Fig. 1 shows an investigation in which scientists release marked beetles into two grassland areas, then recapture beetles after a dry summer. The beetles va...
Question 1 Report
Fig. 1 shows an investigation in which scientists release marked beetles into two grassland areas, then recapture beetles after a dry summer. The beetles vary in water loss because their body coverings are controlled by different alleles.
(a) Describe one characteristic that could vary between individual beetles. [1]
(b) Explain why beetles that lose less water may become more common after several dry summers. [3]
(c) Give two features of the investigation that would make its conclusion more reliable. [2]
Answer Details
(a) One characteristic that could vary is body colour. Body size, rate of water loss and thickness of body covering are also acceptable. [1]
(b) Beetles that lose less water are more likely to survive drought. They then reproduce more successfully and pass the alleles associated with lower water loss to their offspring. Over generations, these alleles become more frequent, so such beetles become more common. [3]
(c) Reliability could be improved by using many beetles and repeating the investigation in several areas or years. Random sampling and comparison with a wetter control area are also valid. [2]
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