Q&A - PSLE Science

[bestwishes]

Sun_2010:

pixiedust:

Thanks, Chenonceau & Sun_2010. Appreciate that.


How about this one :
http://i1197.photobucket.com/albums/aa424/pixie_dust8/sci2.jpg\">

The answer is (2) but I can't reconcile it! I thought the answer is (4) ?

Book answer is correct.
Only B2 and B3 can work . Look carefully, B4 is having a wire across it and when the switch is closed B1 will have it too.

Personnally think that this type of qn shd not be included in sch exam paper. MOE shd do something to advise 'top school' not to purposely set such tricky qns that are out of syllabus (shd be in O level sc, right?)!! Build up the strong fundamental sc concepts for primary kids is more essential, rather than having a lot of tricky qns before kids have a good understanding of basic concepts. Right?

[linden2000]

elkniwt:

Hi,


Qn: What adaptations enable the whale and dolphin to live in the water?
A: flippers
B: webbed feet
streamlined body shape
blowholes located at the top of the head

(1) A and B only
(2) B and C only
(3) C and D only
(4) A, C and D only
The answer in the answer key is (3). Why isn't it (4)? :? :?:

Hi. According to my son, flippers are for steering and changing direction and so these may not be deemed to enable them to 'live' in the water. Unlike their tail fins which they absolutely need to be able to swim.

Perhaps that is the reasoning? :?

[cimman]

linden2000:

elkniwt:

Hi,


Qn: What adaptations enable the whale and dolphin to live in the water?
A: flippers
B: webbed feet
streamlined body shape
blowholes located at the top of the head

(1) A and B only
(2) B and C only
(3) C and D only
(4) A, C and D only
The answer in the answer key is (3). Why isn't it (4)? :? :?:

Hi. According to my son, flippers are for steering and changing direction and so these may not be deemed to enable them to 'live' in the water. Unlike their tail fins which they absolutely need to be able to swim.

Perhaps that is the reasoning? :?

I think this is another one of those badly set questions. To live in the water, the whale/dolphin has to get it's food by going after it's prey. No prey, means no food, means whale/dolphin dies. To get to it's prey, both propulsion (tail fin) and steering (fin) are necessary. One can't really catch anything with just a tail fin.
Maybe the way to tackle such question, is to choose the less obvious answer, which is (3). Though (4) is the logical answer.

[atutor2001]

elkniwt:

Hi,


Qn: What adaptations enable the whale and dolphin to live in the water?
A: flippers
B: webbed feet
streamlined body shape
blowholes located at the top of the head

(1) A and B only
(2) B and C only
(3) C and D only
(4) A, C and D only
The answer in the answer key is (3). Why isn't it (4)? :? :?:

If C is part of the answer then A should also be part of the answer as both C & A enable the whale to move about in the water. (The forelimbs of whale/dolphin have evolved into flippers - an adaptation that allows enable them to swim in the water).

I think there is a mistake in the answer key. The answer should be (4)

[kitty2]

I wonder does the PSLE covers Muscular System?If yes,is it in details?


Thanks for sharing

[Just2Random]

The PSLE does cover the muscular system, but not in details. Such questions include:


What system(s) work(s) closely with the skeletal system for movement?

[kitty2]

Just2Random:

The PSLE does cover the muscular system, but not in details. Such questions include:


What system(s) work(s) closely with the skeletal system for movement?

Thanks for your reply

[Vanilla Cake]

kittycat01:

The picture in the question shows a plant in a sealed beaker of soil (only the bottom part of the plant that means the root part is sealed in the beaker). But there's some water in the sealed beaker. The whole plant is sealed in a clear container and put out in the sun. Quesion says the rate of photosynthesis is decreasing.....and is due to what? is it carbon dioxide or water. To answer the question must ask ourselves which one is used up first - carbon dioxide or water?

atutor2001:

This is a terrible question. Lets try to list down the effects of :
1. sealing the soil
2. sealing the plant
3. placing it under the sun.

1. Sealing the soil means water condensing in the outer container cannot return to the soil. Water from the soil cannot evaporate away under the sun. It also means the roots will use up the oxygen for respiration (an additional confusing factor) and will rot (an additional confusing factor).

2. Supply of carbon dioxide to the plant is limited and will be used up eventually. Sealing the plant means water vapour given out by the plant cannot escape (but also cannot return to the soil)

3. Placing the plant under the sun means light will be converted to heat inside the set-up and is trapped (greenhouse effect). Temperature inside the set-up will rise and the plant will give out more water vapour to cool down the plant. i.e. rate of transpiration will increase. However, with bright light from the sun, the rate of photosynthesis will also increase.

From the able analysis, we can see that both the rate of usage of water and carbon dioxide have increased. Therefore, to determine which is the main cause for the rate of photosynthesis to decrease, (i.e. which is used up first), the amount of water (i.e. size of the pot) and carbon dioxide available (i.e. size of the outer enclosure) will be the determining factor.

Based on my reading of the mindset of the person who set the question, I think the answer he/she wants is \"water\" because water is used for both transpiration and photosynthesis while carbon dioxide is used only for photosynthesis.

Anyway, it is a lousily set question as I can argue that the amount of water in the pot was \"so much so\" that carbon dioxide is used up first. The saddest truth is in real life, the photosynthesis will decrease not due to lack of water nor carbon dioxide. The plant will be dying because it cannot remove heat fast enough because of the intense heat inside the set-up (like the interior of a car parked under the hot sun)

PS once I bought a pot of orchid, left it in the car (under the sun) and continued shopping for less than an hour. The orchid looks fine when I reached home. I was shocked the next morning to find all the leaves had turned brown - it was just amazing.

Hi atutor2001,
Here's the question (placed under a lamp and not under the sun):

Study the set-up as shown below:
http://i41.tinypic.com/2aa0t3a.png\">
After some time, the rate of photosynthesis of the plant slowed down. This was most likely caused by a lack of ________________.

(1) water
(2) oxygen
(3) chlorophyll
(4) carbon dioxide

[Choco05]

Vanilla Cake:

kittycat01:

The picture in the question shows a plant in a sealed beaker of soil (only the bottom part of the plant that means the root part is sealed in the beaker). But there's some water in the sealed beaker. The whole plant is sealed in a clear container and put out in the sun. Quesion says the rate of photosynthesis is decreasing.....and is due to what? is it carbon dioxide or water. To answer the question must ask ourselves which one is used up first - carbon dioxide or water?

atutor2001:

This is a terrible question. Lets try to list down the effects of :
1. sealing the soil
2. sealing the plant
3. placing it under the sun.

1. Sealing the soil means water condensing in the outer container cannot return to the soil. Water from the soil cannot evaporate away under the sun. It also means the roots will use up the oxygen for respiration (an additional confusing factor) and will rot (an additional confusing factor).

2. Supply of carbon dioxide to the plant is limited and will be used up eventually. Sealing the plant means water vapour given out by the plant cannot escape (but also cannot return to the soil)

3. Placing the plant under the sun means light will be converted to heat inside the set-up and is trapped (greenhouse effect). Temperature inside the set-up will rise and the plant will give out more water vapour to cool down the plant. i.e. rate of transpiration will increase. However, with bright light from the sun, the rate of photosynthesis will also increase.

From the able analysis, we can see that both the rate of usage of water and carbon dioxide have increased. Therefore, to determine which is the main cause for the rate of photosynthesis to decrease, (i.e. which is used up first), the amount of water (i.e. size of the pot) and carbon dioxide available (i.e. size of the outer enclosure) will be the determining factor.

Based on my reading of the mindset of the person who set the question, I think the answer he/she wants is \"water\" because water is used for both transpiration and photosynthesis while carbon dioxide is used only for photosynthesis.

Anyway, it is a lousily set question as I can argue that the amount of water in the pot was \"so much so\" that carbon dioxide is used up first. The saddest truth is in real life, the photosynthesis will decrease not due to lack of water nor carbon dioxide. The plant will be dying because it cannot remove heat fast enough because of the intense heat inside the set-up (like the interior of a car parked under the hot sun)

PS once I bought a pot of orchid, left it in the car (under the sun) and continued shopping for less than an hour. The orchid looks fine when I reached home. I was shocked the next morning to find all the leaves had turned brown - it was just amazing.

Hi atutor2001,
Here's the question (placed under a lamp and not under the sun):

Study the set-up as shown below:
http://i41.tinypic.com/2aa0t3a.png\">
After some time, the rate of photosynthesis of the plant slowed down. This was most likely caused by a lack of ________________.

(1) water
(2) oxygen
(3) chlorophyll
(4) carbon dioxide

Hi i think the answer would be (4). Photosynthesis requires carbon dioxide to be carried out, and it will give out oxygen during the process. Which means the level of carbon dioxide keeps decreasing as the plant carries out photosynthesis, and since carbon dioxide is needed for photosynthesis, the rate is slowed down.

[Vanilla Cake]

kittycat01:

2) picture shows a pond with frogs outside pond and tadpoles inside pond, butterflies flying and caterpillars on the leaves of some aquatic plants (there are 3 different types of plants), fishes.


How many communities in the picture above? Some argue 2 because caterpillars & butterflies belong to garden community. But by definition of community - it means DIFFERENT populations together that means at least 2 or more right? Cater. & butt belong to 1 pop right? So if there is only 1 pop, then cannot form a community. So is it 1 or 2 comm?

atutor2001:

2) I think the most important word we need to consider for \"community\" is \"interaction\". A person standing at a pond community is not part of that community because he/she does not depend/interact on/with the other pollutions in the pond community for survival and vice versa.

With regard to the \"size/limit\" of a community, there is no set rule on the \"size/limit\" of a community. It is up to the person who is doing the study to decide. A pond in a garden can be broken into 2 communities i.e. pond & garden or it can also be considered as 1 single community. The important factor is that there must be interaction among the populations in the \"defined community.\"

Therefore, in your example, I will take it as 1 community (garden with pond community) because there is interation between frog and butterfly (frog eats butterfly/caterpillar)

The diagram below shows a habitat with some living things.
http://i40.tinypic.com/ivlb7r.png\">
Based on the diagram shown, which one of the following statements is correct?

(1) There is one community with six populations.
(2) There is one community with eight populations.
(3) There are two communities with six populations.
(4) There are two communities with eight populations.