Q&A - PSLE Science

[mother777]

stary:

Hi all, need explanation again.


Refer to (SCGS/Prelim/P6/2010/Booklet B/Question 40)

Samantha put up the 3 set-ups below. All the set-ups had similar plants and 250ml of water each but differnt humidity levels. She conducted the experiment for 3 days. She wanted to find out if humidity level affects the amount of water lost by the plant through its stomata.

Set-up A (Humidity: 90%)
Set-up B (Humidity: 29%)
Set-up C (Humidity: 57%)


...........

a)What......... plants through its stomata?
My answer: The higher the humidity level, the lesser the amount of water lost by the plants through its stomata.
Ans sheet: The higher the humidity level, the more the amount of water lost by the plants through its stomata.

Many thanks!

Hi Stary,

I agree with your answer too.

Just to confirm again, I searched the internet and found the below explanation:

\" Relative humidity: As the relative humidity of the air surrounding the plant rises the transpiration rate falls. It is easier for water to evaporate into dryer air than into more saturated air.\"

This is from the link below.
http://ga.water.usgs.gov/edu/watercycletranspiration.html

This link also explain other factors affecting plant transpiration.

Hope this helps (lets also wait for other KS parents to reply back too and enlighten us)

[stary]

Thanks mother777!

[Ash001]

Need help here. School answer is 4

My son answer is 1

I had asked my son to asked the teacher.
-Her explanation is diagram C is with same brightness. I am not convinced here. Look at the qns once again, the keyword is \"light up\" with \"equal brightness\"

-I dont really know the explanation on diagram D as my son didnt understand what she was saying. This diagram D confirm only the upper bulk get light up.



http://i56.tinypic.com/bdwjv8.jpg\">

[tianzhu]

Verysuperkiasu:

But I need to know :


1) option 2 says 'plants will survive longer than larger animals'. Why only larger animals?

2) Assuming food is given to the animals, then can the answer be (4) - will this constant exchange of gases between the plants and the animals be able to last for several months?

Hi Verysuperkiasu

We can apply the concepts behind the terrarium to answer your question.

Here’s a link to a write up which offers good explanation on how air is recycled in a terrarium.

http://www.ehow.com/info_8739797_do-terrariums-recycle-air.html

Going through the elimination process in the MCQ’s choices, we can immediately rule out (1) and (3).

On closer examination, (4) is also out as organisms need more than air to survive. As taught in lower primary science, living things need air, food and water to stay alive.

This leaves us with (2) which is the answer to the MCQ question.

Usually the animals and plants are carefully selected to live in an enclosed container, one doesn’t pick animals which would fight and eat other animals or cause destruction to the plants.

I guess a logical explanation is that a bigger animal(assuming non plant eater) has a bigger body and with that a bigger appetite, hence their chances of survival decreases when food becomes scarce.

As to your second question on the limit for recycled air, please refer to the last paragraph(brief history) of the article.

Hope this helps.

Best wishes

[Verysuperkiasu]

tianzhu:

I guess a logical explanation is that a bigger animal(assuming non plant eater) has a bigger body and with that a bigger appetite, hence their chances of survival decreases when food becomes scarce.

As to your second question on the limit for recycled air, please refer to the last paragraph(brief history) of the article.

Hope this helps.

Best wishes

Thanks, Tianzhu for your detailed explanation. And very informative article too....

[IMTRYINGSTUFF]

Ash001:

Need help here. School answer is 4

My son answer is 1

I had asked my son to asked the teacher.
-Her explanation is diagram C is with same brightness. I am not convinced here. Look at the qns once again, the keyword is \"light up\" with \"equal brightness\"

-I dont really know the explanation on diagram D as my son didnt understand what she was saying. This diagram D confirm only the upper bulk get light up.


http://i56.tinypic.com/1109550.jpg\">

I can't see the image. It's too small

[IMTRYINGSTUFF]

Nebbermind:

Verysuperkiasu:

Picture shows an glass aquarium with aquatic plants and some animals like fish, waterboatman and water fleas. Tank is sealed with a glass plate and whole aquarium placed in a brightly lit room the whole day.


Qn : Which of the following statements is correct about the organisms after several months?

1) All the organisms will die as there is hardly any air in the tank
2) The plants can survive longer than the larger animals in the tank
3) The animals will all die in less than a day as there is insufficient air
4) The organisms could still survive as there is a continuous supply of air.
Answer is 2)

Son's answer is 4) as there is a constant exchange of gases between the plants and animals - plants give out oxygen (during photosynthesis as the glass aquarium is placed in the light whole day) for the animals to take in and animals breathe out CO2 for the plants to take in. But my question is 'can this exchange of gases take place forever in a sealed container - is there a time limit to this? Note the question says 'after several months'.

My answer is 2). The plants will survive the longest as the conditions of the surroundings have fulfilled the necessary conditions for survival. They have oxygen from the oxygen they made from photosynthesis, food from photosynthesis and water all around them. However, the animals do not have food.

[tianzhu]

Ash001:

Need help here. School answer is 4

My son answer is 1

Hi

Please watch this video.

It helps to address your query on diagram C.

http://www.youtube.com/watch?v=jxMV0wagR8o&feature=related

Best wishes

[tianzhu]

Verysuperkiasu:

Thanks, Tianzhu for your detailed explanation. And very informative article too....

Hi

You're welcome.

Best wishes

[chrisu]

Your son's answer is right, the answer is (1) - A and B both in fact are the same, just that the battery is shifted to the left.


Diagram C, bulb will not light up and Diagram D only the top bulb will light up (as you have mentioned). Both C and D are due to the shorted path.

In fact the very top given diagram, the bulb will not light up as it's a shorted path across the battery.

Also I wonder why the need to show the very top diagram as the question is not ask to compare the same brightness as the top diagram. The question only ask same brightness for the 2 bulbs.

Seems like a number of schools are making the same mistake over and over again. Maybe MOE should stop school from setting questions that the teachers themselves are not familiar with.

Ash001:

Need help here. School answer is 4
My son answer is 1

I had asked my son to asked the teacher.
-Her explanation is diagram C is with same brightness. I am not convinced here. Look at the qns once again, the keyword is \"light up\" with \"equal brightness\"

-I dont really know the explanation on diagram D as my son didnt understand what she was saying. This diagram D confirm only the upper bulk get light up.



http://i56.tinypic.com/bdwjv8.jpg\">