Question

climate and the carbon cycle
before the presence of fungi and land plants, earth’s atmosphere was very different than what it is now. it contained high levels of carbon dioxide, which kept earth’s surface temperature higher than it is today. the early appearance of fungi and land plants are linked to many changes, including changes to the chemical composition of the atmosphere. these changes made life possible for a wide range of new organisms.
these new organisms could perform functions that more primitive organisms could not. plants used the abundant carbon dioxide, combined with water, to create energy for cellular processes through photosynthesis. photosynthesis released oxygen into an atmosphere that typically contained only 5% oxygen gas. lichen, a type of fungi, lived symbiotically with photosynthesizing organisms, like algae. they produced acids that dissolved the rocks upon which they lived, releasing calcium deposits. these deposits, carried toward the ocean by rainfall, would bond with dissolved carbon dioxide and water (carbonic acid) and eventually create calcium carbonate. this prevented carbon atoms from forming carbon dioxide and therefore reduced the amount of carbon dioxide in the atmosphere of the prehistoric period. figure 1 illustrates this process.
figure 1.
lichen/fungi/algae
complex
which two statements are correct about interactions described in the passage?
a. lichen dissolving rocks is an interaction between the biosphere and the geosphere.
b. carbon dioxide reacting with calcium is an interaction between the atmosphere and biosphere.
c. fungi and algae living together is an interaction between the geosphere and hydrosphere.
d. plants using carbon dioxide for photosynthesis is an interaction between the biosphere and atmosphere.
e. algae releasing oxygen for land organisms is an interaction between the hydrosphere and geosphere.

Explanation:

• For option A: Lichen (biosphere) dissolving rocks (geosphere) is a biosphere - geosphere interaction. This matches the description in the passage where lichen produces acids to dissolve rocks.
• For option D: Plants (biosphere) using carbon dioxide (atmosphere) for photosynthesis is a biosphere - atmosphere interaction. The passage states plants use abundant carbon dioxide for photosynthesis.
• Option B: Carbon dioxide reacting with calcium involves atmosphere (CO₂) and geosphere (calcium from rocks, part of geosphere), not biosphere. So B is wrong.
• Option C: Fungi and algae living together are both part of biosphere, not geosphere - hydrosphere. So C is wrong.
• Option E: Algae (biosphere) releasing oxygen for land organisms (biosphere) and oxygen is in atmosphere, not hydrosphere - geosphere. So E is wrong.

Answer:

A. Lichen dissolving rocks is an interaction between the biosphere and the geosphere, D. Plants using carbon dioxide for photosynthesis is an interaction between the biosphere and atmosphere