Asia-Pacific Forum on Science Learning and Teaching, Volume 8, Issue 2, Article 5 (Dec., 2007)
Gülcan ÇETİN
English and Turkish pupils’ understanding of decomposition

Previous Contents Next
Results and Discussion

After in depth examination of the students' responses to four diagnostic questions related to decomposition in different everyday contexts, seventh grade students' levels of understanding of decomposition were presented in three sections: decomposition of organic molecules, decomposition of biodegradable materials and non-biodegradable materials, and a general contrast of students' levels of understanding about decomposition.

Decomposition of organic molecules

To assess the students' understandings of decomposition of organic molecules, Question 1-3 was asked. Decomposition of organic molecules was also associated with other concepts: decomposition in environment, and producer, consumer and decomposer relationships in the cycle of materials.

Question 1 was multiple-choice question required reasoning and the aim of the question was to analyze patterns of students' understandings about decomposition of organic molecules by micro-organisms in an ecosystem relating to the other concepts: producer, consumer, decomposer, recycle, and ecosystem. This question might contain the main idea: micro-organisms broke down organic, dead plants/animals, or they fed on organic materials. The students were expected to explain this question as three science teachers had taught ecosystem, decomposition, and decay. This probe was also referred to the concept of recycle that the students were familiar with this concept in everyday life too. Table I shows the students' levels of understanding of students' ideas for the first question.

According to Table I, a small minority of children gave some explanations with sound understanding relating to micro-organisms, for example micro-organisms like bacteria fed on the organic molecules and rot them away (27.7% English students and 14.2% Turkish students). The English students' level of misunderstanding was higher than the Turkish students (31.4% and 8.2%) assuming consumers, producers, and soil were responsible for breaking down complex molecules in an ecosystem in general. Students' level of no understanding was too high (39.2% English students and 65.3% Turkish students).

Table I: A Summary of Students' Levels of Understanding for their Ideas and their Percentage as a Response to Question 1

Understanding Categories of Students' Ideas

ES %

TS %

A. Sound Understanding

27.4

14.2

Explanations relating to micro-organisms:

  • They fed on the organic molecules and rot them away.

13.7

2.0
  • They ate (broke down) all the dead materials.
7.8
 12.2
  • They waved though the soil to break down complex molecules.
5.9 0

B. Partial Understanding

2.0

12.3

Explanations relating to micro-organisms:

  • They were bacteria.

0

8.2
  • They ate everything.
2.0 0
  • Bacteria produced carbon dioxide and minerals.
 0 4.1

C. Misunderstanding

31.4

8.2

Explanations relating to producers:

  • Because producers made photosynthesis to make carbon dioxide available. When they died, they produced minerals.

2.0

0
  • Because producers used the carbon dioxide and mineral ions for photosynthesis.
2.0 0
  • Because plants reproduced their food.
2.0

0
  • Because producers were the source of a food chain.
 2.0 0

Explanations relating to consumers:

  • Because consumers ate molecules, animals, or plants.
 9.5 0
  • Because humans were main responsible part for breaking down in an ecosystem.
2.0
 3.7
  • Because consumers passed their energy onto predators.
 0 2.3

Explanations relating to micro-organisms:

  • Micro-organisms broke down the soil when they digested it.

2.0

2.2
Explanations relating to soil:
  • Because soil broke down everything natural.
 3.9 0
  • Because producers could not grow without soil.
 2.0 0
  • Because soil was not rich in vitamins and minerals.
 2.0 0
  • Because when plants died they broke down into the soil to fertilize the ground. So the system could start again.
 2.0 0

D. No Understanding

39.2

65.3
  • Non-sense
 9.8 6.1
  • Rewrite
 13.7 26.5
  • No response
 15.7 32.7

(ES: English Students, n=54; TS: Turkish Students, n=42)

Question 2 was multiple-choice question required reasoning part and the aim of the question was to analyze children's ideas on key concepts of decay and carbon cycle related to other concepts: photosynthesis, evaporation, and reproduction. This probe was designed for how students understood the release of carbon compounds from plants after death. The main idea for Question 2 might include that carbon compounds were released from dead plants through micro-organisms ate them. The categories of responses are provided below in Table II on the basis of levels of understanding.

As seen in Table II, the students' partial understanding about this question was higher than the students' sound understanding, with more English students (26.8%) showing a partial understanding than the Turkish students (11.1%) according to the results of the Question 2. The students' level of misunderstanding was too high (32.1% English students and 15.6% Turkish students), and one striking point here was the explanation relating to evaporation: “When a plant died, the carbon and water were released by evaporation” (16.1% English students). The level of no understanding had the highest level of understanding among other categories (39.3% English students versus 66.6% Turkish students).

Question 3 was an open-ended question, and it was set to find out students' ideas on decomposition related to decomposer, decomposition of natural or organic materials. Two main ideas for the response to the question might be: the apples had a bad smell and they loose their original shape because they rot (or they loose their original shape because they loose moisture and dried up), they smelt because of gas being given off a result of decay, and they became soft and collapsed because of decay. The students had a wide rage of responses, and they explained their ideas by either giving separate reasoning for loosing shape and having bad smell of apples, or giving general comments (See Table III).

Table II: A Summary of Students' Levels of Understanding for their Ideas and their Percentage as a Response to Question 2

Understanding Categories of Students' Ideas

 ES

  %

TS

%

A. Sound Understanding

1.8

6.7

Explanations relating to decay:

  • After plants died, they were decayed by micro-organisms.

1.8

6.7

B. Partial Understanding

26.8

11.1

Explanations relating to decay:

  • When plants died, they were decayed away to nothing leaving minerals and nutrients in the soil.

5.4

0
  • If plants were dead, they could not reproduce, photosynthesize, or evaporate.

16

8.9
  • Plants became part of the earth and soil.

5.4

2.2

C. Misunderstanding

32.1

15.6

Explanations relating to decay:

  • The oxygen would eat them and disposed of them.

1.8

0

Explanations relating to evaporation:

  • Carbon dioxide was a gas and it was with which could be rain.

1.8

0
  • When plants died, the carbon and water were released by evaporation.

16.1

2.2

Explanations relating to photosynthesis:

The water and the sun still produced photosynthesis.

1.8

0
  • After plants died, carbon compounds were released and they made photosynthesis. 

5.2

2.2
  • After plants died, photosynthesis let carbon compounds out.

0

6.6
  • Plants gave carbon dioxide out by photosynthesis.

0

2.2
  • Plants could not get carbon dioxide without photosynthesis. Thus, the carbon dioxide levels increased.

0

2.2

Explanations relating to reproduction:

  • The dying plants took in oxygen and passed out carbon dioxide when They were dead.

1.8

0
  • New plants seeded from the dead plant would produce carbondioxide in photosynthesis.

1.8

0
  • They were released because of the seeds.

1.8

0

D. No Understanding

39.3

66.6
  • Non-sense

0

4.4
  • Rewrite

33.9

31.1
  • No response

5.4

31.1

 (ES: English Students, n=54; TS: Turkish Students, n=42)

Table III: A Summary of Students' Levels of Understanding for their Ideas and their Percentage as a Response to Question 3

Understanding Categories of Students' Ideas

 ES

  %

TS

%

A. Sound Understanding

78.9

64.6

Explanations relating to the apples losing their original shape and having a bad smell:

  • Because they were put outside and decayed by micro-organisms (they were not kept in cool place or a fridge).
 0 18.7
  • Because the apples would start to decay by micro-organisms. The apples went soft and have a bad smell.
5.5 39.6

Explanations relating to the apples losing their original shape:

  • Because the apples were decayed by micro-organisms and started to shrivel up.

44.0

2.1
  • Because the apples' water was drying out by the sun. Thus, they loose air inside them and they shriveled up.

16.0

2.1

Explanations relating to the apples having a bad smell:

  • Because they were decaying.

13.4

2.1

B. Partial Understanding

9.4

24.8

Explanations relating to the apples losing their original shape and having a bad smell:

  • Because they loose molecules that kept them fresh and they had no food supply.

8.0

22.7

Explanations relating to the apples losing their original shape:

  • Because they loose their freshness and they were wrinkly.

0

2.1

Explanations relating to the apples having a bad smell:

  • Because moulds smelt bad.

1.4

0

C. Misunderstanding

6.3

2.2

Explanations relating to the apples losing their original shape and having a bad smell:

  • Because the sun looked away all the energy, so it died.

1.3

0
  • Because the vitamins and minerals were eaten by oxygen.

1.3

0
  • Because the atoms and molecules in the air attacked the apple and they caused decay after a while.

1.3

0

Explanations relating to the apples losing their original shape:

  • When air got inside of an apple, it caused to decay. Thus, the apple got small and wrinkly.

2.4

2.2

D. No Understanding

5.4

8.4
  •    Non-sense

0

0
  •    Rewrite

0

0
  •    No Response

5.4

8.4

(ES: English Students, n=54; TS: Turkish Students, n=42)

According to Table III, although students showed a high sound understanding, students demonstrated a fewer misunderstanding and no understanding. The English students' performances were much better than the Turkish students for this question. The number of the students' ideas indicating sound understanding was extremely high. The English students (78.9%) provided more sound understanding ideas compared to the Turkish students (64.6%). Many English students indicated that “the apples loose their original shape because the apples were decayed by micro-organisms and started to shrivel up”, while most Turkish students stated that “the apples loose their original shape and had a bad smell because the apples would start to decay by micro-organisms. They went soft and had a bad smell”. However, the Turkish students (24.8%) provided more partial understanding ideas compared to the English students (9.4%). One of the excellent points for the study both the Turkish students' ideas including misunderstanding (2.2%) and the English students' ideas including misunderstanding (6.3%) were the lowest level. Furthermore, the percentages of ideas showing no understanding were very low (5.4% for the English students and 8.4% for the Turkish students).

Decomposition of biodegradable materials and non-biodegradable materials

To assess the students' understanding of decomposition of biodegradable materials and non-biodegradable materials, the Question 4 was asked. It was an open-ended question. Also ecosystem, recycling, and environmental conservation were related to decomposition of biodegradable materials and non-biodegradable materials. This question included four main acceptable ideas: orange peels were biodegradable materials (natural or organic material); micro-organisms decomposed organic materials; tin cans were biodegradable materials; and micro-organisms did not decompose tin cans and they would rust.

As seen in Table IV, the students responded to Question 4 successfully indicating while micro-organisms decayed orange peels that were biodegradable (natural) material, micro-organisms could not decompose tin cans that were non-biodegradable and rusting could break down tin cans. However, it was observed that the English students' sound understanding level about this question was higher than the Turkish students' ideas (34.3% versus 11.1%). Moreover, both the English students' partial understanding and the Turkish students' partial understanding concerning the Question 4 were very high (48.6% English students versus 54.0% Turkish students). While the English students mainly stated that “tin cans were metal, so bacteria would not be able to eat them away (25.7% English students) and the Turkish students stressed out that “tin cans had stronger molecules in them and they did not soak up water” (19.0%). The present study had an agreement with the results of Malandrakis (2003), which showed that the children realized the role of sun, water and air in the decay of materials and their effect in increasing the speed of the decomposition process.

In Question 4, students' level of misunderstanding were considerably low for both samples (the English students 17.1% and the Turkish students 27.0%). Some students were not aware of micro-organisms could not decompose tin cans as tin cans were non-biodegradable materials. The students also mentioned “tin cans were decayed by bacteria in longer time than the orange peels” (the English students 17.1% versus the Turkish students 17.5%). However, students' level of “no understanding” was extremely low (the English students 0% versus the Turkish students 7.9%). These results of the current study were also in accordance with the study of Khatete (1995), which reported that the children were more familiar with decomposing of meat at home if the meat were not well preserved. He stressed that younger children tended to use mainly daily knowledge and experiences for responding to the questions. Children at school level 10 and 12 tended to give a wider variety of explanations although through more focused answers than those in years 5 and 8. This present study was in concurrent with the study results of Hellden (1992a) mentioned beforehand in theoretical framework session.

Table IV: A Summary of Students' Levels of Understanding for their Ideas and their Percentage as a Response to Question 4

Understanding Categories of Students' Ideas

ES

%

TS

%

A. Sound Understanding

34.3

11.1

Explanations relating to orange peels:

  • They were biodegradable (natural) materials.

24.8

11.1

Explanations relating to tin cans:

  • They were not biodegradable materials.

1.9

0
  • They could be broken by oxygen and water (rusting) but they did not rust easily.

7.6

0

B. Partial Understanding

48.6

54.0

Explanations relating to orange peels:

  • They were living things, but the tin cans were not.

5.8

9.6
  • They were soft and soaked up water.

1.9

11.1
  • They were more reactive than the tin cans.

1.9

0

Explanations relating to tin cans:

  • They were metal, so bacteria would not be able to eat them away.

25.7

14.3
  • They were hard, had stronger molecules in them, and they did not soak up water.

9.5

19.0

Explanations relating to insects:

  • They could not digest metal.

1.9

0

Explanations relating to insects, oxygen and water:

  • They ate away at orange peels.

1.9

0

C. Misunderstanding

17.1

27.0

Explanations relating to orange peels:

  • They entered the soil quickly, but the tin cans could not.

0

3.2

Explanations relating to tin cans:

  • Bacteria decayed them in longer time than the orange peels.

17.1

17.5

Explanations relating to nature:

  • Nature could not break down the tin cans in short time as they were much resistant to nature as they had hard materials.

0

6.3

D. No Understanding

0

7.9
  • Non-sense

0

1.6
  • Rewrite

0

0
  • No response

0

6.3

(ES: English Students, n=54; TS: Turkish Students, n=42)

In this study, one of the interesting results was that, although students should be familiar with the concepts of the recycle in everyday context, no students used one of these concepts of recycle to explain one of the four questions. Another reason might be the wording of the Question 1. One of the British teachers commented on this question and indicated that students would find it difficult “due to its wording”. According to the questionnaire, only one British science teacher taught the concept of carbon cycle. Therefore, this question was responded a few students. Leach (1995) also reached similar results stating while many older students used numerous factors to explain decay phenomena or causation of decay with age, they did not have a tendency to describe how various physical factors related to the action of micro-organisms and autolytic activity. In addition, students' aged in 5-16 did not give explanation that matter was entirely conserved and recycled in decomposition. Most of them referred to only the role of decay in the cycling of matter via the soil. On the other hand, some of students aged 7-16 mentioned about a partial conservation and cycling of matter as a result of enrichment of soil. In contrast, Malandrakis (2003) figured out that the children comprised the environmental consequences from the dispose of these materials and recycling as the most appropriate solution for them.

A general contrast of students' levels of understanding about decomposition

A summary of students' levels of understandings of decomposition could be given by using their percentages of occurrences in each group. The numbers of students' ideas obtained from the students' responses to each four question about decomposition. Although this study involved 54 English students and 42 Turkish students, the number of ideas of students generated for each question was not limited to one. These ideas indicated students' levels of understanding. Therefore, the percents were calculated for each levels of understanding counting their total numbers of occurrence for both samples. These percents were used to represent their distribution for both groups and to make more sound contrast in between. The results of this analysis were given in Figure 2. As an example, the total numbers of students' ideas indicating sound understanding were 142 for the English students and for 95 the Turkish students. The percents of the English students' sound understanding were 35 and the percents of the Turkish students' sound understanding were 24.

In general, there was a pattern emerging from the total numbers for different levels of understanding for each population. Figure 2 displays that the English students showed more promising results related to levels of sound understanding and no understanding of decomposition than the Turkish students. However, the Turkish students demonstrated high potential for the level of misunderstanding of decomposition. When the English and Turkish students had partial understanding they seemed to demonstrate parallel ideas in explaining decomposition.

Figure 2: Students' Levels of Understanding of Decomposition according and Overall Percent of the Students' Ideas for Each Level (Level of Understanding - SU: Sound Understanding, PU: Partial Understanding, MU: Misunderstanding, NU: No Understanding)

These emerging patterns were needed more explorations to see if there was a difference between the English and Turkish students' understanding levels of decomposition. The raw frequencies were tabulated for students' ideas of decomposition for each level of understanding as shown in Table V. A chi-square (X2) statistics were used to test the differences of the categories of data. In the previous examination, the English students appeared to perform better than the Turkish students in providing more ideas with higher levels of understanding levels of decomposition. The difference was significant, X2(3, N=798)=36.4, p≤0.001.

Table V: Frequencies of Understanding Levels for the English and Turkish Students' Ideas on Decomposition

Students

Level of Understanding

SU

PU

MU

NU

Total

English Students

142

87

87

84

400

Turkish Students

95

102

53

148

398

Total

237

189

140

232

798

(ES: English Students, n=54; TS: Turkish Students, n=42; Level of Understanding- SU: Sound Understanding; PU: Partial Understanding; MU: Misunderstanding; NU: No Understanding)

Çetin (2003) also emphasized that ninth grade Turkish students' sound understandings were increased in both experimental had a conceptual change approach instruction and control group had a traditional instruction after the ecology teaching. While there was a noticeable increase in students' partial understanding for the experimental group after the treatment, the control group students' partial understanding slightly decreased. There was a small increase in the experimental group students' partial understanding with misconceptions and a small decrease for the control group after the treatment. Students' misunderstandings were decreased for both experimental and control groups after the treatment, but the decrease was more for the students in the experimental group. Students' no understandings were decreased for both experimental group and control group after the treatment.

Copyright (C) 2007 HKIEd APFSLT. Volume 8, Issue 2, Article 5 (Dec., 2007). All Rights Reserved.