1. When I hear the word 'pollution,' I think of the contamination of the environment by various harmful substances, such as air pollution from exhaust fumes or water pollution from industrial waste.

2. The main ecological problems include air pollution, water pollution, deforestation, habitat destruction, and climate change. These issues have significant impacts on the environment and biodiversity.

3. Greenpeace is an international environmental organization known for its activism in promoting environmental protection and conservation. They engage in campaigns and protests to raise awareness and address environmental issues like deforestation, pollution, and climate change.

4. The growth of cities often leads to urban sprawl, which can have negative effects on nature. It results in habitat loss for wildlife, increased pollution, and higher energy consumption. Proper urban planning and sustainable development are crucial to mitigate these impacts.

5. People can save natural resources by adopting sustainable practices such as reducing, reusing, and recycling materials, conserving water and energy, supporting clean energy sources, and advocating for responsible consumption and production. Individual actions, when combined, can make a significant difference in preserving our planet.