Populations, adaptation and variationIB MYP Sciences: Subtopic test

1. 1
   The fennec fox lives in the Sahara Desert. It has very large ears, pale sandy fur and hairy soles on its paws. It hunts at night and shelters in a burrow during the day. Water is scarce and daytime temperatures are very high.

   (a)

   Which feature increases the surface area from which the fennec fox loses body heat?

   [1 mark]

   • AHairy soles on its paws
   • BVery large ears
   • CPale sandy fur
   • DSheltering in a burrow

   (b)

   Which statement defines an adaptation?

   [1 mark]

   • AA feature that helps an organism to survive and reproduce in its habitat
   • BA feature that an organism gains by practice during its life
   • CAny difference between two organisms of the same species
   • DThe number of organisms living in a habitat

   (c)

   Suggest how the fox's habit of hunting at night and sheltering in a burrow by day helps it to survive in the desert.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   On a small Galápagos island, ground finches feed on seeds. Scientists measured the beak depth of many birds and found values between 7 mm and 12 mm, with most birds near 9 mm. During a severe drought the small, soft seeds ran out and only large, hard seeds were left. Birds with deeper beaks could crack these seeds. Many birds with shallow beaks starved. When the survivors bred, the chicks had a greater average beak depth than the previous generation.

   (a)

   What type of variation is beak depth in these finches?

   [1 mark]

   • ADiscontinuous variation, because every bird falls into one of a few clear groups
   • BEnvironmental variation only, because beak depth cannot be inherited
   • CThere is no variation, because all the birds are the same species
   • DContinuous variation, because the values form a range with most birds near the middle

   (b)

   Which sequence correctly describes natural selection?

   [1 mark]

   • AOrganisms compete; they change to fit their needs; the changes are passed on to their young
   • BThe environment changes; all organisms in the population adapt; all survive
   • CVariation exists; organisms compete; better-adapted ones survive and reproduce; their features are passed on
   • DThe strongest organism kills the rest; it is the only one to reproduce

   (c)

   Explain why the average beak depth of the finches increased in the next generation.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Students want to estimate the number of daisy plants in a school field that measures 80 m by 40 m. They place ten quadrats, each 1 m by 1 m, at different positions in the field and count the daisies inside each one. The counts are 4, 7, 3, 6, 5, 8, 2, 5, 6 and 4.

   (a)

   Calculate the mean number of daisies per quadrat and use it to estimate the total number of daisies in the field.

   [3 marks]

   (b)

   Evaluate the students' method and suggest two improvements to make the estimate more reliable.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   The Arabian oryx is an antelope adapted to life in the desert. It was hunted so heavily that the last wild oryx were killed in 1972. Zoos bred oryx in captivity, and from the 1980s groups were released into protected reserves on the Arabian Peninsula. The programme costs a lot of money, and rangers must guard the herds. Some people argue that the money could protect more species if it was spent on protecting habitats.

   (a)

   Explain why a species such as the Arabian oryx can become extinct.

   [6 marks]

   (b)

   Discuss and evaluate captive breeding and reintroduction programmes such as the one for the Arabian oryx.

   [6 marks]

   Total for question 4: 12 marks

End of questions