1. Which organisms are capable of converting gaseous nitrogen in the air into a form that other living organisms can use? (1 point)
A.)nitrogen-fixing bacteria
B.)denitrifying bacteria
C.)decomposers
D.)producers
2. Which step in the nitrogen cycle is accelerated at the beginning of the eutrophication process? (1 point)
A.)denitrification
B.)nitrogen fixation
C.)producer uptake of nitrogen
D.)consumer decomposition
3. Which of the following is carried out by denitrifying bacteria? (1 point)
A.)break down large, nitrogen-rich molecules to simple molecules
B.)build large, nitrogen-rich molecules from simple molecules
C.)convert biologically useful nitrogen to gaseous nitrogen
D.)convert gaseous nitrogen to biologically useful nitrogen
4. Which type of organism moves nitrogen from cells of producers back to the soil? (1 point)
A.)decomposers
B.)consumers
C.)nitrogen-fixing bacteria
D.)denitrifying bacteria
5. What would be the consequence of an ecosystem that had no nitrogen-fixing bacteria? (1 point)
A.)Nitrogen from decomposing animals would never be returned to the soil.
B.)Decomposers would not be able to break down the nitrogen present in plants they feed on.
C.)Plants would have to rely on biologically available nitrogen present in the soil.
D.)Consumers would not survive since they would have no way to obtain the nitrogen they need.
My Answers:
A
D
C
A
C
1. To answer question 1, you need to understand which organisms are capable of converting gaseous nitrogen in the air into a form that other living organisms can use. Nitrogen fixation is the process of converting atmospheric nitrogen gas (N2) into biologically useful forms of nitrogen, such as ammonia (NH3) or nitrate (NO3-). Nitrogen-fixing bacteria are the organisms that carry out this process. They have the enzyme nitrogenase, which can break the triple bond of N2 and convert it into a form that can be utilized by other organisms. Option A, nitrogen-fixing bacteria, is the correct answer.
2. To answer question 2, you need to understand which step in the nitrogen cycle is accelerated at the beginning of the eutrophication process. Eutrophication is the process by which a body of water becomes enriched with nutrients, often due to excessive inputs of nitrogen and phosphorus from human activities. This excess nutrient input leads to an overgrowth of algae, which disrupts the ecosystem balance. In this context, the acceleration at the beginning of the eutrophication process refers to the increase in nutrient availability, particularly nitrogen. The step that is specifically accelerated is nitrogen fixation (option B), as it leads to an increase in the availability of biologically useful forms of nitrogen in the water.
3. To answer question 3, you need to understand what denitrifying bacteria do. Denitrifying bacteria are organisms that carry out denitrification, which is the process of converting nitrate (NO3-) back into atmospheric nitrogen gas (N2). This process occurs in anaerobic conditions, where oxygen is limited. Denitrifying bacteria use nitrate as an electron acceptor and convert it into nitrogen gas, releasing it back into the atmosphere. Option C, convert biologically useful nitrogen to gaseous nitrogen, is the correct answer.
4. To answer question 4, you need to understand which type of organism moves nitrogen from cells of producers back to the soil. Producers, such as plants, take up nitrogen from the soil and incorporate it into their tissues. When these producers die or are consumed, the nitrogen present in their cells needs to be recycled back into the soil for reuse. Decomposers, which include bacteria and fungi, play an essential role in breaking down organic matter and returning nutrients to the soil. Therefore, option A, decomposers, is the correct answer.
5. To answer question 5, you need to understand the consequence of an ecosystem without nitrogen-fixing bacteria. Nitrogen-fixing bacteria are the primary organisms responsible for converting atmospheric nitrogen into biologically usable forms, such as ammonia or nitrate. Without these bacteria, plants would have to rely solely on the nitrogen present in the soil, which may become depleted over time. This would result in limited nitrogen availability for plant growth, making it difficult for plants to survive and reproduce. Therefore, option C, plants would have to rely on biologically available nitrogen present in the soil, is the correct answer.