Tutor Niedino: Pri Science Questions and Concepts

[Tang]

Full.Cream:

think my boy was taught not to use 'regular' in description as it is too subjective.

Hi,


This is from my sister's i.science - Systems Primary 5 & 6 Textbook.


Cell wall - It is a strong and stiff structure which supports and gives the cell a regular shape.



And for my Science exam, I always prefer to use 'good shape'.

[Joy]

Hi atutor2001,


Teacher has final say.Case close, still answer is fixed and not rigid.She feels that she is right.

No one is able to clarify what is accepted in psle.thanks

Joy

atutor2001:

Leanne:

I got a reply from her teacher:

In Science, the specific meanings of the words is important.
Different adjectives means different things in Science.
According to Longman, the word rigid means \"stiff, not moving or bending\" - a movement.
However, we are looking for the inability of the cell to change shape - because it has been fixed by the cell wall.

He he he. The teacher's \"England very good.\" (Just added : \"fixed by the cell wall\" cannot be written as \"fixed cell wall\")

I have googled the common meanings of \"fixed\" shown below :
1. Firmly in position; stationary
2. established; settled; set (e.g. at a fixed time; a fixed price)

As for \"rigid\", the meanings are :
1. Not flexible or pliant; stiff
2. Not moving; fixed

Under normal usage, \"fixed\" used as an adjective often means (1) \"fastened - no change in position\" or (2) \"no change in quantity\". If we want to say that the shape of something does not change, then for clarity we should say \"cell wall has fixed SHAPE\".

Therefore, if we use the term \"fixed cell wall\", it could mean that the (1) position of the cell wall does not move, (2) the quantity of cell wall does not change. Science is rigorous - such alternative interpretations must be avoided.

On the other hand, \"rigid\" effectively means that the shape does not change. Therefore, it is more appropriate to use \"rigid cell wall\" if we want to communicate that the shape of the cell wall does not change.

In the good old days, my kids' science teachers hate me. They always got me wrong, thinking that I was hard up for the marks - explaining that it is difficult for them to change the marks after they were cornered. It really makes me mad when they give \"crab\" explanation without any thoughts at all - teaching the wrong concept.

[Mathmaniac]

Joy:

Hi atutor2001,


Teacher has final say.Case close, still answer is fixed and not rigid.She feels that she is right.

No one is able to clarify what is accepted in psle.thanks

Joy

atutor2001:

[quote=\"Leanne\"]I got a reply from her teacher:

In Science, the specific meanings of the words is important.
Different adjectives means different things in Science.
According to Longman, the word rigid means \"stiff, not moving or bending\" - a movement.
However, we are looking for the inability of the cell to change shape - because it has been fixed by the cell wall.

He he he. The teacher's \"England very good.\" (Just added : \"fixed by the cell wall\" cannot be written as \"fixed cell wall\")

I have googled the common meanings of \"fixed\" shown below :
1. Firmly in position; stationary
2. established; settled; set (e.g. at a fixed time; a fixed price)

As for \"rigid\", the meanings are :
1. Not flexible or pliant; stiff
2. Not moving; fixed

Under normal usage, \"fixed\" used as an adjective often means (1) \"fastened - no change in position\" or (2) \"no change in quantity\". If we want to say that the shape of something does not change, then for clarity we should say \"cell wall has fixed SHAPE\".

Therefore, if we use the term \"fixed cell wall\", it could mean that the (1) position of the cell wall does not move, (2) the quantity of cell wall does not change. Science is rigorous - such alternative interpretations must be avoided.

On the other hand, \"rigid\" effectively means that the shape does not change. Therefore, it is more appropriate to use \"rigid cell wall\" if we want to communicate that the shape of the cell wall does not change.

In the good old days, my kids' science teachers hate me. They always got me wrong, thinking that I was hard up for the marks - explaining that it is difficult for them to change the marks after they were cornered. It really makes me mad when they give \"crab\" explanation without any thoughts at all - teaching the wrong concept.

[/quote]Both the teacher's and atutor's explanations are correct. In fact, they are arguing about different things, if I interpret your posts correctly.

[atutor2001]

Below are just my views on the proper key words to use and the reasons :


Definitions

1. Plant cells have a regular shape. (instead of \"fixed shape\" because the shape of different parts of a plant can be different. On the other hand \"regular\" means the shape can form a pattern - which is true for all plant cells)

2. Plant cells have rigid cell wall. (instead of \"fixed\" because \"rigid\" highlights the main characteristic of cell wall, which is \"stiff\" i.e. giving it strength to support and act as \"skeleton\" for the plant. On the other hand, \"fixed\" is too general)

Functions of Cell Walls

1. To protect the cell.

2. To support the cell so as to give it / maintain a regular shape. (instead of \"fixed the shape of the cell\" because the shape of a plant cell can change a little if the vacuole is deprived of water - it will shrink and distort. So plant cell depends on both the cell wall and the vacuole to maintain its shape.)

[Tang]

atutor2001:

Below are just my views on the proper key words to use and the reasons :


Definitions

1. Plant cells have a regular shape. (instead of \"fixed shape\" because the shape of different parts of a plant can be different. On the other hand \"regular\" means the shape can form a pattern - which is true for all plant cells)

2. Plant cells have rigid cell wall. (instead of \"fixed\" because \"rigid\" highlights the main characteristic of cell wall, which is \"stiff\" i.e. giving it strength to support and act as \"skeleton\" for the plant. On the other hand, \"fixed\" is too general)

Functions of Cell Walls

1. To protect the cell.

2. To support the cell so as to give it / maintain a regular shape. (instead of \"fixed the shape of the cell\" because the shape of a plant cell can change a little if the vacuole is deprived of water - it will shrink and distort. So plant cell depends on both the cell wall and the vacuole to maintain its shape.)

Hi,

Just saw my sister's SA2 Paper. Interestingly, there is a question involving cell wall given an animal cell and a plant cell immersed in 2 different liquid. In one, animal cell disappears and in the other the animal cell swells.

Answer

Cell wall gives the plant a regular shape -- wrong answer.

Cell wall controls the liquid entering the plant cell -- correct answer.

[atutor2001]

Tang:

Hi,

Just saw my sister's SA2 Paper. Interestingly, there is a question involving cell wall given an animal cell and a plant cell immersed in 2 different liquid. In one, animal cell disappears and in the other the animal cell swells.

Answer

Cell wall gives the plant a regular shape -- wrong answer.

Cell wall controls the liquid entering the plant cell -- correct answer.

Hi Tang
Thanks for sharing.

I have edited my earlier post because I think the school's answer is correct because it is with reference to the experiment conducted.

The experiment did not show that cell wall gives a regular shape but it shows cell wall protect the cell from the surrounding liquid. However, the school very very dirty ... instead of using \"protect\", they use \"control\" to confuse the students. Rightfully both answers cannot. Should use \"prevent\" more accurate because \"control\" carries deeper meaning.

[Joy]

Hi Autor2001,

I just got the reply from \"Boss \" of the teacher.

Reply was :
The structure can be rigid, but not the shape which should only be fixed.

I also asked what is the right answer for PSLE.

The reply was :

strictness in PSLE marking is an unknown year-on-year, what the school would do is teach pupils the most accurate responses to such questions. Thus, by being strict at the school level, it aims to prepare every pupil well for PSLE and beyond, where science at higher levels require even more specific terminology.

Just to share.

atutor2001:

Below are just my views on the proper key words to use and the reasons :

Definitions

1. Plant cells have a regular shape. (instead of \"fixed shape\" because the shape of different parts of a plant can be different. On the other hand \"regular\" means the shape can form a pattern - which is true for all plant cells)

2. Plant cells have rigid cell wall. (instead of \"fixed\" because \"rigid\" highlights the main characteristic of cell wall, which is \"stiff\" i.e. giving it strength to support and act as \"skeleton\" for the plant. On the other hand, \"fixed\" is too general)

Functions of Cell Walls

1. To protect the cell.

2. To support the cell so as to give it / maintain a regular shape. (instead of \"fixed the shape of the cell\" because the shape of a plant cell can change a little if the vacuole is deprived of water - it will shrink and distort. So plant cell depends on both the cell wall and the vacuole to maintain its shape.)

[atutor2001]

Joy:

Hi Autor2001,

I just got the reply from \"Boss \" of the teacher.

Reply was :
The structure can be rigid, but not the shape which should only be fixed.

I also asked what is the right answer for PSLE.

The reply was :

strictness in PSLE marking is an unknown year-on-year, what the school would do is teach pupils the most accurate responses to such questions. Thus, by being strict at the school level, it aims to prepare every pupil well for PSLE and beyond, where science at higher levels require even more specific terminology.

Just to share.

Hi Joy

Thank you for your update.

Couldn't comment on the \"Boss\" answer because the exact answer given by your dd is not clear.

If we use \"rigid\" to describe shape, then it is not as appropriate but not definitely wrong. I am sure if I say something has a rigid shape, it means the shape will not change. You may like to google for the meaning of \"rigid shape\". This site (not authenticated : http://answers.yahoo.com/question/index?qid=20100922093703AAj7n0I) may be of interest to you. However, your earlier post mentioned, \"rigid cell wall\" - rigid here is used as adjective for the cell wall (i.e. structure), so should be fine.

I think the \"Boss\" is trying to say that since the question is asking about shape of a cell, then it is more appropriate to use \"cell wall has a fixed shape\". However, the teacher's answer of \"fixed cell wall\" under normal interpretation, can have a totally different meaning from \"cell wall has a fixed shape\" and is therefore, not acceptable

I would still stick to the common key words for i.e. rigid cell wall, maintain, regular shape.

Incidentally, if the school's question states that plant cell has a fixed shape, it is conceptually INACCURATE - otherwise books would have use \"fixed\" instead of \"regular\"

Anyway, not to worry. Such thing usually do not happen in PSLE because the questions are usually set by Sec or JC Teachers who are more concerned with concept instead of regurgitating blindly as in many Pr Sch

[atutor2001]

Hi, got this question that need your help. Thanks.


Lionel planted some seeds in a pot. He watered them everyday. After a few weeks, plants grew in the pot. Later, the plants died. Which of the following is/are correct conclusion(s) of this experiment?

A: Plants can grow over time.
B: Plants come from seeds.
Plants will die.
Plants need water.

(1) A only
(2) A and B
(3) A, C and D
(4) B, C and D

[I_belive]

atutor2001:

Hi, got this question that need your help. Thanks.


Lionel planted some seeds in a pot. He watered them everyday. After a few weeks, plants grew in the pot. Later, the plants died. Which of the following is/are correct conclusion(s) of this experiment?

A: Plants can grow over time.
B: Plants come from seeds.
Plants will die.
Plants need water.

(1) A only
(2) A and B
(3) A, C and D
(4) B, C and D

Hi,
I would like to know the answer too. I guess (3) is correct.