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BIOLOGY, M4 EQ-Bank 6

The graph below shows the concentration of \(\ce{CO2}\) in the earth's atmosphere over the last 800 years.

  1. How would scientists obtain these historical levels of \(\ce{CO2}\)?   (1 mark)

  2. Explain the shape of the graph over the 800 years of data presented.   (3 marks)

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a.   Data would be obtained by gas analysis within ice cores.

b.   Graph shape over the past 800 years:

  • Atmospheric levels of \(\ce{CO2}\) were very steady between the period 1200-1800 at approximately 280 ppm.
  • In the period 1800-2000, \(\ce{CO2}\) levels increased exponentially from 280 ppm to 370 ppm.
  • This increase coincided with industrialisation which saw the widespread use of fossil fuels like coal, oil, and natural gas for energy.
  • The use of these energy sources released large amounts of (\ce{CO2}\) into the atmosphere and is regarded as a major contributing factor to rise in atmospheric \(\ce{CO2}\) levels over this period.
Show Worked Solution

a.   Data would be obtained by gas analysis within ice cores.

b.   Graph shape over the past 800 years:

  • Atmospheric levels of \(\ce{CO2}\) were very steady between the period 1200-1800 at approximately 280 ppm.
  • In the period 1800-2000, \(\ce{CO2}\) levels increased exponentially from 280 ppm to 370 ppm.
  • This increase coincided with industrialisation which saw the widespread use of fossil fuels like coal, oil, and natural gas for energy.
  • The use of these energy sources released large amounts of (\ce{CO2}\) into the atmosphere and is regarded as a major contributing factor to rise in atmospheric \(\ce{CO2}\) levels over this period.

BIOLOGY, M4 EQ-Bank 5

Scientists analyse the ratio of \(\ce{^{16}O}\) to \(\ce{^{18}O}\) isotopes in various geological samples to reconstruct past climatic conditions.

  1. Describe one method used to obtain oxygen isotope data from ancient samples.   (1 mark)

  2. Explain how the relationship between \(\ce{^{16}O}\) and \(\ce{^{18}O}\) ratios provides evidence of past changes in ecosystems.   (3 marks)

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a.   Scientists analyse gas trapped within ice cores.

b.   \(\ce{^{16}O : ^{18}O}\) ratios

  • The ratio of \(\ce{^{16}O : ^{18}O}\) in geological samples reflects past temperature and precipitation patterns, which are crucial factors in shaping ecosystems.
  • During warmer periods, there is a higher proportion of the heavier \(\ce{^{18}O}\) isotope in precipitation.
  • During cooler periods, there is a relative increase in lighter \(\ce{^{16}O}\).
  • These isotopic signatures allow scientists to reconstruct past climate conditions and infer associated ecosystem changes.
Show Worked Solution

a.   Scientists analyse gas trapped within ice cores.

b.   \(\ce{^{16}O : ^{18}O}\) ratios

  • The ratio of \(\ce{^{16}O : ^{18}O}\) in geological samples reflects past temperature and precipitation patterns, which are crucial factors in shaping ecosystems.
  • During warmer periods, there is a higher proportion of the heavier \(\ce{^{18}O}\) isotope in precipitation.
  • During cooler periods, there is a relative increase in lighter \(\ce{^{16}O}\).
  • These isotopic signatures allow scientists to reconstruct past climate conditions and infer associated ecosystem changes.

BIOLOGY, M4 EQ-Bank 1 MC

Which of the following statements about radiometric dating is correct?

  1. It can only be used to date organic materials.
  2. It is based on the constant decay rate of radioactive isotopes.
  3. It provides the relative age of fossils, not the absolute age.
  4. It is most accurate for dating materials less than 1,000 years old.
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\(B\)

Show Worked Solution

Consider each statement.

  • Option A: Incorrect. Radiometric dating can be used on both organic and inorganic materials.
  • Option B: Correct. Radiometric dating is based on calculations of the ratio of parent to daughter isotopes in a process of constant decay.
  • Option C: Incorrect. Radiometric dating actually provides the absolute age of materials, not just relative age. 
  • Option D: Incorrect. While some radiometric methods (like carbon-14 dating) are useful for relatively recent materials, many radiometric techniques can date materials billions of years old. 

\(\Rightarrow B\)

BIOLOGY, M4 EQ-Bank 25

The charts below show data compiled from ice core drilling sites located in Greenland and Antarctica.
 

How does the data provide evidence that the drastic change in gas concentration is NOT part of a natural cycle?   (4 marks)

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  • The concentrations of carbon dioxide and methane remained stable until around 1750. From 1750 to the present, methane levels increased by 200% and carbon dioxide by 40%.
  • This rise is mainly due to the Industrial Revolution, which began in 1760 and brought significant advances in manufacturing and agriculture.
  • Deforestation and the burning of fossil fuels, both of which have accelerated over time, have driven the increase in these gases.
  • While methane is partly linked to human activities like farming, it also originates from natural sources such as volcanic eruptions and organic matter breakdown.
  • The growing global population has intensified these processes, further contributing to methane emissions.
Show Worked Solution
  • The concentrations of carbon dioxide and methane remained stable until around 1750. From 1750 to the present, methane levels increased by 200% and carbon dioxide by 40%.
  • This rise is mainly due to the Industrial Revolution, which began in 1760 and brought significant advances in manufacturing and agriculture.
  • Deforestation and the burning of fossil fuels, both of which have accelerated over time, have driven the increase in these gases.
  • While methane is partly linked to human activities like farming, it also originates from natural sources such as volcanic eruptions and organic matter breakdown.
  • The growing global population has intensified these processes, further contributing to methane emissions.