#Biodiversity: Your Night-Before-the-Exam Guide 🌍

Hey there, future AP Environmental Science ace! Let's dive into biodiversity, a crucial topic that pops up everywhere on the exam. Think of this as your ultimate cheat sheet, designed to make everything click right before the big day.

#What is Biodiversity?

Biodiversity is all about the variety of life on Earth – plants, animals, and everything in between. It's not just about how many different species there are, but also how different they are from each other.

#Forms of Biodiversity

There are three main types of biodiversity, and each plays a vital role in keeping our planet healthy.

#Genetic Diversity 🧬

Genetic diversity is super important! It's the variety of genes within a single species.

• Why it matters: Think of it like a team with lots of different skills. The more genetic diversity, the better a species can adapt to changes, like new diseases or climate shifts.
• Example: Imagine a population of frogs. If some frogs have genes that make them resistant to a certain fungus, they'll survive an outbreak, while others might not.
• Population Bottleneck: This is when a population shrinks dramatically, losing a lot of its genetic diversity. It's like going from a full deck of cards to just a few.
  • Causes: Natural disasters, human activities, diseases.
  • Impact: Makes the population more vulnerable to extinction.

#Species Diversity 🐅

Species diversity is about the variety of different species in an ecosystem.

• Why it matters: Different species have different jobs in an ecosystem. The more species, the more stable and resilient the ecosystem is.
• Example: A forest with lots of different trees, insects, and birds is more likely to survive a disturbance than a forest with just one type of tree.
• Low Diversity Impact: If one species is wiped out in a low-diversity ecosystem, there may not be another to take its place, leading to collapse.

#Habitat Diversity ⛰️

Habitat diversity is the variety of different habitats in a given area.

• Why it matters: Different habitats support different species. More habitat diversity means more overall biodiversity.
• Example: A region with forests, grasslands, and wetlands will support more species than a region with just one type of habitat.
• Loss of Habitat: Leads to loss of specialist species and reduced numbers of species with large territorial needs.

#Richness vs. Evenness

These are two ways to measure biodiversity:

#Richness

• Definition: How many different species are present in an ecosystem.

• Trend: Generally decreases as you move away from the equator.

• Measurement: Simpson’s Diversity Index is a common way to measure richness (ranges from 0 to 1, with 1 being the highest richness).

  $$D = 1 - \frac{\sum n(n-1)}{N(N-1)}$$

  Where:

  • n = the total number of organisms of a particular species

  • N = the total number of organisms of all species

  

#Evenness

• Definition: How evenly distributed the populations of each species are.
• High Evenness: Relatively equal population sizes among species.
• Low Evenness: One or few species dominate the population.
• Ideal Ecosystem: High richness and high evenness.

#Ecosystem Resistance and Resilience

These terms describe how ecosystems respond to disturbances:

#Ecosystem Resistance

• Definition: How much an ecosystem is affected by a disturbance.
• High Resistance: The ecosystem is barely affected.
• Low Resistance: The ecosystem is severely impacted.

#Ecosystem Resilience

• Definition: How quickly an ecosystem recovers after a disturbance.
• High Resilience: The ecosystem bounces back quickly.
• Low Resilience: The ecosystem takes a long time to recover, or may not recover at all.

#Final Exam Focus

• High-Value Topics: Genetic diversity, species diversity, habitat diversity, ecosystem resistance, and resilience.
• Common Question Types:
  • Multiple choice: Identifying the different forms of biodiversity and their importance.
  • FRQs: Analyzing how changes in biodiversity affect ecosystem stability and function.
  • Math-based questions: Calculating Simpson’s Diversity Index and interpreting the results.
• Last-Minute Tips:
  • Review the definitions of key terms.
  • Think about real-world examples of biodiversity loss and its impacts.
  • Practice calculating Simpson’s Diversity Index.
  • Stay calm and confident – you’ve got this!

#Practice Questions

Practice Question

#Multiple Choice Questions

1. Which of the following best describes genetic diversity? (a) The variety of ecosystems in a region. (b) The number of different species in an area. (c) The variety of genes within a species. (d) The range of habitats available in an area.
2. A population bottleneck is most likely to result in: (a) An increase in genetic diversity. (b) A decrease in genetic diversity. (c) No change in genetic diversity. (d) An increase in species diversity.
3. An ecosystem with high resilience is best described as: (a) An ecosystem that is not affected by disturbances. (b) An ecosystem that recovers quickly after a disturbance. (c) An ecosystem with low species diversity. (d) An ecosystem with high species richness but low evenness.

#Free Response Question (FRQ)

A large area of forest is cleared for agriculture. Discuss the impacts of this action on biodiversity, including genetic diversity, species diversity, and habitat diversity. Explain how the loss of biodiversity can affect the ecosystem's resistance and resilience.

#Scoring Breakdown

• Genetic Diversity (2 points):
  • 1 point for explaining that clearing the forest reduces the population size, leading to a loss of genetic diversity.
  • 1 point for explaining that the reduced genetic diversity makes the remaining population more vulnerable to disease and environmental changes.
• Species Diversity (2 points):
  • 1 point for explaining that clearing the forest reduces the number of species in the area.
  • 1 point for explaining that the loss of species diversity can disrupt food webs and other ecosystem processes.
• Habitat Diversity (2 points):
  • 1 point for explaining that clearing the forest reduces the number and variety of habitats.
  • 1 point for explaining that the loss of habitat diversity can lead to the loss of species that depend on those habitats.
• Ecosystem Resistance and Resilience (2 points):
  • 1 point for explaining that the loss of biodiversity reduces the ecosystem's resistance to disturbances.
  • 1 point for explaining that the loss of biodiversity reduces the ecosystem's resilience, making it slower to recover from disturbances.