Why are some berries poisonous?

Question

In my understanding, the evolutional function of berries is to be eaten and pood out somewhere else, so that the seeds of the plant spread. Is this so? Then why are some berries poisonous?

Answer 1

Poisons in plant fruit happen while the fruit is developing. Nonripe is poisonous to stop animals from eating it and releasing the seeds before ripening. Poisons in ripe fruit may be there in order for animals to move further away from the parent plant before releasing the seeds. Therefore, causing the parent plant to make offspring (more plants of itself). Another reason ripe fruit may be poisonous is that it stays longer in animals' systems before being released so the seeds are far away from the parent plant.