A biology lab group investigated how wind speed affects the rate of water loss in *Phaseol… — ACT

A biology lab group investigated how wind speed affects the rate of water loss in *Phaseolus vulgaris* (common bean) plants. The group initially hypothesized that transpiration rates would increase continuously and linearly across all wind speeds due to the constant removal of the boundary layer of water vapor.

They recorded the transpiration rates at different wind speeds in a wind tunnel and compiled the data in the table below:

Wind Speed ( $\text{m/s}$ )	Transpiration Rate ( $\text{mg}\cdot\text{dm}^{-2}\cdot\text{min}^{-1}$ )
$0.0$	$1.8$
$1.0$	$3.5$
$2.0$	$5.2$
$3.0$	$6.8$
$4.0$	$7.0$
$5.0$	$6.9$

Based on the results in the table, which of the following statements represents the most accurate modification of the group's initial hypothesis?

A
The transpiration rate is completely unaffected by wind speed and remains constant across all tested speeds.
B
The transpiration rate decreases continuously as wind speed increases because the wind cools the leaf surface.
The transpiration rate increases with wind speed up to a threshold of approximately $3.0\text{ m/s}$ , after which it plateaus and remains relatively constant.Cevap
D
The transpiration rate increases linearly and continuously across all wind speeds, with no upper limit.

Cevap

The transpiration rate increases with wind speed up to a threshold of approximately

3.0\text{ m/s}

, after which it plateaus and remains relatively constant.

The correct option correctly describes the two distinct phases of the data trend: a steady rise in the transpiration rate up to about

3.0\text{ m/s}

, followed by a plateau where the rate remains constant. This modification reflects the physical limits of the system, such as stomatal closure in high winds, which prevent a continuous linear increase.

Adım Adım Çözüm

Analyze the change in transpiration rate values as wind speed increases from

0.0\text{ m/s}

3.0\text{ m/s}

The rate increases steadily from

1.8

6.8\text{ mg}\cdot\text{dm}^{-2}\cdot\text{min}^{-1}

This establishes that there is an initial positive relationship between wind speed and transpiration rate, supporting the direction of the initial hypothesis in this range.

Analyze the transpiration rate values as wind speed increases further from

3.0\text{ m/s}

5.0\text{ m/s}

The rate changes minimally from

6.8

7.0

and then slightly drops to

6.9\text{ mg}\cdot\text{dm}^{-2}\cdot\text{min}^{-1}

This shows that the rate levels off and no longer increases, indicating a threshold effect or plateau.

Combine these observations to formulate a modified hypothesis that matches the overall data trend.

The rate increases initially but plateaus after a threshold of approximately

3.0\text{ m/s}

A modified hypothesis must reflect both trends observed in the experimental data to be scientifically valid.

Anahtar Kavram

Formulating and Modifying Hypotheses

Tahmini Süre:1m 30s

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