CellsIB MYP Sciences: Topic test

1. 1
   A student in Vancouver places a drop of pond water on a slide and looks at it with a light microscope. The eyepiece lens is ×10 and the objective lens in use is ×40. She draws one single-celled organism so that her drawing has the same magnification as the microscope image. The drawing is 12 mm long.

   (a)

   What is the total magnification when these two lenses are used together?

   [1 mark]

   • A×50
   • B×30
   • C×400
   • D×4000

   (b)

   The student wants to give the length of the organism in micrometres. How many micrometres are there in 1 millimetre?

   [1 mark]

   • A1000
   • B100
   • C10
   • D1 000 000

   (c)

   Calculate the actual length of the organism in micrometres. Show your working.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A scientist in Jakarta compares a cell from the leaf of a mangrove tree with a muscle cell from a mangrove crab.

   (a)

   Which structure absorbs light energy in the mangrove leaf cell?

   [1 mark]

   • ANucleus
   • BChloroplast
   • CCell wall
   • DPermanent vacuole

   (b)

   Which structure releases energy from glucose in both cells?

   [1 mark]

   • ACell membrane
   • BChloroplast
   • CNucleus
   • DMitochondrion

   (c)

   State two structures that are found in the mangrove leaf cell but not in the crab muscle cell.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A physiologist in La Paz, Bolivia, studies the blood of people who live 3600 m above sea level, where the air contains less oxygen. Compared with people who live at sea level, the residents of La Paz have more red blood cells in each cubic millimetre of blood.

   (a)

   Describe three features of a red blood cell that help it to carry oxygen.

   [3 marks]

   (b)

   Explain how having more red blood cells helps the people of La Paz to stay active at this altitude.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A hospital in Warsaw treats people with serious burns by growing new skin from stem cells. A small sample of the patient's own skin is taken, and the stem cells in it are grown in a laboratory, where they divide by mitosis and become specialised skin cells. The new skin is then grafted onto the burn. The treatment is expensive, but no donor is needed and the patient's body does not reject the new skin. A doctor also warns that cells that divide too often, out of control, can form tumours.

   (a)

   Explain how mitosis produces new skin that is genetically identical to the patient's own skin, and describe what is different about the cell division that forms a tumour.

   [6 marks]

   (b)

   Evaluate the use of stem cell treatments such as this one. Consider benefits and drawbacks, and reach a justified conclusion.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A gardener in Marrakech grows mint. She makes new plants in two ways: by planting stem cuttings taken from one parent plant, and by collecting seeds from flowers that were pollinated by another mint plant.

   (a)

   Which statement describes the new mint plants grown from the stem cuttings?

   [1 mark]

   • AThey show a lot of variation from each other
   • BThey have genes from two parents
   • CThey are made when two gametes join
   • DThey are genetically identical to the parent plant

   (b)

   Which is an advantage of growing mint from seeds rather than from cuttings?

   [1 mark]

   • AAll the plants will keep the best features of the parent
   • BThe offspring show variation, so some may survive a new disease
   • COnly one parent plant is needed
   • DNo flowers or gametes are involved

   (c)

   Describe one advantage and one disadvantage of growing mint from cuttings.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A school nurse in Melbourne is explaining human reproduction to a class of 15-year-olds. She describes how sperm cells are made in the male reproductive system, where fertilisation can happen in the female reproductive system, and how a fertilised egg develops into a baby.

   (a)

   Which organ of the male reproductive system makes sperm cells?

   [1 mark]

   • ATestis
   • BPenis
   • CSperm duct
   • DUrethra

   (b)

   Into which structure does the developing embryo sink during implantation?

   [1 mark]

   • AOviduct
   • BOvary
   • CLining of the uterus
   • DVagina

   (c)

   Outline the role of the placenta during pregnancy.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   On a farm in Argentina, the gene for horns in cattle has two alleles. The allele for being polled (having no horns), P, is dominant over the allele for horns, p.

   (a)

   A polled bull could have the genotype PP or Pp. Explain what is meant by the terms genotype and phenotype, and why these two bulls look the same.

   [3 marks]

   (b)

   Two heterozygous polled cattle are crossed. Use a Punnett square to show the cross, and give the expected ratio of polled to horned calves and the probability that a calf will have horns.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A tree nursery in Quebec grows maple trees. Each maple fruit has a flat 'wing' that makes it spin as it falls from the tree. The nursery produces new trees in two ways: by planting seeds, and by taking cuttings from its best trees.

   (a)

   A student suggests that the longer the wing of a maple fruit, the longer it stays in the air, so the further the wind can carry it. Design an investigation to test this idea. Include a hypothesis with a reason, the variables, the method and a safety precaution.

   [6 marks]

   (b)

   Evaluate the two methods the nursery uses to produce new trees, and justify which it should rely on.

   [6 marks]

   Total for question 8: 12 marks

End of questions