Evidence for climate change and its causesEdexcel International A Level Biology: Mind map

Exam questions on Evidence for climate change and its causes

1. A research team is drilling a core of ice from the Antarctic ice sheet. The ice was formed from compacted snowfall laid down year after year, and it contains tiny bubbles of air trapped when each layer of snow was buried. The team wants to reconstruct how the concentration of carbon dioxide in the atmosphere has changed over hundreds of thousands of years.
   Describe how the team can use the ice core to find the carbon dioxide concentration of the atmosphere at different times in the past.2 marks
2. Ecologists in northern England have taken a vertical core from a peat bog. The peat is waterlogged and acidic, and it has built up slowly over about 10 000 years. Microscopy of samples from different depths shows many pollen grains from plants that grew in the area when each layer formed. The deepest layers contain mainly pollen of dwarf birch and other plants that tolerate cold, while the shallowest layers contain mainly pollen of oak, hazel and elm.
   Deduce what the pollen record suggests about the change in climate in the area, and suggest one reason why this conclusion may not be fully reliable.2 marks
3. Dendrochronologists are studying oak trees. They have measured the width of each annual ring in a living oak that is 220 years old. They have also measured rings in oak beams from medieval buildings and in preserved oak trunks dug from river sediment. Some of these samples are older than any living tree. They want to build a record of growing conditions covering the last 1000 years.
   Explain how dendrochronology can be used to build a record of past growing conditions covering 1000 years from trees that are much younger than this.3 marks