Introduction: The task involves the application of three styles of definitions; parenthetical, sentence, and expanded. The objective is to comprehend how the audience and purpose dictate the requirement for definition, distinguish between the levels of detail in definition, and choose the appropriate level of detail based on the scenario.
Term: Phototropism
Target Audience and Situation: Third year Biology students in a Plant Biology course.
Parenthetical Definition: Phototropism is the growth of an organism in response to light.
Sentence Definition: Phototropism is a growth response by an organism towards or away from a light source. It is a biological phenomenon that occurs in plants and some other organisms, and is important for their survival and adaptation to their environment.
Expanded Definition:
History and Background
The term “phototropism” was first used in the late 1800s to describe the growth response of plants towards light. Phototropism is a type of tropism, which is a general term for growth or turning movements in response to a stimulus. Phototropism is essential for plants to optimize their exposure to light, which is required for photosynthesis and overall growth.
Negation
Phototropism is the growth of an organism towards or away from a light source. The negation of this term, then, is the absence of a growth response towards or away from a light source. This could occur if the organism is unable to detect the presence or absence of light or if it is unable to generate a response to it. In either case, the absence of a response would indicate a lack of phototropism. This could be due to a variety of factors, such as a lack of the necessary photoreceptors or signalling pathways, an inability of the organism to respond to the stimulus, or a lack of sufficient resources to generate a response.
Operating Principle
Phototropism is controlled by photoreceptors in the organism that detect the presence and direction of light. This information is then transduced into biochemical signals that cause the growth of the organism towards or away from the light source. The exact mechanism by which this occurs depends on the organism and the type of phototropism, but it typically involves changes in hormone levels and changes in the orientation of the organism’s cells.
Example
An example of phototropism is how a plant stem grows towards a light source. The photoreceptors in the stem detect the direction of light and signal the cells on the side of the stem away from the light to elongate. This bending of the stem towards the light source allows the plant to optimize its exposure to light for photosynthesis.
Work Cited
Julie A. Zickel, Phototropism, Editor(s): Mark D. D. Brown, Plant Development: Physiology, Molecular Biology, and Biotechnology Applications, Wiley-Blackwell, 2011, Pages 29-33, ISBN 9781405185869
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