Answer:
Weather conditions
Explanation:
Food can be limited based on location, however, scientists can control what kind of food it is. Soil can be tested and experimented on. There can be a lot of it and different kinds. Space is fought over because of territories and is limited compared to how many people and animals there are. Weather is not something that can be controlled in an experiment since it is sporadic.
Recombinant DNA techniques, for example, increase milk productions in cows. Another example would be, transgenic salmon grow faster than wild salmon.
In plants it's identical.. ND in animals it's genetically unique
The answers are water and carbon dioxide.
