Complete the sentences to describe the structure of DNA. The shape of the DNA molecule is called a double . The backbone of DNA is made of molecules and phosphate molecules. The "rungs" of DNA are made of .

There can be more freedom for them

Answergranite

They contributed many things, but here are some examples:

1) democracy - democracy as a political system was first implemented in ancient athens
2) some advances in mathematics - such as the pythagoras' law
3) the script - the roman script was adopted from ancient greek.

the correct answer is - c) the ecosystem would be unable to recover after any event.

if in a certain ecosystem, lot of new species of plants and animals are introduced, and those plants and animals can survive in those conditions, than the ecosystem will experience dramatic changes and would never be the same again.

the new species, which will practically be invasive species, will start to compete with the native ones, and very often the invasive species come as tougher. the ecosystem will start to rapidly change, the native species will have much more competition and their numbers will dwindle, and in no time the whole ecosystem will be unrecognizable.