#AP Environmental Science: Island Biogeography & Invasives - Your Last-Minute Guide 🚀

Hey there, future AP Environmental Science superstar! Let's get you feeling confident and ready to ace this exam. We're diving into Island Biogeography and Invasives, two topics that often pop up and can be real game-changers if you know them well. Let's break it down!

#Island Biogeography Theory: The Basics 🏝️

#What's the Big Idea?

Island Biogeography Theory (IBT) explains how the size and location of an island affect the number of species that live there. It's all about the balance between immigration (new species arriving) and extinction (species dying out). Think of it like a bustling city: people move in, and people move out, and there's a sweet spot where things are stable.

#Immigration vs. Extinction

• Immigration: New species arrive on the island.
• Extinction: Species already on the island die out.

Initially, immigration rates are high because there are open niches. As more species arrive, competition increases, and extinction rates rise. Eventually, these two forces reach an equilibrium, determining the island's species richness.

#The Role of Island Size and Distance

Island size and distance from the mainland are HUGE factors in determining species richness.

• Larger Islands:
  • Have more habitats and resources.
  • Support larger populations, which are less prone to extinction.
  • Higher immigration rates because they are easier to spot.
• Islands Closer to the Mainland:
  • Easier for species to reach, leading to higher immigration rates.

#Visualizing the Theory

• This graph shows how immigration and extinction rates change over time. The point where the lines cross is the equilibrium point.

• This graph illustrates how island size and distance affect the equilibrium number of species. Larger, closer islands have higher species richness.

#Invasive Species: The Disruptors ⚠️

#Endemic vs. Invasive Species

• Endemic Species:
  • Native to a specific area.
  • Often specialists with narrow ecological niches.
  • Vulnerable to environmental changes and competition.
• Invasive Species:
  • Non-native species that spread rapidly and cause harm.
  • Often generalists with broad ecological niches.
  • Outcompete endemic species for resources.

#Why Are Invasives So Successful?

• Lack of Natural Predators: Invasive species often arrive without their natural enemies, allowing their populations to explode.
• Generalist Nature: They can thrive in a variety of conditions and exploit many different resources.
• Rapid Reproduction: Many invasive species reproduce quickly, allowing them to spread rapidly.

#The Impact of Invasives

• Displacement of Endemics: Invasive species can outcompete and drive endemic species to extinction.
• Habitat Alteration: They can change the structure and function of ecosystems.
• Economic Costs: Invasives can cause significant economic damage to agriculture, forestry, and fisheries.

#Island Biogeography and Evolution: Darwin's Finches 🐦

#The Galapagos Islands Example

• Initial Colonization: A small group of finches from Ecuador was blown to the Galapagos Islands.
• Limited Immigration: Due to the distance from the mainland, there was little new immigration.
• Adaptive Radiation: The finches evolved into many different species, each adapted to different food sources and habitats.

#Evolutionary Drivers

• Natural Selection: Different islands had different environmental pressures, leading to different adaptations.
• Geographic Isolation: Each island acted as its own evolutionary laboratory, resulting in unique species.

#Final Exam Focus 🎯

#High-Priority Topics

• Island Biogeography Theory: Understand the relationship between island size, distance, immigration, and extinction.
• Invasive Species: Know the characteristics of invasive species and their impacts on ecosystems.
• Endemic Species: Understand their vulnerability and importance in conservation.
• Evolutionary Concepts: Be able to explain how island biogeography can drive evolution.

#Common Question Types

• Multiple Choice: Expect questions that test your understanding of key terms and concepts.
• Short Answer: Be prepared to explain the factors that influence species richness on islands.
• Free Response: You might be asked to analyze the impacts of invasive species or explain how island biogeography relates to evolution.

#Last-Minute Tips

• Time Management: Don't spend too long on any one question. Move on and come back if you have time.
• Read Carefully: Pay close attention to the wording of each question.
• Use Diagrams: Draw diagrams to help you visualize concepts and explain your answers.
• Stay Calm: Take deep breaths and believe in yourself. You've got this!

#Practice Questions

Practice Question

#Multiple Choice Questions

1. Which of the following best describes the relationship between island size and species richness? (a) Larger islands tend to have fewer species due to increased competition. (b) Smaller islands tend to have more species due to reduced predation. (c) Larger islands tend to have more species due to greater habitat diversity. (d) Island size has no significant impact on species richness.

2. An invasive species is most likely to have which of the following characteristics? (a) A narrow ecological niche and a high dependency on specific resources. (b) A high number of natural predators in its new environment. (c) A broad ecological niche and the ability to thrive in various conditions. (d) Slow reproduction rates and limited dispersal capabilities.

3. The concept of adaptive radiation is best illustrated by which of the following examples? (a) The extinction of endemic species due to habitat loss. (b) The evolution of Darwin's finches on the Galapagos Islands. (c) The introduction of invasive species into a new ecosystem. (d) The migration of a single species across different continents.

#Free Response Question

Part A (3 points): Describe the key factors that influence the equilibrium number of species on an island, according to the Island Biogeography Theory.

Part B (3 points): Explain how the introduction of an invasive species can disrupt the equilibrium of an island ecosystem.

Part C (3 points): Discuss how the principles of island biogeography can be applied to the design of nature reserves on continents.

Scoring Breakdown:

• Part A:
  • 1 point for identifying island size as a factor.
  • 1 point for identifying island distance from the mainland as a factor.
  • 1 point for explaining the role of immigration and extinction rates in reaching equilibrium.
• Part B:
  • 1 point for explaining that invasive species often lack natural predators.
  • 1 point for explaining that invasive species often outcompete native species for resources.
  • 1 point for explaining that invasive species can alter habitats and disrupt the ecosystem.
• Part C:
  • 1 point for explaining that larger reserves can support more species.
  • 1 point for explaining that reserves connected by corridors can increase immigration.
  • 1 point for explaining that reserves should be designed to minimize edge effects and habitat fragmentation.

Alright, you've got this! Review this guide, take a deep breath, and go crush that exam! You're more prepared than you think. Good luck! 🍀