AICE Marine Science AS Practical Skills Day 6

Day #6. Lesson plan

As teachers, we continually seek engaging and effective ways to help our students grasp complex scientific concepts. One such area in marine science is the various sampling techniques used to estimate population sizes and study biodiversity. In this blog post, we’ll delve into two essential methods: the mark-release-recapture method and random sampling using a quadrat. We’ll also discuss their limitations to ensure our students develop a well-rounded understanding.

Lesson

• How Ocean Acidification Affects Marine Organisms-cont. (15 minutes)
  • Students will conduct observations, pH measurement and record shell weight for control and experimental group.
  • Students will record all data and observations.
• Bell ringer #6
• Use Student Guided Notes– This year, I’m using Version B Guided Notes with my students, as I’ve noticed they benefit from having more structured support during class.
• Lecture/Notes (PPT – slides 28 – 35)
  • this lesson covers section 4 of Chapter 4 Populations and sampling techniques: the method of mark-release-recapture and the limitations to the method, examples of calculations using data collected using this method, description of random sampling with examples and description of systematic sampling with real world examples. Below is a snippet of the PPT.

• Mark-Release-Recapture Method
  • The mark-release-recapture method is a widely used technique in ecology for estimating animal populations. This method is particularly useful for studying mobile and elusive species, such as fish, turtles, and other marine organisms.
  • Procedure:
    Capture: A sample of the population is captured, counted, and marked in a harmless way.
    Release: The marked individuals are then released back into their habitat and given time to mix with the unmarked population.
    Recapture: After a certain period, another sample is captured. The number of marked individuals in this second sample is recorded.
    Estimation: Using the proportion of marked to unmarked individuals in the second sample, the total population size is estimated using the formula:
    • N = n1xn2/m
    • N = estimate of population size
      n1 = number of individuals captured in first sample
      n2 = number of individuals (both marked and unmarked) captured in second sample
      m = number of marked individuals recaptured in second sample
      •This formula will be provided on the exam.
  • Limitations
    Assumption of Random Mixing: The method assumes that marked individuals mix randomly with the population, which may not always be the case.
    Behavioral Changes: Marking can sometimes alter the behavior of the organisms, making them more or less likely to be recaptured.
    Tag Loss: Marks or tags can be lost over time, leading to inaccurate counts.
    Population Changes: The population may change due to births, deaths, immigration, or emigration between the marking and recapture phases.
• Random Sampling Using a Quadrat
  • The quadrat method is an effective way to study the distribution and abundance of organisms in a defined area. It’s particularly useful for sessile or slow-moving organisms like corals, seaweeds, and small invertebrates.
  • Procedure
    Define the Study Area: Select and map the study area where sampling will occur.
    Place the Quadrats: Randomly place quadrats (usually square frames) within the study area.
    Count and Record: Count the number of individuals of each species within each quadrat and record the data.
    Analyze: Use the data to estimate population density and distribution patterns across the study area.
  • Limitations
    Random Placement: Ensuring truly random placement of quadrats can be challenging, and biased placement can affect the results.
    Sample Size: The number of quadrats sampled can influence the accuracy of the population estimates. Too few samples may not represent the entire population accurately.
    Edge Effects: Organisms at the edges of quadrats may be counted inconsistently, leading to errors in data collection.
    Environmental Variability: Differences in habitat within the study area can influence organism distribution, making it difficult to generalize results.
• Random Sampling: Imagine dipping a net into the ocean without any predetermined pattern or bias. Random sampling involves selecting sample points purely by chance, ensuring that each area has an equal probability of being chosen. This method helps in capturing a broad representation of marine habitats and organisms, minimizing the risk of skewed results due to human influence.
• Systematic Sampling: Contrastingly, systematic sampling involves selecting sample points at regular intervals or according to a predetermined pattern. For instance, sampling every 100 meters along a coastline or every hour at a specific depth interval. This method provides a structured approach that can be useful for studying trends or changes over time in a systematic manner.
• Small group activity – Example Questions for Calculating Populations Using the Mark-Release-Recapture Method
  • Question 1:
    A team of marine biologists is studying a population of crabs in a coastal lagoon. They capture, mark, and release 150 crabs. A few days later, they recapture 120 crabs and find that 30 of them are marked. Calculate the estimated population size of the crabs in the lagoon. (Answer: The estimated population size of the crabs in the lagoon is 600.)
  • Question 2:
    In a study of a local fish population, researchers capture and mark 200 fish. After releasing them back into the ocean, they wait for a week and then recapture 250 fish, of which 50 are marked. Calculate the estimated population size of the fish. (Answer: The estimated population size of the fish is 1000)
  • Question 3:
    A researcher is estimating the number of starfish in a tide pool. They capture, mark, and release 75 starfish. Two days later, they recapture 100 starfish, finding 15 of them marked. Calculate the estimated population size of the starfish in the tide pool. (Answer: The estimated population size of the starfish in the tide pool is 500)
  • Question 4:
    Scientists are studying a population of sea urchins. They capture, mark, and release 60 sea urchins. After some time, they recapture 80 sea urchins and find that 20 of them are marked. Calculate the estimated population size of the sea urchins. (Answer: The estimated population size of the sea urchins is 240)
  • Question 5:
    During a survey of a mangrove swamp, ecologists capture and mark 120 shrimp. They release them and later recapture 150 shrimp, finding that 25 are marked. Calculate the estimated population size of the shrimp. (Answer: The estimated population size of the shrimp in the mangrove swamp is 720)

Homework – high level/flipped classroom

• Version A – For High-Level Students:
  Ideal for independent or advanced learners, this version requires students to copy all notes by hand as homework before class. This flipped-learning approach helps students come to class prepared, freeing up time for application activities, discussions, and AICE-style practice questions.
• For this assignment have students fill in the blanks using the PPT Presentation.

By incorporating these methods into your curriculum, you can provide students with practical skills and a deeper understanding of ecological research. They’ll learn not only how to collect and analyze data but also how to critically assess the reliability and limitations of their findings.

Happy Teaching!

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