For example, Charles Darwin predicted the existance of a moth in Madagascar based on the size and shape of a flower he saw there. The moth was actually discovered about 40 years later. The common snapdragons that many people plant in their gardens are designed for a bumblebee of just the right weight to trip the opening mechanism. Their reproductive strategy is to produce lots of pollen in hopes that some makes it to the female. These plants expend much energy in making pollen.
Many plants depend on animals to spread their pollen.
This is a mutualistic relationship where the plant and the pollinator benefit each other. The hypothetical evolution of pollination and angiosperms is tied together. Early gymnosperms and angiosperms were wind-pollinated. Like modern gymnosperms, the ovule exuded droplets of sap to catch pollen grains. Insects became dependent on this food source and started carrying pollen from plant to plant.