I scientist studies and analyzes facts.
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Pioneer species are found in area's undergoing secondary succession. For example ecosystems being established by: reducing a fire, deforestation; which quickly colonize open spaces supported by vegetation.
One fourth means (one half) of (one half) .
So the 18 months must be two half-lifes.
The half-life of this particular isotope is 9 months.
Homologous chromosomes pair during Prophase I of Meiosis I.
