Question 19N.2.HL.TZ0.e
| Date | November 2019 | Marks available | [Maximum mark: 3] | Reference code | 19N.2.HL.TZ0.e |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Evaluate | Question number | e | Adapted from | N/A |
The black-legged tick (Ixodes scapularis) is an arthropod which sucks blood from humans and other mammals. It is encountered mainly in wooded and semi-wooded areas. Some ticks can be infected by the bacterium Borrelia burgdorferi. When a tick bites a human, the bacterium is often introduced, causing Lyme disease. Lyme disease is a public health problem in North America and, if left untreated, can cause important neurological impairment. The diagram represents the two-year life cycle of a tick.
[Source: Cary Institute of Ecosystem Studies / Leslie Tumblety]
Scientists fear that global warming will change the distribution range of ticks.
The graphs show the developmental stages of ticks throughout seasons in a densely human-populated area of south-eastern Canada, surrounded by woods (circled on the map). Values are already established for 2000 and are predicted for 2080.
[Source: reprinted from International Journal for Parasitology, 36(1), N.H. Ogden, A. Maarouf, I.K. Barker, M. Bigras-Poulin,
L.R. Lindsay, M.G. Morshed, C.J. O’Callaghan, F. Ramay, D. Waltner-Toews, D.F. Charron, Climate change
and the potential for range expansion of the Lyme disease vector Ixodes scapularis in Canada,
63–70, Copyright (2006), with permission from Elsevier]
Evaluate the effect of the change in distribution of the different life stages of ticks on the spread of Lyme disease in south-eastern Canada.
[3]
a. nymphs present through most of year/longer period/from March to November/through spring and summer «so more risk of infection» ✔
b. more adults in winter/in January/February so more risk of infection then ✔
c. infection will be possible through more/most months of/throughout the year ✔
d. Lyme disease likely to/will increase ✔
