▶️ Answer/Explanation
Phototropism is a biological phenomenon where an organism, typically a plant, grows in response to a light stimulus. The term is derived from “photo” meaning light and “tropism” meaning a turning or growth movement. In plants, shoots generally exhibit positive phototropism by growing toward the light source to maximize photosynthesis. This occurs because plant hormones called auxins accumulate on the shaded side of the stem, causing those cells to elongate faster and bend the plant toward the light. Options (C) and (D) describe metabolic processes like respiration and photosynthesis, while option (A) describes geotropism (or gravitropism).
✅ Answer: (B)
▶️ Answer/Explanation
The pancreas is a dual-function organ acting as both an exocrine and endocrine gland. Within the endocrine portion, specific clusters of cells known as the Islets of Langerhans are responsible for blood sugar regulation. The alpha cells ($\alpha$-cells) in these islets secrete glucagon when blood glucose levels are low. Glucagon then travels to the liver to trigger the breakdown of glycogen into glucose. In contrast, beta cells secrete insulin to lower blood sugar. Therefore, the pancreas is the primary site of glucagon production.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
Blood glucose levels are regulated via negative feedback. When glucose levels fall, the pancreas detects this change and secretes the hormone glucagon. Glucagon then travels to the liver, triggering the breakdown of stored glycogen back into glucose to raise blood sugar levels. Option (A) is incorrect because glucose is converted into glycogen for storage, not glucagon (which is a hormone). Option (B) is incorrect because the pancreas, not the liver, releases insulin. Option (C) is false as the pancreas actively responds to high glucose by secreting insulin.
✅ Answer: (D)
✅ Answer: (D)