Water in Ecosystems — Reading Comprehension

Water moves continuously through Earth's ecosystems, linking living organisms with the air, land, and oceans. The water cycle describes this constant movement, shaping the environment and supporting life. Understanding how water travels through different reservoirs and processes helps scientists predict weather, manage resources, and protect habitats. Water is not only essential for survival; it is the foundation for all biochemical reactions in living things.

The Mechanisms of the Water Cycle

The water cycle is driven by energy from the sun, causing water to change states and move between locations. In evaporation, liquid water from oceans, lakes, and rivers changes into water vapor, a gas, as it absorbs heat. Plants also release water vapor through transpiration. Together, these processes contribute about 90% of the moisture in the atmosphere. As the air cools, water vapor turns back into liquid droplets in a process called condensation, forming clouds. When droplets combine and grow heavy, they fall to Earth as precipitation—rain, snow, sleet, or hail. Some water runs off the land into rivers and lakes, while some seeps into the ground through infiltration, replenishing groundwater supplies.

Reservoirs, Interactions, and Importance

Most of Earth's water—about 97%—is stored in the oceans, the largest reservoir. Freshwater is found in ice caps and glaciers (about 2%), as well as in groundwater, lakes, rivers, and the atmosphere. Water moves between these reservoirs at different rates. For example, a water molecule may stay in the ocean for thousands of years but only spend days in the atmosphere. Water is a universal solvent, dissolving many substances and enabling essential chemical reactions in all living things. Every organism depends on water to transport nutrients, remove waste, and regulate temperature.

Human Impacts and Broader Implications

Humans have a significant influence on the water cycle. Dams and irrigation systems change the natural flow of rivers, affecting habitats and groundwater levels. Pollution can contaminate freshwater sources, making them unsafe for wildlife and people. Climate change is altering rainfall patterns and increasing evaporation rates, which can lead to droughts or floods in different regions. Scientists use data from satellites, weather stations, and field studies to monitor these changes and develop strategies for sustainable water management. Understanding the water cycle helps us protect resources and respond to environmental challenges.

Water's movement through ecosystems highlights the interconnectedness of Earth's systems. Recognizing how water supports life and how our actions affect its movement is vital for a sustainable future.

Interesting Fact:
At any moment, only about 0.001% of Earth's water is found in the atmosphere as vapor, but this small amount is crucial for weather and climate!

What is the main purpose of the water cycle in ecosystems?

Which process describes water vapor turning back into liquid droplets in the atmosphere?

Where is most of Earth's water stored?

What is the primary source of energy that drives the water cycle?

What does infiltration mean in the context of the water cycle?

Based on the passage, what is a solvent?

Why is water important for all living organisms?

How can humans affect the natural water cycle? (Choose the BEST answer)

True or False: Only about 2% of Earth's water is found in ice caps and glaciers.

True or False: Water in the atmosphere is not important for weather.