The use of civil service exams
The correct answer to this open question is the following.
You did not provide any excerpt, text, reference, or context to answer this question. That makes it difficult to exactly what you are referring to.
However, trying to help you and doing some research we can say the following.
One historical event or development in the period 1830 to 1860 that is not explicitly mentioned that could be used to support Hahn’s interpretation is how the United States became the engine of the ecom¿nomy of the planet because of its industrial capacity. How the Gross Domestic Product grew and the many opportunities the US offered to immigrants to work in major industries such as the Standard Oil Company of John F. Rockefeller, or the Steel company of Andrew Carnegie.
Innovations and the use of technology helped industries to earn more profits and invest that money in the creation of jobs and the spread of their operations nationwide.
Federalism is the division of power between states and the federal government.
Federal law preempts state law. This is due to the National Supremacy Clause in Article 6 of the U.S. Constitution.
Answer:
reflect the conditions and changes of an environment where they live.
Explanation:
Effective indicator species need distinct environmental factors to sustain and survive in the environment. They reflect the conditions and changes of an environment where they live.
Fishes, specifically steelhead trouts, are an effective indicator species because steelhead trouts require distinct environmental conditions to survive such as temperature of the water, availability of food, specific waterbed, etc. If there is an absence of steelhead trouts in a particular body of water, scientists can easily determine that the water has environmental problems.
