#AP Environmental Science: Primary Productivity - Your Ultimate Guide

Hey there, future AP Environmental Science superstar! Let's break down primary productivity. Think of this as your cheat sheet for acing the exam.

#Energy Flow in Ecosystems

#Gross Primary Productivity (GPP)

Key Concept

GPP is the total energy captured by producers (like plants) through photosynthesis. It's like a business's total revenue before expenses.

- Think of it as the **total solar energy** converted into chemical energy by plants. - It's the starting point of energy flow in an ecosystem.

#Respiration

Plants use some of the captured energy for their own needs through respiration.
This process releases energy, but some is lost as heat.
Think of it as the cost of doing business for plants.

#Net Primary Productivity (NPP)

Key Concept

NPP is the energy remaining after plants use some for respiration. It's the actual energy available for growth and to support other organisms.

- NPP = GPP - Respiration - Think of it as the business's profit after expenses. - It's the **real energy** available to the ecosystem.

#The Big Picture

Only about 1% of sunlight is captured by plants.

Quick Fact

Of that 1%, about 60% is lost to respiration, leaving only 0.4% of total solar energy as NPP.

- This small amount of energy drives the entire ecosystem.

#Why NPP Matters

NPP determines how much life an ecosystem can support.
Higher NPP usually means more biodiversity and more organisms at higher trophic levels.
Ecosystems with high NPP are generally more productive and stable.

#Visualizing Productivity

Net Primary Production

Caption: This image illustrates the concept of net primary production, showing how a small fraction of solar energy is converted into usable energy for ecosystems.

Memory Aid

GPP is like Gross Pay (total income), while NPP is like Net Pay (income after deductions). Remember, respiration is like the deductions (taxes) that reduce the total income.

Exam Tip

When you see questions about energy flow, remember that energy is lost at each step. Focus on the difference between GPP and NPP.

#Final Exam Focus

Key Concepts: GPP, Respiration, NPP, Energy Flow
Common Questions:
- Calculating NPP given GPP and respiration.
- Comparing the productivity of different ecosystems.
- Relating NPP to biodiversity and trophic levels.
Time Management: Quickly identify the type of question (calculation vs. conceptual) and allocate time accordingly.

Common Mistake

Don't confuse GPP and NPP. GPP is the total energy captured, while NPP is what's actually available to the ecosystem. Always remember respiration is the energy lost by plants.

#Practice Questions

Practice Question

Multiple Choice Questions

Which of the following best describes net primary productivity (NPP)? (A) The total amount of solar energy captured by producers. (B) The rate at which producers convert solar energy into chemical energy. (C) The amount of energy remaining after producers meet their own needs. (D) The total amount of energy available to all trophic levels.
If an ecosystem has a gross primary productivity (GPP) of 1000 kcal/m²/year and the producers’ respiration is 600 kcal/m²/year, what is the net primary productivity (NPP)? (A) 400 kcal/m²/year (B) 600 kcal/m²/year (C) 1000 kcal/m²/year (D) 1600 kcal/m²/year

Free Response Question

An ecosystem has a GPP of 2000 kcal/m²/year. The producers use 1200 kcal/m²/year for respiration.

(a) Calculate the NPP of this ecosystem. (1 point)

(b) Explain how NPP affects the biodiversity of an ecosystem. (2 points)

Answer Key:

Multiple Choice

Free Response

(a) NPP = GPP - Respiration = 2000 - 1200 = 800 kcal/m²/year (1 point)

(b) Higher NPP generally supports higher biodiversity because it provides more energy to support more organisms at various trophic levels. More energy means more available resources, allowing for more species to coexist. (2 points)

(c) Increased sunlight, higher temperatures, increased water availability or more nutrients could increase GPP. (2 points)

Remember, you've got this! Focus on understanding the core concepts, and you'll be well-prepared for the exam. Good luck!