Answer:
Plants and animals assimilate carbon-14 from carbon dioxide throughout their life. When they die, they stop exchanging carbon with the biosphere and their carbon-14 content begins to decrease at a rate determined by the law of radioactive decay.
Radiocarbon dating is basically a method designed to measure residual radioactivity.
Explanation:
Carbon-14 is a weakly radioactive carbon isotope; It is also known as radiocarbon, and is an isotopic stopwatch.
Radiocarbon dating is only applicable to organic materials and some inorganic materials (not applicable to metals).
Proportional gas counting, liquid scintillation counting, and accelerator mass spectrometry are the three main methods of radiocarbon dating.
The radiocarbon, or carbon-14, is an isotope of the carbon element that is unstable and weakly radioactive. The stable isotopes are carbon-12 and carbon-13.
Carbon 14 is continuously formed in the upper atmosphere by the effect of cosmic ray neutrons on nitrogen-14 atoms, rapidly oxidizing in the air to form carbon dioxide and entering the global carbon cycle.
Accelerator mass spectrometry (AMS) is a modern method of radiocarbon dating that is considered the most efficient way to measure the radiocarbon content of a sample. In this method, the content of carbon-14 is measured directly in relation to carbon-12 and carbon-13 present. The method does not take into account beta particles, but the number of carbon atoms present in the sample and the proportion of the isotopes.
Answer:
Transport proteins play a role in both active and passive transport to move molecules across the plasma membrane
Mammalian fertilization comprises sperm migration through the female reproductive tract, biochemical and morphological changes to sperm, and sperm-egg interaction in the oviduct. Recent gene knockout approaches in mice have revealed that many factors previously considered important for fertilization are largely dispensable, or if they are essential, they have an unexpected function. These results indicate that what has been observed in in vitro fertilization (IVF) differs significantly from what occurs during “physiological” fertilization. This Review focuses on the advantages of studying fertilization using gene-manipulated animals and highlights an emerging molecular mechanism of mammalian fertilization.
This is correct, because aerobic is more efficient than anaerobic, making it preferable. Cellular respiration is energetically more efficient than anaerobic respiration.
<h3>Cellular respiration and anaerobic respiration </h3>
Cellular respiration refers to the generation of energy in the form of ATP in presence of oxygen.
Conversely, anaerobic respiration generates energy (ATP) in absence of oxygen.
Cellular respiration is an energetically more efficient pathway than anaerobic respiration, thereby facultative organisms generate ATP by cellular respiration when it is possible.
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