Sunday, March 04, 2007

Life on Earth - Episode 04 - The Swarming Hordes

"This fourth episode details the relationship between flowers and insects. There are some one million classified species of insect, and two or three times as many that are yet to be labeled. Around 300 million years ago, plants began to enlist insects to help with their reproduction, and they did so with flowers. Although the magnolia, for instance, contains male and female cells, pollination from another plant is preferable as it ensures greater variation and thus evolution. Flowers advertise themselves by either scent or display. Some evolved to produce sweet-smelling nectar and in turn, several insects developed their mouth parts into feeding tubes in order to reach it. However, to ensure that pollination occurs, some species — such as the orchid — have highly complicated mechanisms that must be negotiated first. Others, such as the yucca and its visiting moths, are dependent on one another. Hunters, such as the mantis, are camouflaged to match the flowers and leaves visited by their prey. Since an insect’s skin is chitinous, it has to shed it periodically in order to grow, and the caterpillar, its chrysalis or cocoon and resulting butterfly or moth is one of the more complex examples. Termites, ants and some bees and wasps overcame any limitations of size by grouping together and forming superorganisms. The green tree ants of south-east Asia are shown to display the most extraordinary co-operation when building their nests."

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