Q&A - PSLE Science

[cimman]

kittycat01:

Thank you very much, atutor. It's a pleasure reading your explanation. Very detailed and clear.

here's what I found while trawling the web:
http://www.tomatosphere.org/teacher-resources/teachers-guide/grades-8-10/plants-and-light.cfm

Carbon dioxide is a factor in decreasing rate of photosynthesis. While there is light, rate of respiration is lower than rate of photosynthesis, so carbon dioxide produced through respiration is insufficient for photosynthesis. Thus overall volume of carbon dioxide will steadily decline. The experiment documented in the article also has a sealed container for the plant and it has a lamp as well. Seems like a popular setup for studying rate of photosynthesis in plants.

Here is another article that talks about which wavelengths of light is more effective (ie. absorbed the most) for photosynthesis. For those who have greenhouses, blue light is the best, followed by red. Yellow is the worse.
http://fhs-bio-wiki.pbworks.com/w/page/12145771/Factors%20effecting%20the%20rate%20of%20photosynthesis
So, feed your indoor plants blue light...

[atutor2001]

Thank you cimman. The sites are very informative.

[kittycat01]

1)Is it correct to say food and water are transported to all parts of the plant? I thought so too but my child argue that the food that goes out of a leaf for example cannot travel back to itself or water that travel out of the roots cannot go back to the roots or can it?


What about a leaf producing food does it also travel to the other leaves because they already producing food themselves. so is it correct to say travel to 'all' parts of plants?

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]

kittycat01:

1)Is it correct to say food and water are transported to all parts of the plant? I thought so too but my child argue that the food that goes out of a leaf for example cannot travel back to itself or water that travel out of the roots cannot go back to the roots or can it?


What about a leaf producing food does it also travel to the other leaves because they already producing food themselves. so is it correct to say travel to 'all' parts of plants?

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?

1) It is commonly used term that \"food is transported to all parts of the plant.\" Technically, this is inaccurate because a healthy leaf that is already making food on its own, need not receive food from other parts.
However, I feel it is ok. If we really want to be 100% correct then maybe we can add : \"food is transported to all parts of the plant when needed.\"

Unlike water which can only travel upwards, food can travel in all directions. As to whether can food travel back to the leaf that make it, I think it is yes. Excess food is stored as starch in different parts of a plant. If there is a prolonged period of no light (i.e. photosynthesis stopped), the leaves will draw from this stored food. This means that the food is travelling back to the leaves.

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)

[Verysuperkiasu]

deleted

[kittycat01]

atutor2001:

1) It is commonly used term that \"food is transported to all parts of the plant.\" Technically, this is inaccurate because a healthy leaf that is already making food on its own, need not receive food from other parts.
However, I feel it is ok. If we really want to be 100% correct then maybe we can add : \"food is transported to all parts of the plant when needed.\"

Unlike water which can only travel upwards, food can travel in all directions. As to whether can food travel back to the leaf that make it, I think it is yes. Excess food is stored as starch in different parts of a plant. If there is a prolonged period of no light (i.e. photosynthesis stopped), the leaves will draw from this stored food. This means that the food is travelling back to the leaves.

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)

I guess my child is reading too much into the question. I also thought it is generally what people would say that food and water travel to all parts of the plant. It actually appears in mcq where question is asked to choose which option is correct and that is one of the options. She said because of the word 'all' she didn't pick that one. Haiz....

As for the community question, I see what you mean - that there must be interaction among the different populations. Other than frogs eating butterflies, the caterpillar is seen in the picture settling on the leaves. It is part of the pond community right? So even if the text bk or psle guide states butterfly belonging to garden, it is still considered one community in this particular picture I suppose.

Thank you, atutor for your reply.
:salute:

[pixiedust]

source: school ws


http://i1197.photobucket.com/albums/aa424/pixie_dust8/science1.jpg\">

I thought both coin and iron nail allow electricity current to pass through but I am confused by the question 'Which one...'.

Am I missing something ? What's your answer for (a) (b). Thanks.

[Chenonceau]

Here is my son’s take on it.


(1) Assuming that the coin is a non-conductor, then the circuit can NEVER be complete. Hence, neither bulb will light up.

(2) Assuming that the nail is a non-conductor, then only Bulb A will light up.

In view of the above reasoning, if there is ONLY one bulb, it has to be Bulb A. However, my son thinks that this is simply a badly phrased question. My son proposes to rephrase the question as…

Which bulb(s) would light up?

Ok… THAT is what my son thinks. Dunno if correct.

[Sun_2010]

pixiedust:

source: school ws


http://i1197.photobucket.com/albums/aa424/pixie_dust8/science1.jpg\">

I thought both coin and iron nail allow electricity current to pass through but I am confused by the question 'Which one...'.

Am I missing something ? What's your answer for (a) (b). Thanks.

You are right , both bulbs should light up.

Chen's' Ds is right the Q is not correctly phrased.

Coins and Iron both are good conductors of electricity.

Coins are made of aluminum or Copper-Nickle Allos both of which are excellant conductors of electricity.

Iron is also good conductor too - rust being the only problem.

[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) ?