Unit 8 FRQ (Invasive Species)

AP Bio Unit 8 FRQ: Invasive Species

Understand the Ecological Impact of Invasive Species on Native Communities

👋 Welcome to the AP Bio Unit 8 FRQ (Invasive Species).
These questions are longer, so grab a pen and paper or open up a blank page on your computer to jot down your answers.

⏱ Time Management Tip: Remember, you will have 6 free-response questions on the AP Biology exam, and you’ll have 90 minutes to complete all of them. This means you should allocate about 15 minutes per FRQ.

🤔 Need a quick refresher? Check out the Unit 8 Overview for important concepts about population dynamics and ecosystem interactions.

😩 Stuck halfway through answering? Explore all available Unit 8 resources for more support.

Scenario

Crepe myrtles, or Lagerstroemia, are popular ornamental trees used in landscaping because of their quick growth and aesthetically pleasing foliage. They are fast-growing and resistant to most diseases. Crepe myrtle bark scale (CMBS) is an insect that infects crepe myrtles, covering them with a felt-like gray surface and boring into the bark to consume sap. The CMBS excretes a black substance called “sooty mold” that coats the bark of infected trees, leading to damage and decreased photosynthesis. Initially found in Dallas, Texas in 2004, CMBS rapidly spread to Arkansas and Tennessee by 2014 and 2013, respectively, and shows no signs of slowing its expansion.

Questions

(a) Identify the type of growth CMBS are currently experiencing across the southern United States.

Response Guide:

• Growth Type: Exponential Growth
  • CMBS is currently experiencing exponential growth across the southern United States. This type of growth is characterized by a rapid increase in population size without apparent environmental constraints, which allows the population to double at a consistent rate.

(b) Describe the relationship between the crepe myrtle trees and CMBS.

Response Guide:

• Relationship Type: Parasitism
  • The relationship between crepe myrtle trees and CMBS is parasitism. The CMBS benefits by feeding on the sap of the crepe myrtle trees, whereas the crepe myrtles are negatively affected as their sap is depleted and they suffer from reduced growth and vitality due to decreased photosynthesis.

(c) On a half-acre lot of land, there is an estimated population of 1,467 CMBS. The per capita birth rate over one month is 0.14, and the per capita death rate is 0.06. Calculate the per capita growth rate of the population. Round your answer to the nearest hundredth.

Response Guide:

• Calculation:
  • Per Capita Growth Rate (r) = Birth Rate (b) – Death Rate (d)
  • $r = 0.14 – 0.06 = 0.08$
  • Answer: 0.08
  The per capita growth rate of the population is 0.08, indicating a positive growth rate in the population over the month.

(d) Neonictinoids are insecticides that can be placed on the ground around CMBS infestations because trees absorb the substance into their vascular systems. Identify the property of water that allows neonictinoids to be absorbed, and describe the change in the type of growth of CMBS you would expect to see shortly after.

Response Guide:

• Property of Water: Cohesion and Adhesion
  • Cohesion allows water molecules to stick to each other, while adhesion allows them to stick to the walls of the xylem vessels. These properties enable the upward movement of water and dissolved substances like neonictinoids in the plant vascular system.
• Expected Growth Change:
  • After the application of neonictinoids, CMBS populations are expected to undergo a change from exponential growth to a logistic growth model, or even a decline. The insecticide will reduce the population by increasing the mortality rate, resulting in fewer individuals and thus limiting further expansion of CMBS.

(e) A neighboring lot of land has a Simpson’s diversity index of 0.74. The lot infected by CMBS has a Simpson’s diversity index of 0.49. Explain what this difference in indices means.

Response Guide:

• Simpson’s Diversity Index Explanation:
  • Simpson’s Diversity Index measures the diversity of species within an ecosystem, with values ranging from 0 to 1, where values closer to 1 indicate greater diversity.
• Difference in Indices:
  • The neighboring lot with a Simpson’s index of 0.74 has a higher biodiversity, indicating that it contains a wider variety of plant and animal species. In contrast, the CMBS-infested lot with an index of 0.49 has reduced biodiversity. The infestation of CMBS may have contributed to a decline in the variety of species by limiting the health and growth of crepe myrtles, reducing habitat availability, and allowing fewer species to thrive.