Answer:
A. 17,100
Explanation:
The half life of carbon-14 is around 5,700 years. When the shell contains 50% of its original carbon-14, 5,700 years have passed. 25% means another 5,700 years have passed, meaning 11,400 years in total have passed. 12.5% means another 5,700 years have passed, meaning 17,100 years have passed in total.
Energy can be converted from one form to another, but it cannot be created or destroyed in ordinary chemical or physical means. It states that matter can be neither created nor destroyed in ordinary chemical or physical changes.
Answer:
The ability of caffeine to inhibit adenosine receptors, plays a very important role in heightened alertness and sleeplessness.
Explanation:
"<em><u>Caffeine</u></em>" (<em>1,3,7-trimethylxanthine</em>) is an alkaloid obtained from plants. It has a chemical formula of C8H10N4O2.
Caffeine is generally <em>hydrophillic</em> but sufficiently <em>lipophilic</em> to pass through all biological membranes and readily cross the blood-brain barrier.
Therefore can bind with the adenosine receptors. Due to the blocking of adenosine inhibitory effects through its receptors held by paraxanthine and caffeine, it indirectly affects the release of <u>norepinephrine, dopamine, acetylcholine, serotonin, glutamate</u> e.t.c.
The release of the above-mentioned hormones have a great impact on the heightened alertness of the body, especially <em>dopamine</em> and <em>serotonin</em>.
Answer:
cell wall,vacoule,and plastids are not present
The Galapagos islands. the grants studied finches on these islands to learn more about evolution
