VariationIB MYP Biology: Subtopic test

1. 1
   A class in Auckland records several features of every student: height, blood group, eye colour, mass and whether the student can roll their tongue. The teacher uses the results to introduce the idea of variation within a species.

   (a)

   Which of these features shows discontinuous variation in humans?

   [1 mark]

   • AHeight
   • BBlood group
   • CMass
   • DFoot length

   (b)

   Which of these features shows continuous variation in humans?

   [1 mark]

   • AHeight
   • BBlood group
   • CTongue rolling
   • DAttached or free ear lobes

   (c)

   Describe the difference between continuous and discontinuous variation.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Researchers in Stockholm study identical twins who were separated at birth and raised in different countries. Identical twins have exactly the same genes because they come from the same fertilised egg.

   (a)

   Which feature of the twins is most likely to differ because of their different environments?

   [1 mark]

   • AEye colour
   • BBlood group
   • CBody mass
   • DNatural hair colour

   (b)

   Which statement about identical twins is correct?

   [1 mark]

   • AThey develop from two eggs and two sperm
   • BThey have different genes because of meiosis
   • CThey never show any variation
   • DDifferences between them are caused mainly by the environment

   (c)

   Explain why identical twins raised in different countries can have different heights as adults.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A breeder in Vienna notices that the puppies in one litter, born to the same two parents, differ from each other and from their parents in coat colour and size. The smallest puppy had less access to food than its brothers and sisters.

   (a)

   Outline three sources of genetic variation in the puppies.

   [3 marks]

   (b)

   Explain why the puppies differ in size, referring to both genetic and environmental causes.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A research institute in the Philippines keeps a seed bank storing seeds of more than 100 000 rice varieties, many of which are rarely grown. In a trial, a scientist grew 50 plants of a modern high-yield variety, which are all genetically identical, and 50 plants of a traditional variety, which are genetically varied, in the same field. In a normal year the mean yield was 4.0 tonnes per hectare for the high-yield variety and 2.8 tonnes per hectare for the traditional variety. In a drought year the mean yield fell to 1.2 tonnes per hectare for the high-yield variety and 2.2 tonnes per hectare for the traditional variety. In the drought year the plant heights ranged from 88 cm to 92 cm for the high-yield variety and from 70 cm to 110 cm for the traditional variety. Some officials say the seed bank is too expensive to keep.

   (a)

   Process the data and evaluate the hypothesis that genetic variation helps a population to cope with environmental change.

   [6 marks]

   (b)

   Discuss whether the government should continue to spend money on the seed bank.

   [6 marks]

   Total for question 4: 12 marks

End of questions