The interplay between the fruit-eating primates and the tropical fruit trees is an example of coevolution, where species adapt to each others’ needs over millions of years. The plants have an interest in their fruit being eaten when the seeds are ready to be dispersed, and for the animals the value of a fruit is greater when it contains more sugar and nutrients. An unripe banana for instance contains mostly starch.
Prof. Matthias Laska:
”This adaptation goes back some fifty thousand years, when the first primates appeared. Initially they ate mostly insects, before eventually trying fruit and vegetables. Some fruit didn’t want to be eaten, so they developed toxic substances. Others acquired better and better odours that signaled energy-rich sugar and nutrients.”
Seed is an embryonic plant enclosed in a protective outer covering. The formation of the seed is part of the process of reproduction in seed plants. Seeds have been an important development in the reproduction and success of gymnosperms and angiosperms plants, that now dominate biological niches on land.
The term "seed" also has a general meaning of anything that can be sown, e.g. "seed" potatoes (tubers), "seeds" of corn or sunflower "seeds".
Many structures commonly referred to as "seeds" are actually dry fruits. Different groups of plants have other modifications, the so-called stone fruits (such as the peach) have a hardened fruit layer (the endocarp) fused to and surrounding the actual seed.
Nuts are the one-seeded, hard-shelled fruit of some plants with an indehiscent seed (acorn, hazelnut).