Q&A - PSLE Science

[youngtay]

Mr Tianzhu


Thanks

[atutor2001]

kenobi:

Transport system in plants involve only water and food, so the phrase \"returned to leaves\" is not appropriate. All parts of plants carry out respiration, hence it's not solely \"returned to leaves\".

Again, transport system in plants do not involve transport of oxygen. Similarly, all parts of plants carry out respiration, so they do not draw their oxygen from leaves.

Hi Kenobi

You have given the best explanation. Unfortunately, many Pr school kids think that respiration (like photosynthesis) is carried out by the leaves only.

Regards

[Tang]

Tang:

Vanilla Cake:

Compare the following differences between the respiratory and circulatory system in plants and in human beings. Which of them is wrong?


Option 1
Plant: Exchange of gases takes place in the leaves
Human: Exchange of gases takes place in the lungs

Option 2
Plant: Oxygen is pumped to all parts of the plant
Human: Oxygen is pumped to all parts of the body

Option 3
Plant: Carbon dioxide is not returned to leaves
Human: Carbon dioxide is returned to the lungs.

Option 4
Plant: There is no blood to carry food around the plant
Human: Blood carries food around the body

Answer given is option (2).
Is this correct?
Option (1) and option (4) are obviously correct.
Pls help to explain why option (2) is chosen instead of option (3) for this question.
TIA for your time and effort.

Hi,

I personally think option (3) is the correct answer.


Respiration is the conversion of food to energy. For this process to take place, oxygen is used up and carbon dioxide is produced.


Exchange of gases takes place at the leaves through stomata. So oxygen needs to be pump from the leaves to all parts of the plant and carbon dioxide to the leaves to be removed. The former shows that option (2) is correct while the latter shows that option (3) is wrong, hence the correct answer - option (3).

Hi,

My revised answer is option (2) as there is no pump in plants.


I was looking through my Biology textbook, it somehow states that \"Since the amount of carbon dioxide produced during tissue respiration is not sufficient for food-making, more carbon dioxide has to diffuse from the leaf from the outside atmosphere.\"


Since Primary School, I have been puzzled by \"breathing roots\". Why do roots have to breathe when exchange of gases takes place mainly at the leaves through the stomata.

From textbook,

\"Roots require oxygen for tissue respiration. It is obtained from the soil water as dissolved oxygen which diffuses into the root hairs and inwards to the inner cells of the root.\"

\"Light energy is absorbed by the chlorophyll and then converted into chemical energy. Light energy is also required to split the water molecules into oxygen and hydrogen, i.e. photolysis of water. Note: Not all the oxygen is derived from water.
The hydrogen produced is then used to reduce carbon dioxide to carbohydrate (glucose).\"

[meimeitan]

Hi!


Ada grouped the objects in the following way:

Group A Group B
silk blouse steel bar
glass fish tank car tyres
coloured plastic bag paper plate

What property of the objects has Ada used to classify them into Groups A and B?

Thanks.

[meimeitan]

Hi!


Sorry for the messy typing!

Group A
silk blouse
glass fish tank
coloured plastic bag


Group B
steel bar
car typres
paper plate


thanks.

[tianzhu]

meimeitan:

Ada grouped the objects in the following way:

Group A Group B
silk blouse steel bar
glass fish tank car tyres
coloured plastic bag paper plate

What property of the objects has Ada used to classify them into Groups A and B?

Hi meimeitan

The closest classification I can think of is degree of transparency to light.

Best wishes

[meimeitan]

Hi!


Thanks for your help. Another question is:

Which part of the aquatic plant allow it to float?

Thanks.

[tianzhu]

meimeitan:

Which part of the aquatic plant allow it to float?

Hi

This is a general question.
Is it the actual question or a summary from another question?

I guess the answer depends on the species or types of floating plants.

For water hyacinth, air spaces in leaf stalk help to keep the plant afloat.

Best wishes

[meimeitan]

Hi! TianZhu


Thanks for your smart guessing. Yes, it is water hyacinth. Thanks for your help.

:lol:

[tianzhu]

meimeitan:

Thanks for your smart guessing.

Hi

You're welcome.

Hope my guess for TOTO can be so accurate as well.

Best wishes