#AP Environmental Science: Energy & Ecosystems 🌿

Hey there, future AP Environmental Science superstar! Let's get you prepped and confident for tomorrow's exam. We're going to break down energy transfers and ecosystem dynamics, making sure everything clicks into place. Think of this as your ultimate cheat sheet, designed to make complex ideas feel easy and intuitive. Let's do this!

#Energy Flow in Ecosystems

#Food Chains vs. Food Webs

• Food Chain: A linear path of energy transfer. Think of it like a single line of dominoes falling:
  • Producers (like plants) make their own food via photosynthesis.
  • Primary Consumers (herbivores) eat producers.
  • Secondary Consumers (carnivores) eat herbivores.
  • And so on...
• Food Web: A complex network of interconnected food chains. It's a more realistic model because organisms often have multiple food sources and predators. *

* They illustrate the complexity of real-world ecosystems.

*Caption: A food web from Lake Ontario, showing producers (green), primary consumers (orange), secondary consumers (blue), and tertiary consumers (purple).*

#Trophic Cascades 🌊

• A trophic cascade is a ripple effect in an ecosystem, often triggered by a change at the top of the food web.
  • Example: Increased sea otters → decreased sea urchins → increased kelp.

Practice Question

Multiple Choice:

1. Which of the following best describes a food web? (A) A linear sequence of energy transfer (B) A complex network of interconnected food chains (C) A single path of energy flow from producers to consumers (D) A diagram showing only predator-prey relationships

2. A trophic cascade is most directly initiated by changes in the population of: (A) Primary producers (B) Primary consumers (C) Apex predators (D) Decomposers

Free Response Question: Explain how a trophic cascade can lead to both positive and negative impacts on an ecosystem. Use a specific example to illustrate your explanation.

• Scoring Rubric:
  • (1 point) Correctly defining a trophic cascade.
  • (1 point) Explaining how a change in a top predator can cause a cascade.
  • (1 point) Providing a specific example of a trophic cascade (e.g., sea otters and kelp forests).
  • (1 point) Describing a positive effect of the cascade.
  • (1 point) Describing a negative effect of the cascade.

#Response to Disturbance: Feedback Loops

#Negative Feedback Loops 🔄

• Negative feedback loops help maintain stability. They counteract change, bringing a system back to its original state.
  • Think of it like a thermostat: if it gets too hot, the AC kicks on; if it gets too cold, the heat turns on.

* Example: * More herbivores → less vegetation → fewer herbivores (the system self-corrects).

*Caption: An example of a negative feedback loop involving a deer population and vegetation.*

#Positive Feedback Loops 📈

• Positive feedback loops amplify change, leading to instability. They push a system further away from its original state.
  • Think of it like a snowball rolling downhill: it gets bigger and faster as it goes.

* Example: * Melting ice → darker ground → more heat absorption → more melting. * Invasive species introduction → decline of native species → further ecosystem imbalance.

*Caption: The brown tree snake's introduction to Guam led to a positive feedback loop, decimating native bird populations.*

#Invasive Species and Feedback Loops

• Invasive species often create positive feedback loops.
  • They lack natural predators, so their populations explode.
  • This can lead to the decline or extinction of native species.

Practice Question

Multiple Choice:

1. Which of the following is an example of a negative feedback loop? (A) Melting ice caps leading to increased heat absorption (B) Increased herbivore population leading to decreased vegetation (C) Introduction of an invasive species leading to the decline of native species (D) Increased greenhouse gas emissions leading to increased global temperatures

2. A positive feedback loop is characterized by: (A) Counteracting changes to maintain stability (B) Amplifying changes, leading to instability (C) Returning a system to its original state (D) Reducing the rate of change in a system

Free Response Question: Describe how the introduction of an invasive species can lead to a positive feedback loop within an ecosystem. Use a specific example, such as the brown tree snake on Guam, to illustrate your answer.

• Scoring Rubric:
  • (1 point) Correctly defining a positive feedback loop.
  • (1 point) Explaining how the introduction of an invasive species can initiate a positive feedback loop.
  • (1 point) Providing a specific example of an invasive species (e.g., brown tree snake).
  • (1 point) Describing how the invasive species amplifies the original change.
  • (1 point) Explaining the consequences of this positive feedback loop on the ecosystem.

#Final Exam Focus 🎯

• High-Priority Topics:
  • Food webs and trophic levels
  • Trophic cascades
  • Negative and positive feedback loops
  • Impacts of invasive species
• Common Question Types:
  • Multiple-choice questions testing definitions and examples.
  • Free-response questions requiring you to explain concepts and apply them to real-world scenarios.
  • Questions that combine multiple units (e.g., linking feedback loops to climate change or biodiversity loss).
• Last-Minute Tips:
  • Time Management: Don't get bogged down on a single question. Move on and come back if you have time.
  • Common Pitfalls: Misidentifying positive and negative feedback loops. Not understanding the connections between different parts of an ecosystem.
  • Strategies: Read each question carefully. Underline keywords. Use diagrams and examples to support your answers.

You're all set! Go ace that exam! 🚀