<span><em>They tell us how life evolved and adapted to different environments and global changes throughout the Earth's development</em>
<em> Hope this helps:)</em>
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I believe Tom is mot likely suffering from the post traumatic stress disorder.Post traumatic stress disorder is the mental health condition that is triggered by a terrifying event-either experiencing it or witnessing it. Symptoms may include flashbacks, nightmares and severe anxiety, as well as uncontrollable thoughts about the event.
The main reason that most farmers use stem cuttings rather than just planting a seed is that a tree's genetic variation will occur. The seeds of many fruit trees tend to vary differently from the parent, because seeds themselves are produced by sexual reproduction (i.e they receive genes from a male and female to form). As they are a cross from two sets of genes, many fruit trees are not “true to seed”. Their seeds will produce a generally different variety of tree from the parent. When using stem cuttings, it's almost like a cloning process.
