I don't think changing seasons can REMOVE CO2 from the air, but I do think instead it could add it to the air. It's a long process that involves several ecosystems and stuff. But, as the climate is getting warmer, ice caps are melting and within these ice caps... there are trapped bubbles of CO2 that are released ( I am not sure if this adds a lot of CO2 to the atmosphere, but I am sure that it does contribute to CO2 concentration).
In relation to your last statement... plant growth would actually reduce CO2 in the air because of the process of photosynthesis. Plants take in CO2 and give out O2 for us to breathe. In turn we conduct cellular respiration in which we take in the O2 and give out the CO2. So, plants are actually one good solution for decreasing CO2 levels.
The best answer would be the butterfly. Many insects go through different physical changes during growth. These insects include the butterfly. From being an egg it turned into a larva and grown into a caterpillar which later on become a butterfly.
