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Biology Assignment: Article Review On Microplastic Contamination Of Wild & Captive Flathead Grey Mullet


Task: Study the article entitled “Microplastic contamination of wild and captive flathead grey mullet (Mugil cephalus) by Cheung et al., (2018) and complete the following biology assignment questions:


1. Based on your understanding, can you distinguish the paper is “basic research” or “applied research”? Explain your answer.
Ans. Basic research with regards to the case scenario of biology assignment is generally applicable for natural phenomena, specifically for natural science. It is also called fundamental knowledge as it emphasizes the focus on advancing scientific knowledge for understanding a certain topic even better. In short, information gained for the purpose of increasing knowledge is called basic research. This type of research is based on a theoretical explanation of basic principles and theories to be tested on a certain topic. Understanding the basic law is the motive of conducting such research. Basic research helps to generalize and formulate theories about human behavior. The information collected through this research is usually universal in nature and has the same applicability. Hence, in simple words, basic research is the process followed to add new knowledge to the already existing one. On the other hand, applied research is something opposite to basic research. Rather than theoretical explanation, it focuses on real life applications of natural sciences. The main motive of conducting such research is to find unique solutions to practical problems and develop innovative technologies. In short, this research is only suitable for practical applications. It related the results of the study of a particular circumstance to the corresponding one of it. This research focuses on situations that are facing a certain business problem. Also, applied research can be defined as the research focused on ascertaining political, social and economic trends. The type of research required to be conducted depends on the level and purpose of its conduction. If the purpose is to add certain scientific knowledge, basic research must be applied. Whereas, when the purpose is to find a suitable solution to a certain problem, applied research must be conducted. Based on the understanding of the provided article, it can be concluded that it is applied research (Cheung, Lui and Fok, 2018). The article is based on practical experiments with grey mullets and white mullets and it aims to find a solution to a specific scientific problem.

2.Based on the content of paper, in your opinion, list FOUR problems commonly faced by researchers to conduct the research
Ans. The challenges researchers might have faced while conducting the applied research are-
Ethical challenge- Applied researches are supposed to be carryout out specifically in naturalistic settings. Hence, researchers generally have to deal with some ethical problems that make the research difficult. Ethical dilemmas may arise regarding some privacy or informed consent matters. In some researches, participants may feel pressured or coerced into participation. This can happen in studies conducted by industrial-organizational psychologists as a condition of their employment. These problems can sometimes even affect the result studies.
Validity challenges- Since applied research is focused on real life problems, researches need to take place in practical fields. It is not possible for any human being to have complete control over natural variables. Extraneous variables can have some influence on the research that can affect the final results even without the consideration or realization of the experimenters. People working in applied research are generally very concerned about the external validity of their work. As the results of scientific researches are supposed to be utilized directly in real life problems. Researchers put efforts to affect not only the participants with the results but also a larger population outside the lab. Hence, external validity is of particular importance in this type of research.
Availability challenge- As said before, no human being can have control over nature. Hence the availability of required materials is uncertain. The particular material required for the experiment may not be available right at the time.
Fraudulent findings- Some researchers feel the pressure of producing positive results in certain situations. But the results depend on the practical experiments. Hence, this kind of pressure may distort the actual result and lead to the publishing of fraudulent ones.

3. What is its experimental design to carry out study microplastic contamination in grey mullet (i.e. sampling strategy)? What kind of sampling method used by the authors?
Ans. The experimental process started with the mixing of retracted stomach and intestine portions with 400 ml out of 30% hydrogen peroxide. This process leads results in the digestion of the organic matter. After completion of the digestion process, the dissolved solution was retained. Following this, saline made the filtration and separating the density in plastic particles happen. The density of the solution was increased by adding 800 ml saturated NaCl solution to it. After keeping it overnight, the difference in densities made the floatation of plastic particles separate from the dissolved tissue solution. After this, the solution was put into filtration under Whatman Grade 1 filter paper and kept in clean dishes. Thus, it was ready for microscopic observation. After observing under a stereomicroscope, the plastic particles were recognised and stored in form of image for further experiments. The observed plastic was classified as fibres, which had elongated shapes; fragments that seemed as debris of large plastics and sheets that were observed as thin layers of plastic. The observations about the length and colours of the plastics were recorded (Cheung, Lui and Fok, 2018). Plastics identified under different physical categories were randomly tested and sampled with particular sampling accessories. After all these, enough care was taken for the laboratory accessories to avoid contamination.

For the samples of this research, the researchers purchased 60 flathead grey mullets from a fish market in Hong Kong. out of these, they collected 30 wild mullets’ inhabitants of eastern coats of Sam Mun Tsai and 30 captive mullets around the local ponds. They measured 0.1 gm and 0.1 cm to be the fork length along with weight of each sample. The researchers applied ventral dissection on the samples and removed the stomach and intestines from them. The tissue was then kept in the refrigerator for further process.


4. Study the following table excreted from the paper. Answer the question:

Comment ANY FIVE shortcomings of data presentation in Table 1
Ans. The table provided gives a statistical description of the mullet samples collected by the researchers. The total sample size is 60 flathead grey mullets where 30 are wild and 30 are captive. The table also provides an insight into the mean, median, standard deviation and interquartile range of the sample. The table has two parts, one describes the statistical analysis of wild mullets and the other part describes about the captive mullets. First discussing about the wild mullet, the number of plastic items found in them after the experiment has a mean of 4.30. The same has the median of 1, the standard deviation of 14.5 and the interquartile range of 2.25. Next, the mean for the size of plastics found in millimeters is 1.21, the median is 0.975, the standard deviation is 0.833 and the interquartile range is 1.08. The length of the wild mullet in millimeter has a mean of 433, median of 431 and an equal standard deviation and interquartile range of 104. The mean, median, standard deviation and interquartile range for fish wight in grams are 765, 766, 104 and 106 respectively. And the same for tissue weight are 39.4, 37.7, 9.60, 15.2 respectively. Coming to the discussion of captive mullet, the mean, median, standard deviation and interquartile range for the number of plastic items found are 0.20, 0, 0.48 and 0 respectively. Next, the same statistical data for the size of plastic items are 1.05, 0.10, 0.15 and 0.875 respectively. Similarly, the table shows the statistical details for fish length, fish weight and tissue weight of captive mullets. However, there are certain drawbacks to this type of tabular data presentation. This puts limited focus on individual items, gives no scope for description, requires expert knowledge to understand, presents only conclusion rather than explanation and any qualitative expression is not possible through this kind of presentation.

5. In your opinion, can you identify independent variable, dependent and controlled variables based on the research questions mentioned in the paper. Explain briefly.

Research question

Independent variable

Dependent variable

Controlled variable

Does the amount of microplastic in grey mullet collected in wild type higher than in the aquaculture?


Aquaculture can be considered as the independent variable. Generally, aquaculture does not depend on any other variable for its functioning. Also, it cannot get influenced by the functions of other variables. Aquaculture operates by itself and has its own results. Hence, they are called the individual variables in researches.  

In this column, grey mullet is the dependent variable. Grey mullet alone cannot make a research successful. The results of the research depend on the amount of mullet and the situation of aquaculture. Because grey mullet alone is of no use and they require other variables to perform, they can be considered as the dependent variable. 

Under the controllable variable column, microplastic is the suitable name. The previous two variables, that is, aquaculture and grey mullet cannot be controlled because they are natural factors. But the presence of microplastics in them can be controller following certain measures.  

Does the types of microplastic in wild type grey bullet less than the samples collected in the aquaculture?


In this case too, aquaculture is the independent variable. Microplastics, grey mullet or any other variable cannot affect the existence of aquaculture. Even with any changes in other variables, aquaculture remains stable. It is difficult or rather impossible to influence the function of aquaculture.  

The dependent variable is the one that cannot function alone without depending on any other. Grey mullet is the one that cannot function without the knowledge of its amount and the situation of aquaculture. To get the desired result of a research, grey mullet must have the back of its amount and aquaculture.  

Microplastic is the controlled variable. Out of the three, only microplastic is the one that can be controlled by some precautions. The other two being natural factors, cannot be controlled by anyone. Hence, only microplastic is the one.


Cheung, L.T., Lui, C.Y. and Fok, L., (2018). Microplastic contamination of wild and captive flathead grey mullet (Mugil cephalus). Biology assignment International journal of environmental research and public health, 15(4), p.597.


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