Which radioactive isotope is commonly used for dating relatively recent fossils (up to about 50,000 years old)?
A. Carbon-14
B. Rubidium-87
C. Potassium-40
D. Uranium-238
Answer: Option A
Solution (By JKExamLibrary)
Carbon-14 (radiocarbon) dating is used to determine the age of organic materials up to about 50,000 to 60,000 years old. Living organisms absorb Carbon-14 from the atmosphere. When they die, absorption stops, and the Carbon-14 decays at a known rate (half-life of 5,730 years). By measuring the remaining Carbon-14, the age of the fossil can be calculated.
Explanation:
The urinary bladder is a muscular sac that temporarily stores urine received from the kidneys via the ureters, until micturition. The urethra drains urine to the exterior.
Explanation:
Phototropism (positive in shoots) is caused by the migration of auxin to the shaded side of the shoot, promoting cell elongation more on that side, causing the shoot to bend towards light. This asymmetric auxin distribution was demonstrated by Went's experiments. Auxin is sensitive to light and moves laterally. This is a growth response to directional light.
Explanation:
Bile juice is continuously secreted by the liver. It is stored and concentrated in the gall bladder and released into the duodenum (first part of the small intestine) when food enters. Bile contains bile salts (like bilirubin and biliverdin) which are crucial for the emulsification of fats, breaking them into smaller micelles for easier digestion by lipases.
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