Answer:
Electrons are arranged in layers
Explanation:An atom is solid and the Nucleus is at the center of an atom+ it isn't possible for electrons to form layers
Answer: Their pollen is dispersed by wind.
Explanation:
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:
<em><u>D. The first flowering plants were introduced toward the end of the Mesozoic era.</u></em>
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Explanation:
Following the Paleozoic Era, the Mesozoic Era or <em>Age of Conifers</em> began approximately 250 million years ago. This major geological era brought about the ancestors of many of the plant and animal groups still in existence today.
The Mesozoic era is marked by 3 divisions:
- the Triassic Period,
- the Jurassic Period,
- and the Cretaceous Period.
Animals and plants slowly recovered after the mass extinction in the Permian-Triassic extinction that led to the eradication of most aquatic marine species. They evolved to exploit varying niches in their environment, leading to a boom in terrestrial animals. Over time the planet's increasingly warm climate, abundant in atmospheric oxygen and carbon dioxide, contributed to the growth of diverse megaflora, that rapidly dominated the planet's terrestrial biosphere.
By the end of the <em>Mesozoic Era</em>, in the Cretaceous period, flowering plants (angiosperms) largely replaced the dominant seed ferns of the <em>Triassic</em>, and the conifers, cycads and gymnosperms of the <em>Jurassic</em>.
<em>Varied dispersal mechanisms in angiosperms co-evolved with the evolution of certain types of fauna. Plants used animal life, including herbivorous reptiles and early mammal-like species to disperse large seeds.</em>
