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INSTRUCTIONS

1. Thefrontpageofyouranswersheetmustinclude: a. Yourname
b. Yourstudentnumber
c. The signed plagiarism declaration
2. ThisactivitycomprisesTWOsections
Section A: Experiment-based questions.
Section B: Essay Question.
3. Completeallquestionsintheorderthattheyarepresentedtoyou.
4. ThemaximummarkforthisSBAis50.
5. The answers MUST be handwritten on an exam pad and submitted.
6. YouhaveONEWEEKtocompletethisSBA.
7. If you have used any sources to answer questions, please put the
information in your own words. If needed, include a reference list at the end of your paper to avoid plagiarism.
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SECTION A QUESTION 1
Determining population size
Tiara and Xavier want to determine the oyster population size in the rock pools at their local beach (see Figure 1 below). Oysters are sessile marine invertebrates that attach themselves to rocks. The rock pools have a total surface area of 28 m2.
Question 1.1 [3 marks]
Tiara and Xavier both agree that the quadrat method would work best. Explain why you
agree. Explain why you would not choose to use the mark and recapture method.
Question 1.2 [4 marks]
The quadrat they will be using is 2 m2 and they choose to throw the quadrat four times at random at different locations along the 28 m2 rock pool. The results are recorded in the table below. Using these results, calculate X and Y. Show all workings, and round off to the nearest whole number.
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Throw number
Number of oysters in a quadrat
1
21
2
9
3
27
4
15
Total
X
Population size
Y
Question 1.3 [2 marks]
How have (a) validity and (b) reliability been assured in this experiment?
Question 1.4 [4 marks]
Describe any four precautions that must be considered when working with
the mark and recapture method.
QUESTION 2
[Question 1: 13 marks]
You will need a paperclip to complete this question and print out the aerial photograph of the park below.
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Information:
The population of tulips in a park will be determined by many factors: temperature, frequency of lawn being cut and the number of people that use the park. The potential population size in a given month will be due to the physical factors that go hand in hand with the seasons.
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There are many tulip species with a lot of variety: some are annuals, others are perennials, and their petals can be white, orange, or other colours. While tulips come in many colour combinations, you have a tulip with white petals.
The Parks and Recreation Department wants to increase the biodiversity in its parks. They need to know the number of tulips in the parks to estimate how many herbivores, like moles, they can support. They collect data every month but only need this month's data.
Use the following method to provide them with December’s data.
Method:
1. Take a paperclip and completely straighten it.
2. Bend the paperclip into the best square (quadrat) you can manage. Use the whole paperclip.
3. The quadrat now represents 1m2.
4. Take the aerial photo of the park provided below and cut the corners out, using solid lines as a guide.
5. Now bend up the edges on the dotted lines to form a border around your park.
6. Place your quadrat in the park.
7. Close your eyes and shake your park so the quadrat will rest in a random spot.
8. Stop shaking your park and open your eyes.
9. Mark the middle of the quadrat with a small “x”
10. Each white spot in the park represents a tulip. Count the tulips in the quadrat carefully and accurately.
11. Record your total in the rough table below.
12. Repeat steps 6) to 10) five times.
Rough work table for Quadrat sampling.
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Question 2.1 [3 marks]
Calculate the average of your counts. Record the data in December’s block. Show all
workings. Round off your answer to the nearest whole number.
Question 2.2 [3 marks]
Table showing the average number of tulips per square metre over twelve months
in the park.
Complete the table above by adding the missing variables (a) and (b). Question 2.3 [2 marks]
Identify the dependent variable in this experiment.
Question 2.4 [1 mark]
Identify the independent variable in this experiment.
Question 2.5 [2 marks]
What is the aim of this investigation?
Question 2.6 [4 marks]
What two variables were controlled in this experiment? How was each variable fixed?
(a)
Jan ‘23
Feb ‘23
Mar ‘23
Apr ‘23
May ‘23
Jun ‘23
Jul ‘23
Aug ‘23
Sep ‘23
Oct ‘23
Nov ‘23
Dec ‘23
(b)
42
33
41
20
12
5
2
15
13
22
31
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Question 2.7 [2 marks]
Suggest one step in the method that could be improved to make the results more
accurate. In your answer, refer to the letters of the steps of the method.
[Question 2: 17 marks]
SECTION B QUESTION 3 Question 3 [20 marks]
Logistic S-shaped growth is normally found in higher-order organisms (e.g. mammals), which typically reproduce slower. Populations tend not to exceed the carrying capacity and, if they do, they show higher levels of resilience to environmental resistance.
The S-shaped graph constitutes varying phases, how many are they? Identify and extensively explain them.
Which two factors affect population growth?

1 answer

Answers

SECTION A

Your name: [Your Name]
Your student number: [Your Student Number]
Plagiarism Declaration: I hereby declare that this work is my own and that I have not committed plagiarism in any form.

QUESTION 1

Question 1.1 [3 marks]

The quadrat method is suitable for determining the oyster population size because oysters are sessile organisms, meaning they do not move from their attached positions. The quadrat method allows researchers to sample a specific area, calculate population density, and extrapolate that information to estimate total population size. On the other hand, the mark and recapture method is not appropriate for oysters due to their stationary nature. This method is better suited for mobile organisms and could result in inaccurate population estimates due to low recapture rates and movement of the organisms.

Question 1.2 [4 marks]

To calculate X (the total number of oysters) and Y (the population size), we first need to sum the number of oysters found in each quadrat:

  • Throw 1: 21 oysters
  • Throw 2: 9 oysters
  • Throw 3: 27 oysters
  • Throw 4: 15 oysters

Calculating X: \[ X = 21 + 9 + 27 + 15 = 72 \text{ oysters} \]

Calculating Y (Population Size): To estimate the total oyster population size (Y) in the 28 m² rock pool, we need to use the area of the quadrat (2 m²) and the total area (28 m²):

Population Density = \( \frac{X}{\text{Number of quadrats}} \) \[ \text{Population Density} = \frac{72 \text{ oysters}}{4 \text{ quadrats}} = 18 \text{ oysters/m}^2 \] Now multiply by the total area of the rock pool: \[ Y = 18 \text{ oysters/m}^2 \times 28 \text{ m}^2 = 504 \text{ oysters} \]

Question 1.3 [2 marks]

(a) Validity has been ensured by using random sampling, which helps eliminate bias in selecting quadrat locations, providing a more accurate representation of the oyster population.
(b) Reliability is assured by repeating the quadrat throws multiple times, which provides a larger sample size and helps ensure consistent results that can be replicated.

Question 1.4 [4 marks]

  1. Timing of Capture: Oysters should ideally be captured during the same tidal conditions to avoid discrepancies in population estimates due to different habitats exposed during varying tides.
  2. Marking Technique: The method of marking should not harm the oysters, ensuring survivability and accuracy in recapture.
  3. Weather Conditions: Conducting experiments during favorable weather conditions to minimize stress on the organisms and avoid bias in recapture.
  4. Sampling Frequency: The number of recapture attempts should be standardized to ensure statistical validity and improve the reliability of the data.

QUESTION 2

Question 2.1 [3 marks]

Let's assume the total counts over five trials were as follows:

  • Trial 1: 10 tulips
  • Trial 2: 8 tulips
  • Trial 3: 12 tulips
  • Trial 4: 9 tulips
  • Trial 5: 11 tulips

Calculating the average: \[ \text{Average} = \frac{10 + 8 + 12 + 9 + 11}{5} = \frac{50}{5} = 10 \] So December’s count would be recorded as 10 tulips.

Question 2.2 [3 marks]

(a) Average number of tulips per square metre in December: 10
(b) To be determined according to the data from previous months.

Question 2.3 [2 marks]

The dependent variable in this experiment is the number of tulips counted within the quadrat.

Question 2.4 [1 mark]

The independent variable in this experiment is the time of year (month).

Question 2.5 [2 marks]

The aim of this investigation is to assess the population size of tulips in the park to inform biodiversity management and support herbivore populations.

Question 2.6 [4 marks]

(a) Two variables that were controlled in this experiment include:

  1. Size of the quadrat: Always using a 1m² quadrat to ensure consistency in sampling area.
  2. Timing of counts: Conducting counts during similar weather conditions to reduce variability in tulip visibility due to external factors.

Question 2.7 [2 marks]

One step that could be improved is the counting process; instead of counting tulips manually each time, researchers could utilize a digital counter to improve accuracy and reduce human error.

SECTION B

Question 3 [20 marks]

The S-shaped (logistic) growth curve consists of four phases:

  1. Lag Phase: In this initial phase, the population is small, and individuals are acclimatizing to their environment. Growth is minimal as reproduction begins slowly.

  2. Exponential Growth Phase: As resources become plentiful and individuals adapt, the population exhibits rapid growth, often leading to doubling over short periods. This phase reflects the potential reproductive capacity of a species.

  3. Decelerating Growth Phase: As the population approaches the carrying capacity of the environment, resources begin to become limited. The growth rate starts to slow down as competition for resources increases.

  4. Stable Equilibrium Phase: Eventually, the population stabilizes, oscillating around the carrying capacity (K). Here, birth rates decline and death rates increase until equilibrium is reached.

Two factors affecting population growth:

  1. Biotic Factors: These include competition, predation, parasitism, and disease, which can limit the population size and affect reproduction rates negatively.

  2. Abiotic Factors: Non-living factors such as climate, availability of water, temperature, and nutrients can influence the health of the environment and population growth rates by affecting the resources available for survival and reproduction.

Reference List

[If applicable, list any references used here.]