People and animals need to consume oxygen for breathing. Why can the volume fraction of oxygen in the air always maintain 21% 1. People and animals need to consume oxygen for breathing. Why can the volume fraction of oxygen in the air always maintain about 21%? 2. Can we draw a conclusion that nitrogen accounts for about 4 / 5 of the air from the burning experiment of red phosphorus in the bell jar? Why? 3. If there is water vapor in the air, will the content of water vapor change

People and animals need to consume oxygen for breathing. Why can the volume fraction of oxygen in the air always maintain 21% 1. People and animals need to consume oxygen for breathing. Why can the volume fraction of oxygen in the air always maintain about 21%? 2. Can we draw a conclusion that nitrogen accounts for about 4 / 5 of the air from the burning experiment of red phosphorus in the bell jar? Why? 3. If there is water vapor in the air, will the content of water vapor change

1. Although both human and animal respiration consume oxygen, some plants can produce oxygen through photosynthesis and so on. The whole world is in dynamic balance
2. No. besides nitrogen, there are other non combustion supporting gases in the air
3. The content of water vapor in the air is changeable, which is mainly related to the weather. Dew on the grass leaves in the morning is the condensation of water vapor

Animals can inhale oxygen and exhale carbon dioxide from the outside through breathing. Do plants also need to breathe?

Plants need to breathe, and plants not only need to breathe in leaves, but also in roots. There are stomata on the tender stems of plants, which also participate in respiration. Loose and breathable soil is conducive to the growth of plants, because roots also need to breathe. But indoor flowers will consume a lot of oxygen, and even make people in the room breathe

Plant respiration absorbs carbon dioxide and releases oxygen. Is that right

No. It should be that plants absorb carbon dioxide and release oxygen during photosynthesis. If plants breathe, it's the same as animals. They inhale oxygen and release carbon dioxide