Answer:
The last one and the first one.
hope I could help you pls give this answer a hart thx
Explanation:
secondary succesion takes place
Although nitrogen gas makes up 78% of the atmosphere, we can't use it because nitrogen atoms must be broken apart first before. This nitrogen is very much packed and bonded with its atoms and would be useless to use since it can't be used for plants.
Introduced species can harm our planet because in some regions of the world we are not prepared for their type of species, which can all in all cause damage.
Answer:
Humus
Explanation:
Also known as the uppermost layer of soil, that's for making soil more fertile due to its organic content.