birds evolved more diversely ecologically because they had separate hindlimbs  hindlimbs can evolve independently  Birds may have feet specialized for running, swimming, or grabbing and dismembering prey  This type of diversity is not seen in bats or pterosaurs because the hindlimbs are necessary for flight o Trunk  In all cases the trunk is shortened, and stiffened  Stiffened by  enlarged series of sacral vertebrae, fusion of trunk vertebrae, broad ribs that may have overlapping processes  This places center of gravity near shoulder joint, where propulsive drive originates  Propulsive drive must be at center of gravity so that flapping does not make body summersault o Synsacrum- fusion of pelvic girdle, lumbar, sacral, caudal verte. o Note: Pygostyle- fused caudal vert. for feather attachment  Enlarged, keeled sternum for attachment of enlarged pectoral muscles 3  Well developed in birds and pterosaurs, not so much in bats  All have V shaped bones that brace the shoulder joints  but they evolved convergently and you can tell because . . .  Birds – have furcula (clavicles) and coracoids  Pterosaurs – only have coracoids  Bats – only have clavicles  Note: In terrestrial animals the center of gravity is placed over the hind limbs since they are the main source of force generation in locomotion  How birds fly o The air travels over a longer path on the top of the wing than under it  the air on top must therefore travel faster  this difference in velocities results in lower pressure above the wing and higher pressure below the wing creating a net push that lifts the bird o Induced drag – the mixing of air at different pressures at the tip of the wing o Birds wings are like an airfoil  2 ways to increase lift of airfoil:  Increase camber (make it more curved)  Angle it upwards (increase angle of attack)  the angle being between direction of motion and tilt of wing o Limits: power stall angle  the threshold where air above wing is no longer laminar but instead turbulent  at this angle the object will lose lift and altitude  In each case ^ enhanced lift occurs because of an increase in the path length the air must follow over the wing relative to under the wing o Lift is directly proportional to the surface area of the wing and speed 2 o Lift = v x S  v = speed  S = surface area o Slow flying birds  greater surface area of wings and/or greater camber 4  In respect to fast flying birds  Powered Flight o Power stroke and recovery stroke  Configuration of wing must be different for each o Power stroke – generates lift and forward propulsion  Wing is twisted so that leading edge tilts downward  Force of wing on air is perpendicular to wing  therefore the force vector points down and back  Lift component perpendicular to direction of movement of fluid over surface of wing  Thrust component perpendicular to lift o Recovery stroke – returns wing to starting point, maintains and generates lift  “hind-wing” – area covered by humerus and radius/ulna o Gliding surface  generates lift during power and recovery strokes o Remains horizontal during both strokes  “fore-wing” – area derived from carpals and digits o Propulsive surface  generates thrust o Horizontal during power stroke o Vertical during recovery stroke  Aspect ratio o Ratio of length to average width o High aspect ratio = long, narrow wing o Low aspect ratio = short, broad wing  Types of wings o Elliptical wing – (all purpose)  low to moderate aspect ratio (3-6) 5  high camber  High lift, slow to moderate speeds, good maneuverability, good for flapping flight (forest birds) o High speed flapping flight (hummingbirds) –  long, narrow,  (high aspect ratio, >10),  high % of wing consists of hand/drive region  Note that high flapping speed does not mean the animal is moving quickly o High speed gliding – (albatross, sheerwater) – b/c bird moves fast or flies in high speed wind –  long and tapering,  very high aspect ratio (12-20),  low camber  Hind wing long  Fore wing short  Reduction of influence of wing tip vortex o Low speed gliding –  long, broad  moderate aspect ratios  high camber  generate a lot of lift at low speeds  slotted wing tips (vultures)  enhance lift and reduce wing-tip vortex  Birds  power and recovery stroke mostly powered by ventrally located muscles o Power stroke – pectorals originate on outer edges of sternum and insert on humerus, membrane runs from furcular to coracoids o Recovery stroke – supracoracoideus muscle – ventrally located but lifts wing  pulley system runs through triosseum foramen  even though contractions occur on the ventral side of the bird the muscle moves the wing in the opposite direction 6  Triosseum foramen bordered by coracoid, clavicle, and scapula  MAIN ACTION of the supracoracoideus muscle is to rotate the forelimb, rather than elevate it  allows for folding of wings during recovery stroke  Pterosaurs had a similar recovery stroke  foramina in shoulder joint where tendon could pass from sternum to dorsal surface of humerus  Recovery stroke often passive  therefore good flyers can have a small supracoracoideus and thus a small sternum  However, note that those with a large supracoracoideus and sternum may not be good flyers (chickens) but instead have fast take-off and periodic flight  that is what requires powerful recovery stroke  White meat in flight muscles of chicken  anaerobic activity  fast take-offs  Dark meat in flight muscles of ducks  high myoglobin content  continuous, aerobic activity  In some species the recovery stroke is partly powered by elastic recoil in the furcula o Power stroke causes furcular to bow, energy gets stored in downstroke, furcula springs back during recovery stroke and returns some of this energy, helping to lift wings  Bats  power stroke muscles on ventral side and recovery stroke muscles on dorsal side o Sternum much less keeled than birds because it is not an attachment point for muscles associated with BOTH power and recovery stroke (like it is for birds) o Enlarged area of attachment for pectoral muscles (different from birds)  muscles meet at sheet of connective tissue that separates left and right halves that tug at each other when they contract  Skeletons of birds o Hollow, long bones of wing o Lattice-work of internal struts (trabeculae) that give resistance to bending stress o However, total weight of bird skeleton is same as mammal of same size 7


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All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.