TOEFL Complete the Words: Ecology (Intermediate)
Ecology in TOEFL
Ecology is a field that examines how living organisms interact with one another and with their environment. In simple terms, this topic focuses on the relationships among plants, animals, and other forms of life within an ecosystem. In TOEFL passages on this subject, you may encounter terms related to food chains, population changes, habitat conditions, and the roles played by different species.
Practice Questions
Question 1
After a volcanic eru_ _ _ _ _ or forest fire, the land may appear almost lifeless at first. Yet bare ground rar_ _ _ remains empty for long. Mosses, grasses, and other hardy species often arrive before larger plants can sur_ _ _ _, gradually altering the soil and local conditions. As these early organisms spread, they make the environment more sui_ _ _ _ _ for shrubs and trees. This gradual replacement of one biological community by another is known as ecological succession. The process may take de_ _ _ _ _ or even centuries, depending o_ climate and soil con_ _ _ _ _ _ _. By tracing these long-term changes, ecologists can better understand how ecosystems recover from disturbance and how st_ _ _ _ communities are eventually established.
Explanation
Complete passage
After a volcanic eruption or forest fire, the land may appear almost lifeless at first. Yet bare ground rarely remains empty for long. Mosses, grasses, and other hardy species often arrive before larger plants can survive, gradually altering the soil and local conditions. As these early organisms spread, they make the environment more suitable for shrubs and trees. This gradual replacement of one biological community by another is known as ecological succession. The process may take decades or even centuries, depending on climate and soil conditions. By tracing these long-term changes, ecologists can better understand how ecosystems recover from disturbance and how stable communities are eventually established.
Ecological succession refers to the gradual process by which the composition of an ecosystem changes over time. It often begins after a major disturbance, such as a volcanic eruption, wildfire, or flood, when the original community has been damaged or removed. New organisms begin to colonize the area, and their presence slowly changes the environment.
The first species to appear are usually hardy organisms that can survive under difficult conditions. These early species may improve the soil, add organic material, or create shade, making it easier for other plants to grow later. As conditions change, one community is replaced by another, and the ecosystem becomes more complex.
Ecologists study succession because it helps explain how natural communities recover and develop. It also shows that ecosystems are not fixed. Instead, they are shaped by long-term interactions among organisms, climate, and environmental change.
Question 2
A forest does not change only when trees are cut d_ _ _ completely. Even a narrow road or a small cleared area can al_ _ _ conditions along the bou_ _ _ _ _ between woodland a_ _ open land. Sunlight becomes more int_ _ _ _, wind reaches farther into the habitat, and moisture levels often drop. Species that depend _ _ cool, shaded conditions may struggle to survive near this edge. For ecologists, these boundary-related ch_ _ _ _ _ are known as edge effects. Their influence can extend well be_ _ _ _ the visible border itself, affecting nesting patterns, plant growth, and predator activity. A hab_ _ _ _ may therefore appear large on a map while offering far less suitable interior space than its total area would suggest.
Explanation
Complete passage
A forest does not change only when trees are cut down completely. Even a narrow road or a small cleared area can alter conditions along the boundary between woodland and open land. Sunlight becomes more intense, wind reaches farther into the habitat, and moisture levels often drop. Species that depend on cool, shaded conditions may struggle to survive near this edge. For ecologists, these boundary-related changes are known as edge effects. Their influence can extend well beyond the visible border itself, affecting nesting patterns, plant growth, and predator activity. A habitat may therefore appear large on a map while offering far less suitable interior space than its total area would suggest.
Edge effects refer to the environmental changes that occur at the boundary between two different habitats, such as a forest and a grassland. Conditions near the edge are often different from those found deeper inside the habitat. Light, temperature, wind, and humidity can all shift noticeably in these transition zones.
These changes matter because many species are adapted to a particular set of conditions. Some animals and plants thrive near edges, while others depend on the more stable environment of the habitat interior. As a result, the creation of new edges can change which species are able to live in an area.
Ecologists study edge effects to understand how habitat fragmentation influences ecosystems. Even when a habitat still exists, dividing it into smaller sections can reduce the amount of protected interior space. This makes edge effects an important concept in conservation biology and land-use planning.
Question 3
A lake can appear hea_ _ _ _ for years and then change surprisingly fast after the arrival o_ a new species. Fish that once rep_ _ _ _ _ _ _ in shallow water may decline, native plants may disappear, and food relationships can sh_ _ _ in unexpected ways. In many cases, the turning po_ _ _ is not pollution or climate, but the spread of an org_ _ _ _ _ that did not originally be_ _ _ _ there. Such species are often int_ _ _ _ _ _ _ through shipping, trade, or human travel. Once established, they may reproduce quickly and face few natural en_ _ _ _ _ in the new environment. Because of this, they can out_ _ _ _ _ _ _ native species for food or space and alter the balance of the ecosystem. Ecologists refer to this process as biological invasion.
Explanation
Complete passage
A lake can appear healthy for years and then change surprisingly fast after the arrival of a new species. Fish that once reproduced in shallow water may decline, native plants may disappear, and food relationships can shift in unexpected ways. In many cases, the turning point is not pollution or climate, but the spread of an organism that did not originally belong there. Such species are often introduced through shipping, trade, or human travel. Once established, they may reproduce quickly and face few natural enemies in the new environment. Because of this, they can outcompete native species for food or space and alter the balance of the ecosystem. Ecologists refer to this process as biological invasion.
A lake can appear hea _ _ _ _ for years and then change surprisingly fast after the arrival o _ a new species. Fish that once rep _ _ _ _ _ _ _ in shallow water may decline, native plants may disappear, and food relationships can sh _ _ _ in unexpected ways. In many cases, the turning po _ _ _ is not pollution or climate, but the spread of an org _ _ _ _ _ that did not originally be _ _ _ _ there. Such species are often int _ _ _ _ _ _ _ through shipping, trade, or human travel. Once established, they may reproduce quickly and face few natural en _ _ _ _ _ in the new environment. Because of this, they can out _ _ _ _ _ _ _ native species for food or space and alter the balance of the ecosystem. Ecologists refer to this process as biological invasion.
