Ependymal cells Cilia on one surface Movement of material or fluid over surface of the cell

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1 2004 Bology GA 1: Wrtten examnaton 1 SPECIFIC INFMATION Secton A Multple-choce Ths table ndcates the approxmate percentage of students choosng each dstractor. The correct answer s the shaded alternatve. Questo n A B C D A B C D % Queston % Queston 7 The mcroorgansms are found lvng n sprngs of bolng water. The enzyme actvty of these mcroorgansms s therefore most lkely at an optmum when the temperature s at 100 o C. 37 o C s the optmal temperature for enzyme actvty n humans. Queston 18 Desgn 1 exposes the same 12 ducks to four dfferent drnkng waters durng the course of the experment. Desgn 2 exposes only three ducks to each dfferent drnkng water. There wll be some varaton between ndvdual ducks whch may nfluence the results obtaned from an experment set up along the lnes of desgn 2. Secton B Short Answer For each queston a correct answer (or answers) s provded. In some cases the answer provded s not the only answer that could have been awarded marks. Queston 1 Marks Average % Cell Type Structure/ Cell Characterstc Functon Neuron Thn processes extendng from cell body Transmsson of nerve mpulses Mcrogla flexble cell membrane capable of movement to engulf materal outsde the cell Phagocytoss Ependymal cells Cla on one surface Movement of materal or flud over surface of the cell Many students could correctly dentfy the functon of the thn processes extendng from the cell body as a neuron. Students may not have been famlar wth ependymal cells or mcrogla but should have knowledge of phagocytotc cells and the functon that cla has on cells. Some students ncorrectly stated that cla ncrease the surface area for absorpton of materals nto a cell. Bology GA 1 Exam 1 VCAA 2004 Assessment Report 1

2 % Beaker A (10% glucose at 30 o C) Reason water moves along a concentraton gradent from hgh concentraton of water to a low concentraton of water AND water therefore would move from nsde the cell across the membrane to the 10% glucose soluton (that s, ether beaker A or B) AND Movement of molecules s greater at hgher temperatures therefore there s a greater movement at 30 C than 1 C. Therefore the celery n beaker A would show greatest loss of mass. Many students could correctly dentfy the pece of celery that would show the greatest loss n mass after 30 mnutes. Most students could descrbe the movement of water along a concentraton gradent but very few students could clearly reason why the ncrease n temperature ncreased the water loss. Some students ncorrectly related the ncrease n temperature wth enzyme actvty. Students need to remember that osmoss s a passve process. Queston 2 % The growth hormone (auxn) s produced n the tp of coleoptles. Although group 2 coleoptles were cut, the tp remaned and auxn was avalable to dffuse down the stem and stmulate growth. In group 3, the removal of tps meant no auxn was avalable and hence no growth. Students are remnded to carefully read the stem of the queston. Some students referred to lght receptors n ther answers. The stem of the queston states that the coleoptles were ncubated for four hours n darkness. % Coleoptle juces n agar contan a growth hormone (auxn) that dffuses from the agar nto group 5 coleoptles whereas the agar on group 6 coleoptles contans no juces therefore no hormone to stmulate growth. When a queston requests a comparson be made between two groups the response should make menton of both groups. Student responses such as group 5 coleoptles have auxn could not be awarded a mark as no menton of what happened to group 6 was made. Some students ncorrectly referred to the presence of nutrents n the juce as the cause of the growth. % Predcted growth result No growth Vertcal growth Bendng to left Bendng to rght Expermental Group The most common mstakes made by students when fllng n ths table were predctng the growth result for groups 8 and 9. Many ncorrectly stated that group 8 would bend to the left and group 9 to the rght. Bology GA 1 Exam 1 VCAA 2004 Assessment Report 2

3 Queston 3 % They regrow but not back to ther orgnal length. Readng data from a graph s an mportant skll. The stem of the queston states from the data shown n the graph and students should refer drectly to the graph. Better students made reference to the actual length of the flagella n ther responses. An example of a good response would be the flagella grow back to an average length of 9.5µm, about 1 µm smaller than ther orgnal length. % Lens C. Flagella are just over 10 µm long. A feld of vew wth 75 µm dameter would allow for greater magnfcaton of the flagella whch means much greater accuracy than havng to measure 10 µm n a feld of 450 or 1800 µm dameter. Many students dd not know that a smaller feld of vew equated to a hgher magnfcaton of the flagell The hgher magnfcaton made t easer to measure the flagella that were only 10 µm long. Another lens would have been used f the flagella had been longer than 75 µm as the flagella would not ft nto one feld of vew. % A cell wall of a typcal plant cell s made of cellulose, not glycoproten. d. % Golg complex Golg body Golg apparatus. Organelles that package and store materal nto vescles for export from the cell. e. % Oxygen. f. % Adenosne trphosphate or ATP. g. % Presence or absence of oxygen.. When oxygen s present, the amount of ATP produced per molecule of glucose s about eghteen tmes the amount produced when there s no oxygen. When oxygen s present, there s 36 ATP (or 38 ATP) produced per molecule of glucose compared wth only 2ATP n the absence of oxygen. Bology GA 1 Exam 1 VCAA 2004 Assessment Report 3

4 Queston 4 a Marks Average % decrease n concentraton of blood calcum Blood calcum concentraton 2.2 to 2.5 mmol/l Increase n concentraton of blood calcum parathyrod gland cells n thyrod release release parathyrod hormone calctonn acts on acts on bone cells called osteoclasts bone causng results n breakdown of bone and releasng calcum nto the blood ncreases amount of calcum deposted nto bone Increase n concentraton of blood calcum Blood calcum concentraton 2.2 to 2.5 mmol/l Decrease n concentraton of blood calcum Students should be famlar wth flowcharts llustratng feedback mechansms. Although students may not be famlar wth the mechansms controllng human blood calcum concentratons all relevant nformaton was ncluded n the paragraphs precedng the queston and could be used to fll n the empty boxes n the flowchart gven n the queston. % Receptors or chemoreceptors. % Control mechansm n homeostass n whch the state of a varable s montored to see f t changes and f a change s detected, a response s trggered to reverse the drecton of the change. Control mechansm n homeostass n whch a change n a stmulus s detected and a response s trggered that decreases the stmulus. Few students could clearly express ths concept. The queston was worth two marks and students needed to make two dstnct ponts to be awarded full marks. Bology GA 1 Exam 1 VCAA 2004 Assessment Report 4

5 Queston 5 % Oxygen s used n cellular respraton to produce ATP whch drves metabolc reactons n cells. Many students wrote the greater the ntake of oxygen the hgher the metabolc rate. Ths response was not awarded a mark as t does not explan how oxygen s used to drve the metabolc rate of the anmals. % From 15 C to 25 C Students were expected to state correct unts n ther answer. Answers of 15 to 25 were not awarded a mark. The unt for temperature s gven on the horzontal axs of the graph and students should be able to copy the unt exactly as t s wrtten on the graph. Marks Average % Curlng up reduces the surface area exposed and therefore reduces the area from whch heat may be lost A lower surface area to volume rato means less heat per unt volume s lost by the anmal. The contnued contracton of muscles durng shverng generates heat for the anmal the metabolc actvty nvolved n the muscle contracton of shverng generates heat for the anmal. Dlaton of blood vessels allows a greater volume of blood to flow close to the surface and a greater surface area across whch heat can be lost. The spreadng of salva allows surface heat of the anmal to be used n evaporaton of the salv Both observatons relate to ncreased loss of heat from the anmal. d. % Water produced by metabolc actvtes n the anmals tssues. Incorrect responses gven by students related to the envronment that the sprnghare s naturally found, for example obtanng water from leaves of plants. Students are remnded to read the nformaton gven n a queston and take t nto account when formulatng ther answers. e. % Lower temperature means a lower metabolc rate and hence less heat produced by metabolc actvtes. Therefore less requrement for water loss to control body temperature Ar more humd nsde the burrow so reduced evaporaton of water from surface of the sprnghare. Therefore less water loss Durng the hotter part of the day the temperature n the burrow s lower than the outsde temperature and there wll be a lower evaporaton rate of water from exposed surfaces. Therefore less requrement for water loss to control body temperature. Bology GA 1 Exam 1 VCAA 2004 Assessment Report 5

6 Queston 6 % Insuln. Insuln acts on cells so that the cells ncrease ther uptake of glucose from the blood. Insuln acts on cell membranes so that the cells ncrease ther uptake of glucose from the blood and stmulates lver cells to convert glucose nto glycogen. Many students correctly dentfed the hormone as nsuln. Responses such as nsuln reduces blood sugar levels wthout any further explanaton were not awarded marks. % An ncrease n the concentraton of glucose n the blood. % Two ponts were requred n the answer to ths queston. The pump would be able to delver the nsuln at frequent ntervals and so less hormone would be requred at each delvery. Wth hormone njectons, larger volumes of the hormone would be delvered at each njecton. AND Peaks and troughs of amount of hormone present would be greater wth the njectons, hence greater varaton n blood glucose. The peaks of glucose would be hgher wth njectons and the lows of glucose would be lower. Queston 7 % The dead or attenuated cells are stll dentfed as foregn and retan antgenc property to stmulate the producton of antbodes aganst t when njected. % Two ponts were requred n the answer. After vaccnaton, the antgens combne wth some of the B cells n the ndvdual recevng the vaccnaton and cause the B cells to reproduce rapdly resultng n large numbers of cloned cells (that s clonal expanson). AND Many of these cloned cells form plasma cells but some form B memory cells whch can survve for many years, sometmes for lfe and react mmedately to produce antbodes f the person s renfected wth the partcular antgen. The concept of clonal expanson was poorly understood by many students. Some students ncorrectly stated that plasma cells gve rse to memory cells. Bology GA 1 Exam 1 VCAA 2004 Assessment Report 6

7 % Antbodes n a newborn baby wll have crossed the placenta from the mother durng fetal development. After brth, a baby can obtan antbodes from a mother s mlk f they are breast fed. d. Marks Average % The correct graph s shown above. Marks were awarded to graphs wth the followng three features three njectons therefore three peaks, each hgher than the prevous AND response tme shortens after each njecton gradent of graph ncreases AND after fnal njecton, very slow reducton n antbody producton. Many students drew a graph showng three peaks n antbody levels and a slow reducton n antbody level after the last njecton. Some students dd not complete the graph, stoppng at about 12 months nstead of contnung on untl 18 months. Fewer students could show ether the shorter response tme after each njecton or the more rapd producton of antbodes after each njecton. Queston 8 % Mtoss % Any two of the followng features: Presence of hooks Able to attach wthn tssues at approprate places and not be swept away by blood or other fluds. Flattened structure large SA to volume rato Facltates absorpton of oxygen and food. Flagella or cla Asssts movement when n the blood. Thck outer layer Resst dgeston by enzymes. Some students mentoned features that related to the survval of the speces and were not awarded marks. Producng large numbers of eggs was an example of such an ncorrect response. Other students gave features of the host that made t sutable for the blood fluke to survve. To be awarded marks the feature had to belong to the blood fluke. Bology GA 1 Exam 1 VCAA 2004 Assessment Report 7

8 % Tcks lve n an ever changng envronment. A fluke lves n an nternal envronment that s constant n many respects, for example temperature. A tck burrows through the outer layers of har or fur and btes nto and attaches to the underlyng skn to ensure a reasonably constant temperature. Fluke lves n envronment n whch food s constantly avalable and obtans readly by absorpton across ts outer layers. External paraste such as a tck must seek out ts host. A tck burrows and btes nto and attaches to the underlyng skn to ensure they take n as much food as possble. A tck releases ts hold and drops off only after t has gorged an mmense amount of food compared to ts sze. Tck has to cope wth loss of water to the envronment compared wth fluke that lves n a constantly most envronment. A tck has a hard external skeleton (exoskeleton) to assst n preventng dehydraton Tck runs rsk of beng scratched off by the host anmal f they cause tchng. Produce chemcals to nhbt nflammaton response. d. % Vruses need to enter lvng cells for ther reproductve cycle. On maturty of the vruses wthn a cell, the cell bursts open, vruses are released and then the cycle s repeated. Every tme vruses burst from cells there s a sudden ncrease n the number of vruses. When the vrus s nsde the cells the graph s level, runnng parallel to the horzontal axs. AND In contrast, bactera enter a host but are not dependent on any cycle wthn cells for ther reproducton. They show a sngle ongong phase of exponental growth ndcated n graph X. Many students understood that a vrus must enter a cell before t can reproduce. Few could relate the shape of the graph to the ncrease n number of vruses after nfecton. Bology GA 1 Exam 1 VCAA 2004 Assessment Report 8