Question

1. increased levels of atmospheric co₂ result in the greenhouse effect and thus affect global climatic warming. the graph below shows the effect of these changes on photosynthesis. which of the following statements about these processes is false? (a) for most plants, temperatures over 40°c reduce photosynthesis. (b) at temperatures below 20°c, high atmospheric co₂ concentrations reduce photosynthesis to values below those seen for plants growing in normal co₂ concentrations. (c) one result of increased levels of atmospheric co₂ will be to increase rates of photosynthesis in most plants. (d) at high co₂ concentrations, the highest rates of photosynthesis are measured at temperatures between 30° and 35°c. (e) co₂ concentration is normally rate - limiting for photosynthesis. 92. place the following events in a logical order: i. atmospheric co₂ increases ii. warmer ocean iii. warmer temperature iv. less co₂ uptake by the oceans (a) i→ii→iii→iv (b) ii→iv→i→iii (c) iv→ii→i→iii (d) ii→iii→i→iv (e) iii→ii→i→iv

Explanation:

Step1: Analyze statement A

From the graph, for both high and normal CO₂ levels, photosynthetic rate drops above 40°C, so this is true.

Step2: Analyze statement B

Looking at the graph, at temperatures below 20°C, high - atmospheric CO₂ concentrations have a higher photosynthetic rate than normal CO₂ concentrations, so this statement is false.

Step3: Analyze statement C

The graph shows that in general, high atmospheric CO₂ leads to higher photosynthetic rates, so this is true.

Step4: Analyze statement D

The peak of the high - CO₂ curve is between 30°C and 35°C, so this is true.

Step5: Analyze statement E

Typically, CO₂ is a rate - limiting factor for photosynthesis, which is consistent with general knowledge and the graph's trend, so this is true.

Step6: Analyze question 92

When atmospheric CO₂ increases (I), it causes the temperature to rise (III). A warmer temperature leads to a warmer ocean (II). Warmer oceans can hold less CO₂, resulting in less CO₂ uptake by the oceans (IV). So the order is I→III→II→IV, but this is not an option. The correct causal chain is that an increase in atmospheric CO₂ (I) causes a warmer temperature (III), which warms the ocean (II), and a warmer ocean has less CO₂ uptake (IV), i.e., I→III→II→IV. But if we consider the most logical sequence from the options based on the feedback - loop nature, when the ocean warms (II), it takes up less CO₂ (IV), which increases atmospheric CO₂ (I), and then warms the temperature further (III). So the order is II→IV→I→III.

Answer:

1. B
2. B