Introduction

To begin our discussion of energy flow in ecosystems, let's move from the Arctic to a much warmer place: a North American desert. Deserts contain diverse assemblages of plants, animals, and microorganisms.

This diversity is reflected in the variation in the sizes, shapes, and physiology of the animals making up the desert fauna, from termites in the soil to grasshoppers in the plant canopy to hawks in the sky. What links these animals together in the context of ecological functioning isn't necessarily their physical appearances or their evolutionary relationships. Rather, their ecological roles are determined by what they eat and by what eats them—that is, by their feeding, or trophic, interactions. In other words, the influence an organism has on the movement of energy and nutrients through an ecosystem is determined by the type of food it consumes as well as by what consumes it. For example, grasshoppers and scorpions are both arthropods, with similar morphology and physiology, yet their ecological effects on energy flow through the desert ecosystem are quite different. In the context of energy flow, grasshoppers are more similar to mule deer than to scorpions. Grasshoppers and mule deer are both generalist herbivores that consume a variety of desert plant species. The scorpion, by contrast, is a carnivorous arthropod feeding primarily on insects and thus has an ecological role more similar to that of a kestrel than to that of a grasshopper.

In this chapter, we continue the discussion of energy that we began in Chapter 20, describing its flow through ecosystems and the factors that control its movement through different trophic levels. We will also look at the feeding relationships in an ecosystem as an intricate web of interactions among species, a view that has important implications for energy flow and ecosystem function as well as for species interactions and community dynamics (topics that were covered in Units 4 and 5).

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Source: Bowman W., Hacker S.. Ecology. 6th ed. — Oxford University Press,2023. — 744 p.. 2023

Introduction

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