If you have 25 g. of a sample that has undergone 4 Half-Lives, how much sample did you have at
the beginning?

#20 which type of bond is formed when bases pair in dna? ionic bond covalent bond coordinate bond hydrogen bond

2. what two items do autotrophs take from the environment to produce their food? 3. what are the two items that are released during transpiration from leaves? 4. what are the two membranes of the system? a.what are the two stages of photosynthesis? what are the two parts of photosynthesis?

Aecosystem is if it can continue to function over long periods of time