AP Biology Questions on Food Webs and Energy Flow

📚 Quick Study Guide

• ☀️ Producers: Autotrophs that form the base of the food web, converting sunlight into chemical energy through photosynthesis (e.g., plants, algae).
• 🐛 Consumers: Heterotrophs that obtain energy by feeding on other organisms. Primary consumers eat producers, secondary consumers eat primary consumers, and so on.
• 🍄 Decomposers: Break down dead organic matter, releasing nutrients back into the ecosystem (e.g., bacteria, fungi).
• ⚡️ Trophic Levels: Each step in a food chain or food web. Energy transfer between trophic levels is inefficient.
• 🔢 Energy Transfer Efficiency: Typically around 10%, meaning only about 10% of the energy from one trophic level is transferred to the next. The rest is lost as heat or used for metabolic processes.
• ⚖️ Food Web vs. Food Chain: A food web is a more complex representation of the feeding relationships in an ecosystem, showing interconnected food chains.
• 📈 Energy Pyramids: Represent the flow of energy through trophic levels, with producers at the base and top predators at the apex. The size of each level reflects the amount of energy available.
• 🌍 Biomass: The total mass of organisms in a given area or volume. Biomass generally decreases as you move up trophic levels due to the loss of energy at each step.
• 🌡️ Thermodynamics: Laws of thermodynamics govern energy flow. The first law states that energy cannot be created or destroyed, only transformed. The second law states that energy transformations are not perfectly efficient, resulting in energy loss as heat.
• 🌿 Gross Primary Productivity (GPP): The total rate of photosynthesis in an ecosystem.
• 🪴 Net Primary Productivity (NPP): The rate of energy storage as biomass by plants or other primary producers and represents the energy available to consumers in the ecosystem. $NPP = GPP - Respiration$

🧪 Practice Quiz

1. Which of the following organisms is a primary producer?
   1. A) Grasshopper
   2. B) Fungus
   3. C) Algae
   4. D) Wolf
2. Approximately what percentage of energy is transferred from one trophic level to the next in an ecosystem?
   1. A) 90%
   2. B) 50%
   3. C) 10%
   4. D) 1%
3. Which of the following best describes a food web?
   1. A) A single sequence of organisms feeding on each other
   2. B) A complex network of interconnected food chains
   3. C) A linear pathway of energy flow
   4. D) A group of organisms that occupy the same trophic level
4. Decomposers play an important role in ecosystems by:
   1. A) Producing energy through photosynthesis
   2. B) Consuming primary producers
   3. C) Breaking down dead organic matter and releasing nutrients
   4. D) Converting sunlight into chemical energy
5. Which of the following is an example of a primary consumer?
   1. A) Snake
   2. B) Hawk
   3. C) Deer
   4. D) Mushroom
6. What does an energy pyramid represent?
   1. A) The flow of nutrients through an ecosystem
   2. B) The population size of different species
   3. C) The amount of biomass at different trophic levels
   4. D) The flow of energy through trophic levels
7. Which of the following equations describes Net Primary Productivity (NPP)?
   1. A) $NPP = Respiration - GPP$
   2. B) $NPP = GPP + Respiration$
   3. C) $NPP = GPP - Respiration$
   4. D) $NPP = GPP \times Respiration$