The water cycle is a process that regulates the distribution of freshwater on Earth. It is a continuous supply of fresh water for ecosystems.

Fossil fuels are a non-renewable energy sources that are derived from the remains of ancient plants and animals.

Eclipses occur when the Sun, the Moon, or a planet moves into alignment. The most common types are solar and lunar eclipses.

Photosynthesis is a process that generates energy-rich molecules for plants and oxygen which is essential for the respiration on Earth.

All types of pollution result from different sources and have specific effects on the ecosystems. These types of pollution are interlinked.