B2a answers B2 A DISCOVER MARTIAN LIVING! Page 70 Cells. Page 70 Specialised Cells. Page 71 Diffusion 1. Page 71 Diffusion 2

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1 B2 A DISCOVER MARTIAN LIVING! B2a answers Page 70 Cells 1 a B hloroplast; C nuleus (1) A ontrols what enters and leaves the ell; D holds the ell in shape (1) Riosomes where proteins are made (1); mitohondria where (aeroi) respiration takes plae (1) Page 70 Speialised Cells 2 a Sweep muus (ontaining trapped ateria and dirt) up from the lungs (1) They have ilia whih an move in unison (1); they have many mitohondria to provide energy for the movement of the ilia (1) 3 a To asor water and mineral ions from the soil (1) They have a large surfae area (1) (Any 2:) Smaller; no large vauole; no hloroplasts Page 71 Diffusion 1 1 a Diffusion is the spreading of the partiles / moleules of a gas, or of any sustane in solution. This results in a net movement from a region where they are in a higher onentration. (4) Partiles are moving faster; have more kineti energy so they spread out faster (1); ump into eah other more often (1) 2 a Mitohondria (1) Rememer: Chek whih grade you are working at. Respiration happens faster / oxygen used up more rapidly resulting in a lower onentration of oxygen in the ell (1); so there is a greater onentration gradient (etween the ell and outside) (1) Blood oming to lungs is low in oxygen and high in aron dioxide so oxygen diffuses from high onentration in alveoli to low onentration in lood aron dioxide diffuses from high onentration in lood to low onentration in alveoli (2) Page 71 Diffusion 2 3 a Caron dioxide (1) Caron dioxide is used in photosynthesis (1); so there is a lower onentration inside the leaf than in the air / there is a onentration gradient from the air to the leaf (1) (Any 2:) Photosynthesis will take plae faster; so onentration of aron dioxide in the leaf will e lower; so diffusion into the leaf will e faster 1

2 B2 A DISCOVER MARTIAN LIVING! B2a answers Page 72 Osmosis 1 1 Osmosis is the diffusion of water from a dilute to a more onentrated solution, through a partially permeale memrane. (4) 2 a (Any 3:) Water moleules an go through the memrane; sugar moleules are too large to go through; water moleules diffuse / move y osmosis from the more dilute solution to the onentrated one; idea of random movement Heat the liquids (1); inrease the onentration of the sugar solution (1) Page 72 Osmosis 2 3 a It will urst (2) The strong ell wall stops it ursting (2) (Any 3:) It has een put in onentrated sugar solution; it has lost water; y osmosis; eause the ytoplasm is a less onentrated solution than the sugar solution; ontents have shrink and pulled away from the ell wall Page 73 Photosynthesis 1 a Caron dioxide + water gluose + oxygen (2) (Any 2:) Asors energy from light; the energy is used to make gluose; from aron dioxide and water Starh, energy store (1); ellulose, to make ell walls surose (1); to transport to other parts of the plant (1); proteins, for growth fats, as food stores in seeds (1) Page 73 Leaves 2 a i Near the upper surfae so light an easily reah them / so they get a lot of light (2) ii Cell in epidermis (either upper or lower) (1) (Any 2:) Starh is insolule; it annot get out of the ell; it will not interfere with reations in the ell; it will not affet the onentration of the ell and so will not affet osmosis 2

3 B2 A DISCOVER MARTIAN LIVING! B2a answers Page 74 Limiting fators 1 a 32.0 (1) The numer of ules given off per minute (1) d e (Any 2:) The numer of ules inreases with eah reading; suggesting the plant was still responding to the inrease in light intensity; she should have waited until the plant was photosynthesising steadily (Any 2:) Yes; the more light the plant is given, the faster it photosynthesises; suggesting that lak of light was stopping it from photosynthesising faster; however, at the highest light intensities the rate of photosynthesis seems to e levelling off; suggesting some other fator is eginning to e the limiting fator (Any 2:) The numer of ules might rise (ut not so muh as efore) or it might stay the same; light will no longer e a limiting fator; some other fator will limit the rate of photosynthesis; for example aron dioxide onentration 2 Caron dioxide produed whih inreases rate of photosynthesis (1); heat produed whih raises temperature and inreases rate of photosynthesis (1) Page 74 Healthy plants 3 a Plants otain mineral ions from the soil. They need nitrate ions for produing amino aids, whih are then used to form proteins. They need magnesium ions for making hlorophyll (4) i (Any 2:) The soil was short of nitrate ions; so giving the plant more allowed it to make more amino aids; whih ould then e used to make proteins; some of whih would e used to help the grain to grow ii (Any 2:) This ould have inreased the onentration in the soil; so it eame greater than in the plants roots; so that they lost water y osmosis; the plants eame short of water and ould not grow well Page 75 Food hains 1 a As hemial potential energy (in food) (1) (Any 2:) Some light does not hit their leaves; some light passes straight through the leaves; some light is refleted from the leaves; hlorophyll does not asor all wavelengths (olours) of light i Chloroplast (1) ii 200 units (1) 2 (Any 2:) Gluose roken down y respiration; to provide heat energy (to keep warm); this is lost to the environment; so there is less energy for the next organism in the hain Page 75 Biomass 3 a From ottom up: produers; primary onsumers / herivores; seondary onsumers / arnivores; tertiary onsumers / top arnivores (1) i (see diagram) (1) ii Energy is lost etween eah trophi level as heat / in respiration / other way in whih it is lost (1); so there is less energy availale for animals at suessive trophi levels so fewer animals an e supported at suessive levels (1) 3

4 B2 A DISCOVER MARTIAN LIVING! B2a answers Page 76 Food prodution 1 (Any 2:) The hikens do not need to produe heat in their odies; whih involves respiration; and uses up food so more of their food eomes hiken meat 2 (Any 4:) The shorter the food hain the less energy is lost; eing vegetarian means eating at the end of a short food hain; however, not all land is suitale for growing rops; only suitale for animals to graze / only produes grass whih we annot eat; many susistene farmers in developing ountries need animals to provide transport / leather / other produts, as well as to provide food; animals an e used for food in winter when plant rops may e in short supply Page 76 The ost of good food 3 a (Any 2:) There are greater energy losses; eause the hikens use energy moving around; so less eggs produed per, hiken / square metre / quantity of food provided (Any 2:) They may think they taste etter; they may think they are etter for health; they may dislike the idea of hens eing reared in attery ages 4 a Transport vehiles emit pollutants (1); espeially aron dioxide, whih may ause gloal warming (1) (Any 2:) Glasshouses will need heating and lighting in winter; whih may use eletriity; generated from fossil fuels; whih produes aron dioxide; no need for this in Spain where it is warmer and light levels are higher / winter days are longer Page 77 Death and deay 1 a 100 (1) Area A 43%; Area B 34% (1) Detritivores / miroorganisms / ateria fungi; feeding on paper; whih ontained ellulose (1) d (Any 2:) More deay organisms in the wood than on the flower ed; eause of dead leaves / leaf litter; more moisture on the woodland floor than on the flower ed; eause evaporation from soil redued y dead leaves; warmer in the wood e i The type of site (wood, flower ed) (1) ii The numer of squares that had deayed (1) f Use several piees of paper in eah area, ount eah one and alulate the average (1) Page 77 Cyles 2 a Organisms suh as earthworms, whih eat dead leaves and other plant remains, are alled detritus feeders. They help to reyle the materials in the plant remains, so that they eome availale to other memers of the ommunity of organisms in the eosystem. For example, they release some of the aron in the leaves ak into the air, in the form of aron dioxide, y the proess of respiration. (3) All of them (1) (Any 2:) They eat food that has een produed y other organisms; they need organi nutrients / they need arohydrates, fats and proteins; they do not photosynthesise 4

5 B2 A DISCOVER MARTIAN LIVING! B2a answers Page 78 The aron yle 1 1 a Light intensity (1) (Any 2:) To remove aron dioxide from the air (that humans would reathe out); to add oxygen to the air (that humans need to reathe in); to provide food Page 78 The aron yle 2 2 a (Any 2:) Miroorganisms; reak down aron ompounds in dead odies / wastes; use them in respiration (whih produes aron dioxide) 70 illion tons (1) d e (Any 3:) Plants take in more aron than they give out; so they help to remove aron dioxide from the atmosphere; reduing the onentration of aron dioxide; whih traps heat and is ontriuting to a gloal rise in temperature (Any 2:) Caron ame from, animals / plants / waste materials; deomposer reak them down; parts of the deomposers / dead odies / faees remain in the soil Tiny plants / phytoplankton, remove aron dioxide for photosynthesis (1); they and sea animals release aron dioxide y respiration (1) 5

6 B2 B DISCOVER DNA! B2 answers Page 80 Enzymes iologial atalysts 1 1 Enzymes are iologial atalysts. They are protein moleules. Eah kind of enzyme only works on a partiular kind of sustrate, whih fits perfetly into a fold in the enzyme alled the ative site. (4) 2 a (Any 3:) Partiles moving faster / have more kineti energy (as temperature inreases); more frequent ollisions; more energeti ollisions; etween enzyme and sustrate (Any 3:) Enzymes are not alive so annot e killed; the enzyme is denatured (at high temperatures); the enzyme moleule loses its shape; so its sustrate annot fit into its ative site Page 80 Enzymes and digestion 3 a Mouth (1); panreas (1) It digests starh to maltose (1) Rememer: Chek whih grade you are working at. d Bile neutralises the aid from the stomah; it is produed in the liver / stored in the gall ladder / flows in down the ile dut; when there is food in the stomah / food moving out of the stomah; ontains a ase / ontains sodium hydrogenaronate (3) Page 81 Enzymes at home 1 a (Any 2:) Haemogloin (from lood) is a protein; proteases reak down proteins; turns them into amino aids; that an e washed away This is the optimum temperature for the enzymes in them (1); enzymes are denatured if they get too hot (1) Hands / ells, ontain proteins (1); the enzymes ould start to digest these proteins (1) Page 81 Enzymes and industry 2 a DNA / genes, have een altered (1); addition of genes from a different (speies of) organism (1) amylase maltase isomerase starh maltose gluose frutose Less needs to e used so heaper for manufaturers (1); and fewer alories / kilojoules for dieters (1) d Reations work too slowly at lower temperatures / optimum temperature for enzymes is 40 ºC or aove (1) (2) e (Any 2:) Anti-GM feelings among some people muh of this is not founded on any sientifi understanding; it is very unlikely; there would e health risks from the GM potatoes / disussion of health risks given in answer unlikely; that the GM potatoes would ause any environmental damage / disussion of environmental damage given in answer 6

7 B2 B DISCOVER DNA! B2 answers Page 82 Respiration and energy 1 a Caron dioxide (1) Every ell in the ody (1) (Any 2:) Aeroi respiration takes plae in mitohondria so many mitohondria; supply a lot of energy; sperm need a lot of energy for swimming Page 82 Removing waste: lungs 2 a Oxygen in exhaled air around 16% (1); nitrogen in inhaled air around 79% (1) Body ells use oxygen in respiration (1); so lood arriving at the lungs is low in oxygen (1) d Oxygen moves etween the alveoli and the lood (1); y diffusion (1); down a onentration gradient (1); diffusion only ours until onentrations are equal (another reason is that not all of the air that is reathed into and out of the lungs ever reahes the alveoli) (1) Might have a greater onentration of aron dioxide (1); eause ells are produing aron dioxide more rapidly so onentration of aron dioxide in the lood arriving at the lungs is greater (1) Page 83 Removing waste: liver and kidneys 1 a There is more urea in the urine than in the lood eause the kidneys remove urea from the lood (1) Gluose is useful to the ody (1); it provides energy (1) If there are too few sodium or hloride ions, the kidneys an keep most of them in the lood (1); if there are too many, they an exrete more of them in the urine (1) Page 83 Homeostasis 2 a (Any 2:) In sweat, in reath, in faees (Any 2:) More sweat is lost on hot days; so there is less water in the ody; so the kidneys onserve water Temperature (1); gluose onentration (1) 3 (Any 2:) Their ells ontain a more onentrated solution than water; so water enters their odies y osmosis; through the gills; they need to exrete dilute urine to redue the amount of water in the ody 7

8 B2 B DISCOVER DNA! B2 answers Page 84 Keeping warm, staying ool 1 a Enzymes; are denatured y high temperatures; so annot atalyse metaoli reations (2) The rain measures the temperature of the lood flowing through (1); it temperature sensors in the skin measure the temperature of the environment (1) i Water in sweat evaporates (1); taking heat from the skin (1) ii Dilate / get wider (1) iii More lood flows near to the surfae of the skin (1); loses heat y radiation (1) Page 84 Treating diaetes 2 a It would rise (1); and stay high for some time (1) (Any 1:) No insulin will e produed to lower the lood gluose level; it will only fall as the ody ells use it up (in respiration) Take are aout when he eats foods ontaining arohydrates and how muh arohydrate he eats (1) 3 a (Any 2:) The dog had no panreas; so did not make insulin; it was given an injetion of gluose (Any 2:) The lood gluose onentration was very high; eause the dog had no panreas / there was no insulin; that would normally lower the lood gluose onentration (in normal irumstanes there is no gluose in the urine) (Any 2:) Yes; the hypothesis is supported; in a dog with no panreas the lood gluose onentration eame too high; injeting panreas extrat lowered the lood gluose level Page 85 Cell division mitosis 1 a (2) Genetially (1) 2 a 2 (one in eah set of hromosomes) (1) Mitosis (1) (Any 2:) The ell ould divide unontrollale; forming a tumour; aner ould develop Page 85 Gametes and fertilisation 3 a So that after fertilisation the new ell has the orret numer of 46 (1) i Meiosis (1) ii (Any 3:) Copies of the hromosomes are made; hromosomes from eah set pair up; then separate as the ell divides; it divides twie; forming four ells eah with one set of hromosomes 4 a A variety of a gene (1) (Any 3:) Some harateristis are determined y genes; the parents may have different mixtures of alleles; so the gametes also have different mixtures of alleles; so the offspring have different mixtures of alleles (and therefore harateristis) 8

9 B2 B DISCOVER DNA! B2 answers Page 86 Stem ells 1 a i A ell that is not yet speialised / a ell that an divide to form other speialised ells (1) ii The development of an unspeialised ell into one that is speialised for a partiular funtion (1) i Emryo stem ells an form every different kind of ell (1); one marrow stem ells an only form lood ells (1) ii Emryo stem ells ould e made to produe new nerve ells (1); whih ould help to mend the spinal ord (1) 2 (Any 2:) Take stem ells from an emryo; plae them in the rain where the ells have died; the stem ells may e ale to form speialised nerve ells; that serete dopamine Page 86 Chromosomes, genes and DNA 3 a DNA (1) The sequene of ases in the DNA determines the sequene of amino aids in the proteins that are made (1) i Can diagnose inherited illness efore a person has symptoms / hek for faulty genes in an emryo during IVF so that one with orret genes an e implanted (1) ii If a person is going to develop a geneti illness, they might prefer not to know / insurane ompanies might want to test a person to find out if they have genes that might make them ill or shorten their life (1) Page 87 Inheritane 1 a T (1); its harateristi appears even when the other allele is present (1) t and t (1) 2 a BB (1) (1) (in eah sperm) (1) d (3) Page 87 How is sex inherited? 3 The father s sperm (1); whih ould arry either an X hromosome (1); or a Y hromosome an egg always arries an X hromosome (1) 4 Female (1); they have two X hromosomes (1) 9

10 B2 B DISCOVER DNA! B2 answers Page 88 Inherited disorders 1 The allele for Huntington s disease must e dominant (1); for the hild to get this allele at least one of her parent s must have it (1); and will therefore have the disorder (1) 2 a There is therefore a 1 in 4 hane that a hild will have the alleles ff and therefore have ysti firosis (4) She ould have a hild with ysti firosis (1); if she is a arrier (Ff) and her partner is also a arrier (1); ut she may not e a arrier, in whih ase she annot have a hild with the disorder (1) Page 88 DNA fingerpriting 3 (Any 4:) Possile father B is the atual father; the hild has some ands that have not ome from its mother; these ands must have ome from its father; not all of these ands are present in possile father A; they are all present in possile father B 10

iii Neurones carry information in the form of electrical impulses. Sensory neurones carry impulses from receptors to the central nervous system.

iii Neurones carry information in the form of electrical impulses. Sensory neurones carry impulses from receptors to the central nervous system. Page 4 Coordination 1 a Brain (1); spinal ord (1) i Motor (1) i Neurones arry information in the form of eletrial impulses. Sensory neurones arry impulses from reeptors to the entral nervous system. (3)