Biology: Cells, Microscopy and Genetics - Worksheets, Questions and Revision

20 original exam-style questions - 11 pages of questions with a full mark scheme - free printable PDF.

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13+ · Biology

CE.S-B4 Biology: Cells, Microscopy and Genetics

ISEB COMMON ENTRANCE ISEB Common Entrance Biology (13+) · Calculator allowed · about 80 minutes
Total Marks
Name: _______________________________    Date: ____ / ____ / ______
Answer ALL questions. Show all your working.
1
The diagram shows a light microscope, with parts labelled A to F.
Figure (to be drawn): Diagram of a light microscope, labelled A to F. A points to the lens at the very top, which you look through. B points to a large knob on the side of the microscope, used for rough/large focusing adjustments. C points to a smaller knob next to it, used for fine focusing adjustments. D points to one of several lenses mounted on a rotating turret just above the stage. E points to the flat platform, with clips, where the microscope slide sits. F points to the lamp at the base of the microscope, shining upward through the specimen.
(a)Identify parts A to F on the diagram.(6)
(b)State the function of the objective lens, and the function of the focusing knobs.(2)
(Total for Question 1 is 8 marks)
2
A student wants to prepare a temporary mount of onion cells to view under a light microscope. The steps below are in the wrong order.

W: Place a drop of water in the centre of a clean microscope slide.
X: Using forceps, peel a thin, transparent layer from the inside of an onion and place it flat in the drop of water.
Y: Add a drop of iodine solution next to the specimen.
Z: Lower a coverslip onto the specimen at an angle, using a mandrel (needle) to guide it down slowly.
(a)Write the letters W, X, Y and Z in the correct order.(1)
(b)Explain why the iodine solution is added to the specimen.(1)
(c)Explain why the coverslip should be lowered at an angle using a mandrel, rather than dropped straight down onto the specimen.(1)
(d)Explain why the student should first view the specimen under low power, before switching to high power.(1)
(Total for Question 2 is 4 marks)
3
Microscopes are used to view specimens that are too small to see with the naked eye.
(a)State what is meant by the term 'magnification'.(1)
(b)State one advantage of using an electron microscope rather than a light microscope, and explain why this is an advantage.(2)
(c)State one limitation of using an electron microscope compared with a light microscope.(1)
(Total for Question 3 is 4 marks)
4
A student examines an onion epidermis cell under a light microscope and draws it. In her drawing, the length of the cell measures 45 mm. The actual length of the real cell is 0.09 mm.
(a)Calculate the magnification of the student's drawing. Use the formula: magnification = size of image / size of real object.(2)
(b)The student now wants to draw the same cell at a magnification of x800. Calculate the length, in mm, that she should draw the cell.(2)
(c)Convert the actual cell length of 0.09 mm into micrometres (1 mm = 1000 micrometres).(1)
(Total for Question 4 is 5 marks)
5
The image below is a photograph of a plant cell taken through a microscope. The photograph includes a scale bar, labelled '50 micrometres (50 um)'. When measured with a ruler on the printed photograph, the scale bar is 25 mm long.
Figure (to be drawn): A photograph of a plant cell taken through a light microscope, showing a cell wall, a large central vacuole, a nucleus and several chloroplasts. In the bottom corner of the photograph is a short black scale bar, labelled '50 micrometres (50 um)'.
(a)Calculate the magnification of the photograph.(2)
(b)A chloroplast inside the cell has a real diameter of 5 micrometres. Calculate how long this chloroplast should appear in the photograph, in mm, at this magnification.(2)
(c)State why photographs or drawings of specimens taken with a microscope should include a scale bar or a stated magnification.(1)
(Total for Question 5 is 5 marks)
6
Body cells in humans divide by a type of cell division called mitosis.
(a)State two reasons why the human body needs cells to divide by mitosis.(2)
(b)State how the number of chromosomes in each of the two new cells produced by mitosis compares with the number of chromosomes in the original (parent) cell.(1)
(c)Explain why it is important that the two new cells produced by mitosis are genetically identical to the parent cell.(1)
(d)Name one part of the human body where cells frequently divide by mitosis to replace old or damaged cells.(1)
(Total for Question 6 is 5 marks)
7
The table below compares mitosis and meiosis, two types of cell division. Some information is missing.
Figure (to be drawn): Table with columns Feature | Mitosis | Meiosis. Rows: 'Number of divisions' - Mitosis: one, Meiosis: X (blank to fill in); 'Number of new cells produced' - Mitosis: two, Meiosis: Y (blank to fill in); 'Chromosome number in each new cell, compared with the parent cell' - Mitosis: the same as the parent cell, Meiosis: Z (blank to fill in); 'Are the new cells genetically identical to each other?' - Mitosis: yes, Meiosis: no; 'Type of cell produced' - Mitosis: body (somatic) cells, Meiosis: gametes (sex cells).
(a)State the missing values X, Y and Z in the table.(3)
(b)Explain why it is important that gametes contain half the number of chromosomes of normal body cells.(2)
(c)State the parts of the human body where meiosis takes place.(1)
(Total for Question 7 is 6 marks)
8
Match each term (gene, chromosome, allele, DNA, genome) to its correct definition below.

(i) A thread-like structure, made of tightly coiled DNA, found in the nucleus of a cell.
(ii) A section of DNA that contains the instructions for a particular characteristic or protein.
(iii) A different version of the same gene.
(iv) The chemical, shaped like a double helix, that carries the genetic code in the nucleus of a cell.
(v) The complete set of genetic material (all the DNA) of an organism.
(Total for Question 8 is 5 marks)
9
In humans, the ability to roll your tongue is controlled by a single gene. The allele for tongue rolling (R) is dominant over the allele for non-rolling (r).
(a)State what is meant by the term 'dominant allele'.(1)
(b)Two parents are both heterozygous for this gene (genotype Rr). Draw a genetic diagram (Punnett square) to show all the possible genotypes of their children.(2)
(c)State the expected ratio of tongue-rollers to non-rollers among the children, and calculate the percentage chance that a child of these parents will not be able to roll their tongue.(2)
(Total for Question 9 is 5 marks)
10
In pea plants, purple flower colour (allele P) is dominant over white flower colour (allele p).
(a)A pea plant with purple flowers is crossed with a pea plant with white flowers (genotype pp). All of the offspring have purple flowers. State the genotype of the purple-flowered parent plant, and explain how the results of this cross support your answer.(2)
(b)A different purple-flowered pea plant is crossed with a white-flowered plant (pp). This time, approximately half of the offspring have purple flowers and half have white flowers. State the genotype of this second purple-flowered parent plant, and use a genetic diagram to show why this cross produces approximately equal numbers of purple- and white-flowered offspring.(3)
(Total for Question 10 is 5 marks)
11
Eye colour can be modelled simply using one gene, where the allele for brown eyes (B) is dominant over the allele for blue eyes (b). A mother and father both have brown eyes, but their son has blue eyes.
(a)Explain, using genotypes, how two brown-eyed parents can have a blue-eyed child.(3)
(b)State the genotype of the son.(1)
(c)State whether the son is homozygous or heterozygous for this gene.(1)
(Total for Question 11 is 5 marks)
12
Differences between individuals of the same species are called variation.
(a)State two causes of variation between individuals of the same species.(2)
(b)A mutation is a random change to an organism's DNA. Explain how a mutation could introduce a new source of variation into a population.(2)
(Total for Question 12 is 4 marks)
13
The table below lists four adaptations found in different organisms.
Figure (to be drawn): Table with columns Adaptation | Type of adaptation (blank to fill in). Rows: 1) 'A polar bear has a thick layer of fat (blubber) and dense fur to keep warm.'; 2) 'A woodlouse moves towards dark, damp places and away from bright light.'; 3) 'Bacteria living in hot springs produce enzymes that keep working normally at very high temperatures.'; 4) 'A fennec fox (a desert fox) is most active at night and rests in an underground burrow during the hottest part of the day.'
(a)For each adaptation 1 to 4 in the table, state whether it is a structural, functional or behavioural adaptation.(4)
(b)Explain why adaptations such as these are important for a species' survival.(2)
(Total for Question 13 is 6 marks)
14
A population of beetles living on tree bark is originally mostly grey in colour, though a few beetles are naturally born darker due to variation in their genes. Nearby factories then begin producing smoke and soot, which gradually blackens the tree bark over many years. Explain how the colour of the beetle population is likely to change over many generations, using ideas about variation, natural selection and inheritance.
(Total for Question 14 is 6 marks)
15
A class investigates camouflage. They scatter 100 small paper 'moths' onto a patch of green grass: 50 are green and 50 are brown. One student acts as a 'predator' and has 30 seconds to collect as many moths as possible. The results are shown in the table.

Moth colour: Green, Brown
Number collected: 12, 34
(a)Calculate the percentage of each colour of moth that was collected by the predator.(3)
(b)Use these results to explain which colour of moth was better camouflaged against the green grass.(2)
(c)Suggest one way this investigation could be made a fairer test.(1)
(Total for Question 15 is 6 marks)
16
Some bacteria, called extremophiles, live in extremely hot environments, such as deep-sea hydrothermal vents, where temperatures can exceed 100 degrees C.
(a)Suggest one functional adaptation that allows these bacteria to survive such high temperatures.(1)
(b)Explain why an enzyme from a normal (non-extremophile) bacterium would stop working at these very high temperatures.(2)
(c)Give one other example of an organism adapted to survive in an extreme environment, and briefly state its adaptation.(1)
(Total for Question 16 is 4 marks)
17
A mitochondrion has an actual length of 2 micrometres. A photograph taken using an electron microscope shows the mitochondrion magnified x25,000.
(a)Calculate the length of the mitochondrion as it appears in the photograph. Give your answer in millimetres (1 mm = 1000 micrometres).(3)
(b)A ribosome has an actual diameter of about 25 nanometres (1 micrometre = 1000 nanometres). Calculate the diameter of the ribosome in micrometres, and explain why a ribosome cannot be seen clearly using a light microscope, even at its maximum magnification.(3)
(Total for Question 17 is 6 marks)
18
Gregor Mendel studied inheritance in pea plants during the 1800s. He grew large numbers of pea plants for each cross (not just one or two), and carefully counted and recorded the offspring produced.
(a)Suggest why it was important for Mendel to use large numbers of pea plants in his experiments, rather than just a few.(2)
(b)Suggest one way that Mendel's discoveries about inheritance are still useful today.(1)
(Total for Question 18 is 3 marks)
19
Cystic fibrosis is a genetic disorder caused by a recessive allele (f). The dominant allele (F) does not cause the disorder. Both parents in a family are carriers, with genotype Ff, but neither parent has cystic fibrosis.
(a)State the genotype of each parent, and explain why neither parent has cystic fibrosis despite carrying the recessive allele.(2)
(b)Draw a genetic diagram (Punnett square) for this cross, and use it to calculate the percentage probability that a child of these parents will have cystic fibrosis.(2)
(c)Calculate the percentage probability that a child of these parents will be a carrier (Ff) but will not have cystic fibrosis.(2)
(Total for Question 19 is 6 marks)
20
A cactus is a plant that is well adapted to survive in a hot, dry desert environment. Describe three structural adaptations of a cactus, and explain how each adaptation helps it survive in the desert.
(Total for Question 20 is 6 marks)
Mark scheme · CE.S-B4 Biology: Cells, Microscopy and Genetics

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19

Question 20