How did plants come to "know" there were animals alive that would eat it's fruit when it first produced this fruit?
closed as unclear what you're asking by David, anongoodnurse, kmm, another 'Homo sapien', canadianer May 11 '17 at 7:14
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The plant does not "know" there are animals. It is just that plants, that accidentally evolved (due to mutations) a fruit that attracts animals (which can spread its seeds etc.) had an advantage over plants that did not have them. The disadvantaged plants just became extinct after a while. And you must be aware that the first fruits were rather "pre-fruits", but already a selective advantage to their bearers.
How did a plant know there were animals to have have spines, prickling hairs, acidic leaves, soapy sap, stings, wooden seed protection, poisons, and fruit? Same theory.
A fruit is only plant flesh with water and citric acid and sugar in it.
Beetles and lizards also eat seeds and leaves. Even since the first mosses and ferns colonized the planet, the most abundant food was normally forest leaves. So plants "knew" they were being eaten since the times of the first animals because when you get eaten into oblivion, you dont know anything any more:(
All plants contain lots of sugar C6H12O6 in their sap, sugar is very easy thing for the plant to produce. Putting sugar into the seed pod is a easy for a plant as growing hairs from leaf cellulose, growing spines and making stings.
So, plants already had seedpod protection containing acids, poisons, soaps, wood protection like pine cones, and the only necessary change is to go from acid or cellulose, for example citric acid, to sugar, which is chemically an easy thing to do in evolution.
If a mutant tree one day makes a seed pod than some animals like so much, that they don't even break the seeds, then the tree's babies can travel many kilometers and be reborn into an animal nitrate dropping.
Fruit developed independently in yew trees, strawberries, figs, very simply by changing acid or poisonous seed pods into sugar ones that get transported for kilometers in every direction. If a fruit is not sugary, then it has some poisons like chilli peppers, spines like chestnuts, and other seed protection devices.