Question

Study the following statements and pick up the incorrect statements.
I. Oriented locomotor movement of an organism towards or away from the direction of light is called photokinesis.
II. The influence of light on non-directional movement of organisms is called phototaxis.
III. UV-B and UV-C rays are more harmful than UV-A rays.
IV. Photoperiod influences the migration of birds.

• A. I, II
• B. III, IV
• C. II, IV
• D. I, III

Hint:

Differentiate between 'taxis' and 'kinesis': \textbf{Taxis:} Directed movement towards or away from a stimulus (e.g., phototaxis is directional movement due to light). \textbf{Kinesis:} Undirected change in activity rate (speed or turning frequency) in response to stimulus intensity (e.g., photokinesis is non-directional movement due to light intensity). \textbf{UV Radiation:} UV-C>UV-B>UV-A in terms of harmfulness. \textbf{Photoperiod:} A major environmental signal for seasonal biological events like bird migration.

Answer 1

The Correct Option is A

Step 1: Analyze Statement I)
Statement I says: "Oriented locomotor movement of an organism towards or away from the direction of light is called photokinesis."
Taxis refers to a directional movement or orientation of an organism in response to a stimulus. Phototaxis specifically refers to directional movement towards (positive phototaxis) or away from (negative phototaxis) a light source.
Kinesis refers to a non-directional, undirected movement in response to a stimulus, where the organism's speed or rate of turning changes in response to stimulus intensity, but not its direction. Therefore, the oriented (directional) movement in response to light is called phototaxis, not photokinesis. Statement I is Incorrect. Step 2: Analyze Statement II)
Statement II says: "The influence of light on non-directional movement of organisms is called phototaxis."
As explained above, phototaxis is a directional movement in response to light.
The non-directional movement influenced by light is called photokinesis.
Therefore, Statement II is Incorrect. Step 3: Analyze Statement III)
Statement III says: "UV-B and UV-C rays are more harmful than UV-A rays." Ultraviolet (UV) radiation is categorized into UV-A, UV-B, and UV-C based on wavelength.
UV-A has the longest wavelength and is less harmful, primarily causing skin aging.
UV-B has a medium wavelength and is responsible for most sunburns and skin cancer.
UV-C has the shortest wavelength and is the most energetic and harmful, but it is almost entirely absorbed by the Earth's ozone layer and atmosphere before reaching the surface.
Therefore, UV-B and UV-C rays are indeed more harmful than UV-A rays. Statement III is Correct. Step 4: Analyze Statement IV)
Statement IV says: "Photoperiod influences the migration of birds." Photoperiod (the duration of daylight in a 24-hour cycle) is a crucial environmental cue for many biological processes in animals and plants, including seasonal migration in birds. Changes in photoperiod signal the onset of seasons, triggering physiological and behavioral changes like preparing for migration.
Therefore, Statement IV is Correct. Step 5: Identify the incorrect statements
Based on the analysis:
Statement I is Incorrect.
Statement II is Incorrect.
Statement III is Correct.
Statement IV is Correct.
The question asks to pick up the incorrect statements. The incorrect statements are I and II. Step 6: Choose the correct option
The option that contains both I and II is (1).