It's called radioactive dating
Answer: Availability of water
Explanation:
When a person is travelling from a forest ecosystem towards grassland ecosystem the number of trees gets reduced in number.
The trees are replaced by prairie grasses. This change is because of less water availability in the area having grass.
The amount of precipitation decides the type of vegetation found in that area.So the area having trees would be having more precipitation as compared to the area having prairie grass.
The answer would be, record data . This step is crucial to an experiment because you would be able to see the results.
