If intelligent extraterrestrials visited earth 475 million years ago, and then again 300 million years ago (at the close of the carboniferous period), what trends would they have noticed in earth's terrestrial vegetation over this period?

since there are no options posted i'll give you a few examples.

a dolphin's flipper, bird's wing, cat's leg.

the nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and dna, the building blocks of all life. plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter.

is it multiple choice?