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AQA BIOL2 Biology Unit 2 Exam - 26th May 2011 watch

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    (Original post by liviaaa)
    I think it was just more red blood cells, means more haemoglobin, so can carry a larger amount of oxygen to respiring cells?

    Hmm.. because there are many people in small area (easier transmission), sick and elderly people, have weaker immune systems so more likely to be effected. Not sure what else - can you think of anything?
    Erm aside from what you have I don't think there is much more, I guess you could say that there is increased doctor-patient contact and therefore increased transmission if there is a lack of hygiene i.e doctor not washing hands after patient contact or something along those lines.. I guess they would only ask for max 2 reasons so we're okay
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    (Original post by liviaaa)
    I think it was just more red blood cells, means more haemoglobin, so can carry a larger amount of oxygen to respiring cells?

    Hmm.. because there are many people in small area (easier transmission), sick and elderly people, have weaker immune systems so more likely to be effected. Not sure what else - can you think of anything?
    Doctors moving from patient to patient as vehicles for the disease?
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    (Original post by Rizzy J)
    Possibly tissue fluid formation or movement of water thriugh roots ( apoplast/symplastic pathway) transpiration, antibiotic resistance
    With antibiotic resistance that's basically just natural selection right?
    There's variation in the population. Mutation occurs which results in an allele with resistance to a certain antibiotic. The bacteria with the advantageous allele will survive antibiotic treatment and those without will die. The ones who survive can grow and reproduce, pass on the advantageous allele and its frequency will increase. The antibiotic will become less effective. The gene to resistance can be passed on by either horizontal gene transmission between bacteria of different species or by passing it along to offspring by vertical gene transmission.

    Does that sound about right to you?
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    (Original post by ScienceGeek3)
    Erm aside from what you have I don't think there is much more, I guess you could say that there is increased doctor-patient contact and therefore increased transmission if there is a lack of hygiene i.e doctor not washing hands after patient contact or something along those lines.. I guess they would only ask for max 2 reasons so we're okay

    (Original post by SmithytheDrummer)
    Doctors moving from patient to patient as vehicles for the disease?
    Thanks
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    (Original post by parallal)
    Once again, just checking my knowledge. Hope I'm not being annoying.

    Comparisons between blood vessels:

    Arteries: More elastic (to expand and recoil to even out blood pressure) and muscle fibres (to contract and relax to help push blood along) than veins, smaller lumen, no valves, carries oxygenated blood (except pulmonary artery which carries deoxygenated blood). Also has more muscle fibres/less elastic fibres than arterioles.

    Veins: Less elastic and muscle fibres than arteries, larger lumen, valves (to prevent back-flow of blood), carries deoxygenated blood (except pulmonary vein which carries oxygenated blood)

    Capillaries: One cell thick (for short diffusion pathway), flat cells (to reduce friction), smallest of the blood vessels, closer to tissues/cells so exchange occurs in capillaries, many branching capillaries increase surface area, small lumen

    Arterioles: More elastic fibres than arteries (for vasoconstricion/vasodilation), less muscle fibres than arteries

    Venules: I actually don't know that much about these. Don't really remember any past questions on venules.

    All blood vessels: Have an layer, one cell thick, called the endothelium to prevent the blood from sticking to the sides of the vessel and reduces friction. surrounded by a layer of protein called collagen to protect the vessel from pressure
    Might be worth noting that arteries have thicker walls to prevent them from bursting. And, about venules, they don't really come up. It's not in the NT textbook anyway.
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    If anyone has done June 2010 could you explain how to do 5dii to me please?!
    I really don't understand how you get 8 for the answer:confused:

    (It was the question about how many different types of gamete could be produced from the cell as a result of different combinations of maternal and paternal chromosomes...)
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    (Original post by liviaaa)
    Hmm this question was in a paper:

    The elephant is a very large animal. It has adaptations to increase heat loss from its
    body surface. A mouse is a very small animal and it has adaptations to reduce heat
    loss from its body surface. Explain why these animals have different adaptations for
    heat loss.

    The markscheme said:

    -Elephant has smaller surface area to volume ratio
    -Elephant generates more heat - wouldn't it be less heat, as they loose heat more slowly?
    I'm sure for that question you should of refer to the mouse as it's easier to explain:

    -Mouse has a large surface area to volume ratio
    -More heat is lost per unit mass
    -Smaller mammal has greater rate of respiration
    -Oxygen required for respiration
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    Out of interest, what UMS did everyone get in Unit 1? Quote me
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    (Original post by qwerty54321)
    Out of interest, what UMS did everyone get in Unit 1? Quote me
    I got a C in jan, hoping for an 80 this time (paper went well )
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    (Original post by oHellno)
    Might be worth noting that arteries have thicker walls to prevent them from bursting. And, about venules, they don't really come up. It's not in the NT textbook anyway.
    Ok, thanks.
    There isn't much information on them in the Hodder Education textbook either.
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    Does anyone think we'll get a magnification question?
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    Re: AQA BIOL2 Biology Unit 2 Exam - 26th May 2011
    Out of interest, what UMS did everyone get in Unit 1? Quote me
    I got 88
    And I spent all that time worrying about how Ididn't write anything about competitve inhibitors on the inhibitor question:eek:
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    (Original post by parallal)
    Does anyone think we'll get a magnification question?
    doubt it, thats in unit 1 isn't it, never seen it in a unit 2 paper?
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    (Original post by LifeIsGood)
    I'm sure for that question you should of refer to the mouse as it's easier to explain:

    -Mouse has a large surface area to volume ratio
    -More heat is lost per unit mass
    -Smaller mammal has greater rate of respiration
    -Oxygen required for respiration
    The markscheme said only the 2 points mentioned above in my other post?
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    Anyone who has the June 2010 paper to hand, be kind enough to explain the questions 5c (why not independent segregation), and 5d to me, (on meiosis) much appreciated !
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    UNIT 2 FUNDAMENTAL REVISION questions


    Cells and Cell differentiation
    1. State all the differences between plant and animal cells.
    2. Draw a palisade cell and label it.
    3. Draw and label a chloroplast, stating its function.
    4. State the main function of the following organelles: cell-surface membrane, nucleus, mitochondrion, lysosome, ribosome, rough and smooth endoplasmic reticulum and Golgi apparatus.
    5. What does differentiation mean?
    6. Define tissue and organ.

    Carbohydrates
    7. Draw the structure of ? glucose and show how it links to form cellulose.
    8. Give the structure and functions of starch, glycogen and cellulose related to animals and plants.

    Size and surface area
    9. Explain the relationship between size and surface area to volume ratio.
    10. List some things which are exchanged through the surface area of an organism.

    Gas Exchange
    11. Name and describe the gas exchange surface in insects.
    12. Name and explain the gas exchange surface in fish.
    13. Describe how the countercurrent principle works.
    14. Describe how gas exchange occurs in plants.
    15. Define diffusion.
    16. List and explain the features of xerophytic plants which help to reduce water loss.

    Mass Transport
    17. Name the blood vessels which enter and leave the following organs: heart, liver and kidney.
    18. Name the blood vessels that supply the heart with blood.
    19. Describe the structure of the following and relate the structure to the function of the blood vessel: arteries, arterioles, veins and capillaries.
    20. How is tissue fluid formed?
    21. What is lymph?
    22. Name and describe the two ways in which water moves through the cells of a root.
    23. Name and explain the two methods by which water moves though the xylem.
    24. List the factors which affect the rate of transpiration in a plant.


    Haemoglobin and oxygen dissociation curves
    25. Describe the structure of haemoglobin.
    26. Name three factors which will move a dissociation curve to the right.
    27. What is the advantage of a curve to the right?
    28. Under what circumstances would a curve move to the left? What is the advantage of this?

    DNA
    29. Name the three components of a nucleotide.
    30. Name the four bases in DNA and give the complementary base pairings.
    31. Name the bonds which hold the bases together and give the number of bonds that are formed in each base pair.
    32. Define a gene; what is an alternative form of a gene called?
    33. What does the triplet code of DNA mean?
    34. Does all DNA code for polypeptides? Explain.
    35. State the differences in DNA between prokaryotic and eukaryotic organisms.

    Mitosis
    36. Explain how DNA replicates.
    37. In which stage of the cell cycle does DNA replication occur?
    38. Name the stages of mitosis and explain the main events which occur at each stage.
    39. Why is mitosis necessary?
    40. Explain the link between mitosis and cancer.
    41. Why does chemotherapy cause hair loss?

    Meiosis
    42. Define haploid and diploid.
    43. What are the main differences between mitosis and meiosis?
    44. What is a bivalent?
    45. State and explain the two processes which occur during meiosis that account for the genetic variation in gametes.

    Genetic diversity
    46. What is genetic diversity?
    47. List and explain three ways in which genetic diversity can be reduced in a population.

    Variation
    48. What causes similarities and differences between individuals within a species?
    49. What is it called when there are differences within a species, and when there are differences between species?
    50. Name the two types of variation and give details on how they can be graphically represented, how they are genetically controlled and whether they are affected by any other factors.
    51. Explain how to calculate mean, mode and median from a set of data.
    52. What is standard deviation?

    Genetic variation in bacteria
    53. What is an antibiotic?
    54. What is osmotic lysis?
    55. What is a gene mutation?
    56. How may bacteria acquire resistance to antibiotics?
    57. What is the difference between horizontal and vertical transmission?
    58. Why is tuberculosis difficult to treat?
    59. Why is MRSA difficult to treat?

    Taxonomy
    60. What is taxonomy?
    61. What is meant by a hierarchy?
    62. What is meant by phylogenetic grouping?
    63. Define a species.
    64. List the main hierarchy groups in descending order.

    Genetic comparisons
    65. Explain how DNA base sequences are used to work out relationships between organisms.
    66. Explain how DNA hybridisation works.
    67. Explain the basis of how amino acid sequences can be used to work out relationships between organisms.
    68. What do immunological comparisons tell us about how closely related species are to each other?
    69. Why is courtship behaviour important?

    Biodiversity
    70. Define diversity
    71. What is an index of diversity?
    72. Describe how deforestation may reduce species diversity.
    73. Describe how modern farming techniques may also reduce species diversity.
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    (Original post by liviaaa)
    The markscheme said only the 2 points mentioned above in my other post?
    Hmm that's interesting. Can you give me the paper you got it from please? [just the year] cuz the same thing came up in June 2010
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    UNIT 2 FUNDAMENTAL REVISION – ANSWERS

    UNIT 2 FUNDAMENTAL REVISION – ANSWERS



    Cells and cell differentiation
    1. Plant cells have a cellulose cell wall, a large vacuole, starch granules and some have chloroplasts.

    4. Cell surface membrane: controls the movement of substances in and out of a cell; nucleus: controls the activities of a cell; mitochondrion: the site of some stages of respiration; lysosome: contain enzymes which can digest organelles or cells; ribosome: site of protein synthesis; rough endoplasmic reticulum: transport and modification of proteins; smooth endoplasmic reticulum: synthesise, store and transport lipids; Golgi apparatus: packaging and transport of glycoproteins and enzymes and forms lysosomes.
    5. Differentiation is where newly formed cells change their structure to become specialised for specific functions.
    6. Tissues are a group of similar cells which perform the same function; an organ is an aggregation of different tissues grouped together to form an organ which performs a specific function that combines the roles of its tissues.


    Carbohydrates
    7.










    8. Starch is made of chains of ? glucose linked together by glycosidic bonds which form a tight coil. It is a very compact molecule so a lot can be stored in a small space, it is insoluble so it does not draw water into cells, and it is easily hydrolysed to release the glucose ready for respiration. Starch is stored in animal cells. Glycogen is very similar to starch but is composed of shorter chains and it is highly branched. It is stored as small granules in animal cells. Cellulose is made of ? glucose and forms long straight chains which run parallel to each other and held together by hydrogen bonds which give cellulose its strength as a structural molecule in plant cell walls.

    Size and surface area
    9. As an organism gets bigger, its surface area to volume ratio gets smaller.
    10. Oxygen, carbon dioxide, heat, glucose.

    Gas exchange
    11. Spiracles on the surface lead to tracheae which divide into smaller tracheoles (which are the exchange surface) and these extend into the muscle fibres.
    12. Gills are made of gill filaments which support the gill lamellae through which gas exchange occurs.
    13. Blood and water flow in opposite directions so there is always a concentration gradient along the whole length of the gill filament.
    14. The gas exchange surface is the cell surface membranes of the spongy mesophyll cells. The gases enter and leave through stomata on the underside of leaves and move down a concentration gradients.
    15. Diffusion is the net movement of molecules from an area where they are highly concentrated to an area where their concentration is lower, i.e. down a concentration gradient.
    16. Thick waxy cuticles reduce water loss by evaporation; rolled up leaves protect the stomata and reduces the water potential gradient; hairy leaves trap moisture next to the leaves and so reduces water potential gradients; sunken stomata also trap moist air and small leaves which are circular reduces surface area to volume ratios and therefore water loss.

    Mass Transport
    17. Heart: vena cava, pulmonary artery, pulmonary vein, aorta; Liver: hepatic artery, hepatic portal vein, hepatic vein; Kidney: renal artery and renal vein.
    18. Coronary arteries.
    19. Arteries carry blood away from the heart and have a thick wall to prevent bursting under pressure. They have a thick layer of elastic tissue to allow for stretch and recoil which maintains blood pressure and evens out the flow. Arterioles have more muscle than elastic tissue which allows constriction of the vessel to control the flow of blood into capillaries. Veins have thin walls as the blood is at a lower pressure. There are valves to ensure that the blood flows in one direction only. Capillaries are where exchange of substances occurs so there is only a single layer of endothelial cells.
    20. Tissue fluid is formed from plasma and is forced out of a capillary at its arterial end by the high hydrostatic pressure.
    21. Lymph is the name given to the tissue fluid which does not return to the venule end of a capillary but is carried back to the blood by the lymphatic system.
    22. The apoplastic pathway moves water through the cell walls of the cortex whereas the symplastic pathway takes place through the cytoplasm of cells, passing through gaps in the cell walls called plasmodesmata.
    23. The cohesion tension theory: water molecules attract each other (cohesion) which form a continuous stream of water in the xylem. As the water evaporates from the mesophyll cells in the leaves, this creates the tension which pulls the mater molecules up the stem. Root pressure: as minerals ions are actively transported in to the xylem, the water potential is lowered so water follows by osmosis thus creating a higher hydrostatic pressure at the bottom of the xylem than further up. This pressure will move water up the xylem, particularly in small plants.
    24. Light, temperature, humidity and air movement.

    Haemoglobin and oxygen dissociation curves
    25. Haemoglobin is a protein which has a complex quaternary structure. It is composed of four polypeptide chains, each coiled into a helix. The chains are linked together to forma spherical molecule in which each polypeptide chain is associated with a haem group which contains a ferrous ion.
    26. High rates of respiration, high levels of carbon dioxide, lower pH of the blood.
    27. Haemoglobin has a lower affinity for oxygen so the oxygen is released at higher partial pressures to the respiring cells which require it.
    28. When organisms live in areas which have low partial pressures of oxygen, haemoglobin can load at lower partial pressures and as it has higher affinity for oxygen it can hold onto the oxygen for longer.



    DNA
    29. Pentose sugar, phosphate, base.
    30. Adenine pairs with thymine, cytosine pairs with guanine.
    31. Hydrogen bonds, two between A-T and three between C–G.
    32. A gene is a length of DNA which codes for a protein.
    33. Three bases code for one amino acid.
    34. No. There are sections of DNA within a gene, called introns, which do not code for the protein, and there are sections between genes, called the hyper variable regions which also do not code for a protein.
    35. Prokaryotic cells have circular, naked DNA which has few genes, whereas eukaryotic cells have linear DNA which is associated with proteins and has areas of non coding DNA.

    Mitosis
    36. The DNA helix unwinds, DNA helicase breaks the hydrogen bonds holding the two strands together. Free nucleotides are attracted to the exposed bases which complementary base pair forming hydrogen bonds. Phosphodiester bonds (deoxyribose-phosphate bonds) are formed between the nucleotides, using DNA polymerase. Each strand has acted as a template for the bases, and each strand contains one of the original strans – called semi conservative replication.
    37. Interphase
    38. Prophase – chromosomes condense, becoming shorter and fatter. Nuclear envelope disappears and spindle fibres form. Metaphase – the replicated chromosomes line up in the middle of the cell, each one attaches to a spindle fibre by its centromere. Anaphase – Spindle fibres contract, pulling the sister chromatids to opposite poles of the cell. Telophase – two sets of separated chromosomes collect at opposite ends of the cell. Nuclear envelopes form around each set, the chromosomes become long and thin and the cytoplasm divides to form two new cells..
    39. To produce genetically identical cells, for growth or repair of cells.
    40. Some cells loose the ability to control their division and undergo repeated, uncontrolled division. These are cancer cells.
    41. The drugs used in chemotherapy attack cells which are dividing fast. This includes epithelial hair cells, so hair loss occurs.

    Meiosis
    42. Haploid is the number of chromosomes present in a gamete where only one of a homologous pair is present; diploid is the number of chromosomes which are present in a body (somatic) cell where the chromosomes are present in their homologous pairs.
    43. Mitosis involves one division, produces two genetically identical daughter cells and maintains the chromosome number; meiosis involves two successive divisions, produces four genetically different daughter cells and halves the chromosome number.
    44. A pair of homologous chromosomes associated together.
    45. Crossing over of blocks of DNA between bivalents which results in a recombination of alleles in the gametes; independent assortment of homologous chromosomes which produces gametes which have a random distribution of maternal and paternal genes/chromosomes.


    Genetic diversity
    46. The difference in combinations of alleles which a species has makes members of that species vary from each other. The greater the number of different alleles that all members of a species possess, the greater the potential for genetic diversity of that species.
    47. Artificial selection: individuals with desired characteristics are used to produce the next generation. Offspring that do not exhibit that characteristic are prevented from breeding so that unwanted alleles are bred out of a population and the alleles for the desired characteristic increase in their frequency. The founder effect: a few individuals from a population colonise a new area, taking with them a small fraction of the alleles within their gene pool. The new population will show less genetic variety than the original population as their gene pool is smaller. Genetic bottlenecks occur when a disaster wipes out most of a species and the remaining few individuals only have a small percentage of the alleles which were present in the original population.

    Variation
    48. Similarities and differences may be the result of genetic factors, differences in environmental factors, or a combination of both.
    49. Differences within a species are called intraspecific varaition and differences between species are referred to as interspecific variation.
    50. Continuous variation is where there are a range of values; this is usually represented as a bell shape curve which shows normal distribution in a frequency distribution histogram. Features which show continuous variation can be influenced by the environment and are controlled by many genes. Discontinuous variation is where there are distinct groups with no overlap. These features are not usually affected by the environment and are usually controlled by one or two genes.
    51. The mean is calculated by adding together all the data and dividing the total by the number of data. The mode is the value which occurs most frequently. The median is the value in the middle of a set of data when organised in ascending order.
    52. Standard deviation is a measure of the spread of data around the mean. It is a measure of the variation within a sample.


    Genetic variation in bacteria
    53. Antibiotics are substances produced by living organisms that can destroy or inhibit the growth of microorganisms. It can also be used to describe synthetic drugs which destroy microorganisms.
    54. It is what occurs when an antibiotic has prevented the formation of bacterial cells walls, so that when water moves into the bacteria, by osmosis, the cell wall is weak and so the bacterial cell bursts.
    55. Changes in the base sequences of DNA which result in different characteristics. Bases may be added, deleted or substituted.
    56. Bacteria may have a chance, random mutation which confers resistance to an antibiotic. These bacteria live, multiply and pass the resistant gene on to all future generations.
    57. Vertical transmission is where bacteria of the same species pass their genetic material to all daughter cells during cell division. Horizontal transmission occurs by a process called conjugation, where a small piece of DNA is passed to bacteria of another species so that the recipient cell acquires new characteristics from the donor cell.
    58. Antibiotics have to be taken for long periods of time and some bacteria may become resistant to the antibiotic. These bacteria replicate so that the antibiotic no longer destroys them. Conjugation can pass the resistance gene between different bacteria so now there are multiple antibiotic resistant strains of the bacteria which cause TB.
    59. MRSA have now developed resistance to almost every known antibiotic. People in hospital are more vulnerable to infection and transmission of the bacteria by touching and cross contamination between patients is common.

    Taxonomy
    60. The theory, study and practice of biological classification.
    61. A classification system in which groups are contained within larger groups and there is no overlap between the groups.
    62. This is where the evolutionary relationships between organisms can be seen.
    63. Observable similarities and the ability to produce live, fertile offspring.
    64. Kingdom, phylum, class, order, family, genus, species.

    Genetic comparisons
    65. Species that are closely related show similarities in their DNA base sequences, whereas species that are distantly related show fewer similarities.
    66. It is based on the fact that two strands of DNA will complementary base pair. When strands from two species are allowed to base pair, hydrogen bonds will form between complementary base pairs. These hybrid strands are then separated and the temperature at which they separate is noted. The higher the temperature needed to break the hydrogen bonds, the more closely related the species, and the lower the temperature needed, the distantly related the species are.
    67. The sequence of amino acids in proteins is determined by DNA. The degree of similarity in the amino acid sequence of the same protein in two species reflects how closely related the species are.
    68. This is based on the fact that antibodies of one species will respond to specific antigens of another species. When blood serum of one species is mixed with the blood serum of another species, a precipitate is formed. The more precipitate that is formed, the more closely related the species are.
    69. It allows species to recognise members of their own species and ensures reproductive isolation; it allows both partners to identify a mate that is capable of breeding which will lead to a pair bond and synchronised mating. Mating must be successful to pass on DNA to the next generation.

    Biodiversity
    70. It is the variety of different species in a particular area.
    71. It describes the relationship between the number of species present in a community and the number of individuals in that community. It allows different habitats to be compared in terms of the variety of organisms present.
    72. Removal of trees would reduce the number of habitats and food sources available for the variety of organisms present, so the species diversity will decrease.
    73. The use of pesticides, herbicides, monoculture, selective breeding and the removal of hedgerows will all reduce the variety of species on farmland.
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    (Original post by Catchmeifyoucan)
    doubt it, thats in unit 1 isn't it, never seen it in a unit 2 paper?
    It is unit one but its on the unit 2 June 2010 paper. (Question 2b)
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    (Original post by lf1)
    Anyone who has the June 2010 paper to hand, be kind enough to explain the questions 5c (why not independent segregation), and 5d to me, (on meiosis) much appreciated !
    5ci, is specifically asking about the recombination of alleles, so must be crossing over to form Ef and eF, independant segregation just means when the homologous pairs line up randomly and hence why the haploid are all nonidentical, it's not altering the alleles.

    5d, shows a diploid cell, since the gamete is a haploid, it has one of each of the homologous pairs, so one candycane one, dot one and rod one.

    I don't understand how 5dii is 6 though???
 
 
 
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