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Explanation:
The scarcity of natural examples is due to the fact that there are population controls due to a limiting amount of resources such as food, light, shelter, water as well as to factors such as predation, climatic change, and disease.
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point mutation, change within a gene in which one base pair in the DNA sequence is altered. Point mutations are frequently the result of mistakes made during DNA replication, although modification of DNA, such as through exposure to X-rays or to ultraviolet radiation, also can induce point mutations
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The phloem carries important sugars, organic compounds, and minerals around a plant. Sap within the phloem simply travels by diffusion between cells and works its way from leaves down to the roots with help from gravity. The phloem is made from cells called 'sieve-tube members' and 'companion cells'.