tailieunhanh - Insect Ecology - An Ecosystem Approach 2nd ed - Chapter 2

SECTION I ECOLOGY OF INDIVIDUAL INSECTS THE INDIVIDUAL ORGANISM IS A FUNDAMENTAL unit of ecology. Organisms interact with their environment and affect ecosystem processes largely through their cumulative physiological and behavioral responses to environmental variation. Individual success in finding and using necessary habitats and resources to gain reproductive advantage determines fitness. | SECTION I ECOLOGY OF INDIVIDUAL INSECTS THE INDIVIDUAL ORGANISM IS A FUNDAMENTAL unit of ecology. Organisms interact with their ----- environment and affect ecosystem processes largely I through their cumulative physiological and behavioral responses to environmental variation. Individual success in finding and using necessary habitats and resources to gain reproductive advantage determines fitness. Insects have a number of general attributes that have contributed to their ecological success Romoser and Stoffolano 1998 . First small size an attribute shared with other invertebrates and microorganisms has permitted exploitation of habitat and food resources at a microscopic scale. Insects can take shelter from adverse conditions in microsites too small for larger organisms . within individual leaves . Large numbers of insects can exploit the resources represented by a single leaf often by partitioning leaf resources. Some species feed on cell contents others on sap in leaf veins some on top of the leaf others on the underside and some internally. At the same time small size makes insects sensitive to changes in temperature moisture air or water chemistry and other factors. Second the exoskeleton shared with other arthropods provides protection against predation and desiccation or water-logging necessary for small organisms and innumerable points of muscle attachment for flexibility . However the exoskeleton also limits the size attainable by arthropods. The increased weight of exoskeleton required to support larger body size would limit mobility. Larger arthropods occurred prehistorically before the appearance of faster more flexible vertebrate predators. Larger arthropods also occur in aquatic environments where water helps support their weight. Third metamorphosis is necessary for exoskeleton-limited growth but permits partitioning of habitats and resources among life stages. Immature and adult insects can differ dramatically in form and function and thereby .