WHY DOES THE WORLD STAY GREEN? Nutrition and survival of plant-eaters doc

[...]... in the maturing flowers and when the grubs hatch they survive only if they can eat the developing seed in the newly developing fruit The large 20 Why does the world stay green? tunnel in the flesh of the apple that so mars the fruit is made by the mature caterpillar eating its way out of the fruit to pupate The females of many bugs that suck the contents out of seeds cannot mature their eggs if they... protein These amino acids are so dilute in plants for most of the time that herbivores are constantly striving to get enough of them As a result they can produce few viable young, 8 Why does the world stay green? and most of those they do produce soon starve And they will die whether or not others of their own – or any other – kind are trying to eat the same food I have referred several times to the commonly... programmed by the plant’s genes; they grow into the gall within which the insect lives But creating somewhere to live is not the point of the exercise If the insect within is a 22 Why does the world stay green? chewer it grazes the cells lining the cavity of the gall so that they continue to proliferate If it is a sap-sucker it feeds on the contents of these lining cells In either case the plant is... by The supply of the four basic chemicals, on the other hand, is not unlimited However, carbon, hydrogen and oxygen are all very abundant and readily available There seems little prospect they could run out Nitrogen is equally abundant – but 99.95 per cent of it is inert gas in the atmosphere, and so 10 Why does the world stay green? unavailable to plants and animals The remaining 0.05 per cent of the. .. behaviour by these birds, although not often noted I have watched white cockatoos attacking a large field of daffodils, picking the flowers off, carefully opening them and eating 18 Why does the world stay green? just the tiny soft developing seeds within the ovary And each year I have to endure the same white cockatoos descending on my walnut tree, biting open the unripe green fruit and eating the soft immature... Why does the world stay green? Figure 1.1 Canadian balsam fir trees defoliated by spruce budworm caterpillars covered with the silken thread left by the caterpillars lowering themselves to the ground to pupate Photo courtesy of Canadian Forest Service the world s plant production So, as with the forests, most of the world remains green In the face of all this, some obvious questions remain: Why, then,... bore holes in the side of the fruit and then clean out the soft developing seeds within But remember the cockatoos in the farmer’s paddock first attacked the germinating barley seedlings I need to turn to a study of the ecology of a mammal to explain why they did this Feral house mice living in and around irrigated rice fields in NSW subsist for most of the year on the large amounts of ripe grain spilt... their nestlings Another Australian parrot, the galah, in the wheat belt of Western Australia does this, concentrating first on the new seeds of weeds growing around the crop, and then moving into the crop as the seed-heads begin to form and swell Further evidence of the predilection of Australian parrots for the unripe seed of introduced plants is common About the same time that the white cockatoos... remaining plants untouched and depart And they do not return to the paddock until the plants are fully grown, and the grain in the seed heads is starting to fill out Then they descend again, push plants over, and eat the newly forming ‘milk-ripe’ seeds in the heads But as soon as the crop is mature, and seed is set, they again depart, leaving the remaining plants untouched Why would they do this?’ he asked... aphids and mites Their bodies are so tiny that they will float away on the merest breeze Many have evolved the behaviour of climbing to the top of a plant and launching themselves from it early in the morning The air is warming and rising then, so they are quickly carried upwards and may travel great distances before falling from the sky late in the day as the air cools (Try sitting out in the garden . because they reduce the number of Why does the world stay green? 8 Why the world green-book.qxd 6/9/05 2:41 PM Page 8 herbivores by eating so many of them. Their. class="bi x0 y0 w0 h0" alt="" WHY DOES THE WORLD STAY GREEN? Nutrition and survival of plant-eaters TCR White Why the world green-book.qxd 12/9/05 12:07