TOEFL Speaking Task 3

The concept of 'niche construction' refers to the process by which organisms actively modify their environment, thereby altering the selective pressures they and other species face. Unlike the traditional view where organisms passively adapt to fixed environments, niche construction highlights that organisms are agents in their own evolution. For instance, beavers building dams create aquatic habitats that change water flow and species composition, which in turn affects the beavers' survival and reproduction. This feedback loop between organism and environment is central to the concept.

Professor: Today, let's look at a real example. Consider the case of earthworms in temperate forests. Earthworms consume leaf litter and excrete nutrient-rich casts, which increases soil fertility. This change in soil composition allows different plants, like nitrogen-loving species, to thrive. As these plants grow, they provide more food for the earthworms and also alter the soil's moisture and structure. Over time, the forest floor becomes dominated by these new plants, which in turn supports a higher earthworm population. So, you see, the earthworms didn't just adapt to the forest; they actively transformed it, and that transformation shaped their own future survival and the entire ecosystem. This is exactly what niche construction is about.