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Assessment Schedule – 2010 Science 1.3: Describe aspects of biology (90188) Evidence Statement Q Achievement Achievement with Merit ONE Correct statement about why viruses can’t be cultured on agar (a) Examples: Viruses do not carry out life processes/are not living. OR Viruses require living cells to reproduce/replicate. Correct explanation why viruses can’t be cultured on agar AND why bacteria can (m) Examples: Viruses can only reproduce/replicate in living cells which are not on agar (a) Correct statement about why bacteria can (a) Examples: Agar contains food/ moisture that bacteria need to grow/reproduce etc (b) Correct statements. (a) eg Viruses or bacteria spread through contact/air (a) Viruses replicate in living cells then burst out to spread (or diagram ok) (a) Bacteria reproduce using binary fission /cell divides in two. (a) As bacteria build up over time they excrete waste which makes a person ill (a) Q1 Suff 3 x a statements from Parts (a)and (b) 3 x a =A Achievement with Excellence AND Bacteria need food/moisture, which is in agar, to reproduce/ carry out life processes etc Correct explanation comparing infection OR replication of bacteria and viruses OR why person gets ill (m) Discusses fully how bacteria and viruses enter the body AND reproduce AND cause illness (e) Eg: Both viruses and bacteria are spread Both bacteria and viruses can through air/contact and are be swallowed after contact/ swallowed. from the air (m) Bacteria reproduce rapidly by binary fission in warm, moist conditions, all Viruses inject genetic excreting toxins/waste which make material into a living cell, you sick when sufficient numbers are which makes viruses. They present. Viruses inject DNA into burst out and infect more cells living cells, when then are used to and Bacteria reproduce by make more viruses. These burst from binary fission/ cell divides in the cell, killing it and then infect more two (m) cells, causing more damage (e) Viruses burst the cells causing sickness/ immune system response, and bacteria produce toxins/cause sickness with their excretion (m) 2 x m from part (a) or/and (b) =M 1xe=E (can only be from part (b) Q2 Correct statement (a) (a) Eg: The dry sachet has no moisture (a) Explains why sachet has long life AND prepared yoghurt does not (m) Eg: The bacteria are dormant/inactive until water is added (a) The dried sachet has no moisture/water so the bacteria can’t grow/ are dormant, OR the bacteria are dormant until water is added Harmful bacteria may enter the yoghurt after it is made (a) AND The cold fridge temp stops the bacteria growing/reproducing etc (a) Prepared yoghurt spoils as bacteria are active/eat the yoghurt and excrete waste/ can contain airborne bacteria/cold temp slows the life processes (m) (b) Correct statement about a step or life process or conditions (a) Correct explanation of conditions needed OR explanation of a step OR a life process (m) Eg: Eg: Step 1 – need clean jars or water to avoid other bacterial contamination (a) Step 2-leaving no air space/screwing lid on ensures no other bacteria can enter (a) Adding water activates the dormant bacteria/ bacteria need moisture to grow/respire/reproduce (a) Step 3 – Hot water provides warmth (a) Milk curdles/clots when acid is produced by bacteria or acid is excreted to make the yoghurt thick (a) The bacteria have/need warmth, food and moisture (a) Q2 Suff 3 x a from Parts (a) and/or (b) = A Links at least 2 step explanations to conditions and life processes (e) Eg: Bacteria need food, moisture and warmth to carry out life processes. Bacteria need food, moisture Yoghurt is made when the bacteria eat and warmth (at least 2) to the milk/lactose (powder) and excrete carry out life processes. (lactic) acid to make the milk proteins Yoghurt is made when the clot/clump. Step 1 adds water to bacteria eat the milk/lactose activate the bacteria /needs to be clean (powder) and excrete (lactic) to avoid contamination by other acid to make the milk proteins bacteria which may make you sick. clot/clump. (m) The yoghurt bacteria start growing, reproducing by binary fission and Step 1- stops other bacteria eating by extracellular digestion, etc contaminating and secreting enzymes to break down food growing in the jar to spoil the and then absorbing it. The heat of the yoghurt or cause illness (m) hot water in step 2 ensures that these OR processes are carried out quickly as Step 2 - leaving no air heat speeds up reactions. space/screwing lid on ensures no other bacteria can enter to spoil the yoghurt or cause illness (m) OR Step 3 – Hot water provides the warmth to make the bacteria reproduce quickly/ carry out life processes faster to make the yoghurt (m) Explains a relevant life process – eg. bacteria eat by extracellular digestion secreting enzymes to break down food and then absorbing it (m) 3 x m from Part (a) and/or (b) =M 1 x e from Part (b) =E Q3 (a) Correct genotypes (a) Explains why the genotypes must be Dd (m) Dd or heterozygous (Allow other letters if clearly heterozygous) (b) Correct statement or punnet. (a) Eg: Description/ diagram of meiosis (a) Variation in meiosis can be caused by crossing over / shuffling/ independent assortment (a) D d D d DD Dd Dd dd (a) Defines 2 of allele (different versions of a gene), phenotype (physical/observed trait), gene (length of DNA coding for a trait) (a) Next child has ¾ chance of dimples (a) Only 1 has dimples due to chance / each baby has same chances (a) Eg: Both parents have the dominant trait so can be DD or Dd. Must be Dd so they can produce a dd child with no dimples (or parents can’t be dd or would have no dimples) Correct punnet AND explanation of outcomes of meiosis OR outcome related to chance. (m) Must use terms allele and gene correctly if used. Eg: Explains meiosis process (may be annotated diagram) (m) OR Meiosis is the production of gametes / sex cells, so produces cells with half the number of chromosomes. These mix at fertilization, the dominant D will show if present (m) OR Both parents have both alleles, D and d, how these combine is random for each child / not related to previous events. Chance of dimpled child phenotype is still ¾ as in punnet even though it hasn’t shown up as often as this so far. 75% chance will only be displayed in a large sample, not necessarily in only 4 children (m) AND Correct Punnett square. Discusses how meiosis produces can be produced AND links the outcome to the statistical probability of it happening. MUST include Punnett square. (e) Because both parents are heterozygous, they carry both dominant and recessive alleles for the gene. In meiosis, the homologous pairs line up and are pulled apart, ie the alleles are separated. Each gamete receives one allele for each gene, ie 1/2 the genetic material of the parent. This combines randomly at fertilization with another gamete to give the various outcomes dd, DD and Dd. For a child to have no dimples it must inherit the recessive allele from both parents. As shown in the punnet this should statistically happen ¼ of the time, but each time is random /unrelated to previous outcomes, so it is quite possible to not get correct ratios unless a very large number of children are born. AND Correct Punnett square. Q3 Suff Q4 (a) (b) 3 x a over Part a and b= A 2 x m over Part a and/or b = M Correct genotype and phenotype given (a) Explanation of genotype and phenotype given (m) Genotype is aa, phenotype is black. (a) Eg: Genotype is aa, phenotype is black. Cat must have both recessive alleles aa or it would be Agouti as Agouti is dominant and only needs one A allele to show (m) Correct statement (a) Explains process of test/back cross (m) Eg: He needs to do a test/back cross to find AA cats to breed together/AA are pure breeding for agouti (a) Breed agouti with black to find out which are AA AND punnet/s (a) Eg: He needs to do a test/back cross to find AA cats to breed together/AA are pure breeding for agouti. This means breeding the agouti with the black, if any black kittens result, the agouti parent must be Aa and not pure breeding (m) OR appropriately annotated punnets ie Punnet 1 – all agouti A A a Aa Aa a Aa Aa Punnet 2 – ½ agouti. ½ black A a a Aa aa a Aa aa (m) 1xe=E Discusses process of test cross to establish pure breeding group (e) Eg: The breeder first needs to find the AA agouti cats to breed from. By breeding the agouti cats he has with the black ones, he can see this as AA x aa will only produce Aa agouti kittens as in punnet 1. Quite a large number are needed to ensure no black kittens will result. If a single black kitten is born, the agouti parent must be Aa as in punnet 2, it must have given an a allele. When the breeder is certain he has AA individuals he can breed only these, as all offspring will be AA true breeding agouti, as no recessive alleles are present. Punnet 1 – all agouti A A a Aa Aa a Aa Aa Punnet 2 – ½ agouti. ½ black A a a Aa aa a Aa aa Q4 Suff 2xa =A 1 x a + 1 x m from (a) or (b) = M 1xe =E OVERALL SUFFICIENCY: Achieved: 3 questions out of 4 answered at achieved level or above. Merit: 1 question at achieved or above and at least 2 questions at merit. Excellence: 1 question at achieved or above, two questions at excellence.