Ecosystems Mixed Practice
| # | Answer |
|---|---|
| 1 | An ecosystem is a community of living organisms interacting with each other and with the nonliving chemical environment, including air, water, soil, and dissolved substances. |
| 2 | Examples include pH and dissolved oxygen. pH affects chemical reactions and organism survival, while dissolved oxygen determines whether aquatic organisms can perform aerobic respiration. |
| 3 | Carbon dioxide is a reactant used by producers in photosynthesis to build glucose and other organic molecules, moving carbon from the atmosphere into the food web. |
| 4 | The Sun is the main energy source. Producers capture sunlight through photosynthesis and convert it into chemical energy stored in organic molecules, which then enters the food chain. |
| 5 | Water dissolves many ions and molecules, allowing transport, chemical reactions, nutrient availability, and waste removal in organisms and ecosystems. |
| 6 | 6CO2 + 6H2O + light energy -> C6H12O6 + 6O2 |
| 7 | C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy |
| 8 | Photosynthesis stores energy by making glucose and oxygen, while respiration releases energy by breaking down glucose using oxygen. The products of one process are the reactants of the other, helping cycle carbon and oxygen. |
| 9 | A nutrient cycle is the movement of a chemical element through living organisms and the nonliving environment. One example is the carbon cycle. |
| 10 | Light intensity can change the rate of photosynthesis. As light increases, the rate usually rises until another factor becomes limiting. |
| 11 | Aquatic organisms may experience stress or die because aerobic respiration becomes difficult when oxygen is limited. |
| 12 | From the equation, 1 mol glucose reacts with 6 mol O2. Therefore, 2 mol glucose need 12 mol O2. |
| 13 | Using 6CO2 -> 1 glucose, 18 mol CO2 can produce 3 mol glucose. |
| 14 | Decomposers break down dead organic matter and release nutrients such as nitrogen, phosphorus, and carbon compounds back into the environment for reuse by other organisms. |
| 15 | Nitrogen gas is converted into usable forms like ammonia, nitrite, and nitrate by nitrogen-fixing bacteria and other microbes. Plants absorb nitrate or ammonium from soil. |
| 16 | Eutrophication is nutrient enrichment of water that causes excessive algal growth. It is often triggered by high nitrate or phosphate runoff from fertilizers or waste. |
| 17 | When algae die, decomposer bacteria break them down and use dissolved oxygen during respiration, which can lower oxygen levels and create hypoxic conditions. |
| 18 | It is acidic because any pH below 7 is acidic. |
| 19 | Low pH can change nutrient solubility and increase the availability of some toxic metals while reducing access to essential nutrients such as calcium, magnesium, and phosphorus. |
| 20 | Matter cycles through ecosystems in forms such as carbon, nitrogen, and water, while energy flows one-way from the Sun through organisms and is lost as heat at each transfer. |
| 21 | Consumers may have less chemical energy available because less glucose and biomass are produced, leading to reduced growth, reproduction, and survival. |
| 22 | Persistent pollutants are not easily broken down and can build up in organisms. Their concentration increases at higher trophic levels, making top predators especially vulnerable. |
| 23 | The pesticide contains carbon, hydrogen, chlorine, nitrogen, and oxygen atoms in the ratio shown by the subscripts. |
| 24 | Primary consumers receive 100 kJ. Secondary consumers receive 10 kJ. |
| 25 | Example: Fertilizer runoff adds nitrates and phosphates to water, causing algal blooms. Decomposition then reduces dissolved oxygen, harming fish and other aquatic life. The altered chemistry can also reduce water quality and shift the balance of the ecosystem. |