Question

Most seeds are dull-coloured, and many of them taste quite bitter. Some are even poisonous. Most fruits are green and sour when un-ripe, and brightly coloured and sweet when ripe. How might you explain these facts from the point of view of the evolution of the plants themselves?

Answer 1

In this case, we are observing a evolutionary pathway called plant defenses against herbivory or host plant resistance. This phenomenon consist in a series of evolutionary adaptations of plants to improve their survival and reproduction by reducing the impact of herbivory. Plants can perceive tactile stimuli and can use various strategies to defend against damage caused by herbivores. Many plants produce secondary metabolites (allelochemicals) that influence behavior, growth or survival against herbivores. These chemical defenses can act as toxins against herbivores. Just as we observe in this population of plants, that developed a type of poison.

Another approach is to make the herbivores to eat non-essential parts, as we can see the fruit in some cases become sweet and remember that the fruit contains the seed inside. Once the herbivore eats it, it will spread the fruit to other zone where the plant can grow again. On the other hand we have the dull coloration that allows plants to blend into the environment or the bitter taste which is not preferred by taster animals.