Hello
It is because ur mouth is a dark and warm place which is the perfect environment for bacteria to grow and survive. It doesn’t matter if u brush it really well on ur tounge there and groves in ur tounge where the toothbrush bristles cannot reach and clean so that is where the bacteria lives.
Hope this helps
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For evolution to occur:
There must be genetic variation in a population. This provides variation on which natural selection can act. Then natural selection can act by selecting those species which are better adapted to the environmental conditions. Over time those animals that are best suited to the environment only will survive and reproduce. Those organisms successful genes will be preserved and eventually the gene frequency in the population will change, changing the overall characteristics of a population. This is how evolution occurs.
Answer: A - Uptake of food and water by plants
The xylem vessels in the roots of the plants use the mechanism of capillary action and work against gravity to pull water molecules and nutrients from the soil and carry them upwards to the leaves of the plant to provide nourishment to the plant.