Q&A - PSLE Science

[starlight1968sg]

suiyuan:

Please help to explain.

I thought radishes and carrots reproduce from seeds.

Have you seen radish or carrot seeds?
These plants reproduce by a method called vegetative propagation.
Others such plants include ginger, potato, onion etc.

I don't really know how exactly they reproduce in this manner because reproduction needs a male reproductive cell and a female reproductive cell.

Maybe a Science teacher can help to elaborate more.

[James Ang]

suiyuan:

James Ang:

[quote=\"parentof3\"]I have a question.


Why do farmers cut off the leaves of the radish before selling them?

Thanks

The food stored in the radish may be utilised by the radish to grow into a young plant and the radish will shrink in size.

Hi

The food stored in the radish may be utilised by the radish to grow into a young plant

Please help to explain.
I thought radishes and carrots reproduce from seeds.[/quote]Carrot is an underground root and reproduces by the plant part which is underground root, meaning that you can plant a carrot with leaves and it will grow into a new plant. Other plants reproduce by plant parts are;

underground root; turnip, sweet potato, etc
underground stem; potato, ginger, onion etc
leaf: begonia, etc
suckers/shoot; banana, pineapple

[starlight1968sg]

James Ang:

Carrot is an underground root and reproduces by the plant part which is underground root, meaning that you can plant a carrot with leaves and it will grow into a new plant. Other plants reproduce by plant parts are;


underground root; turnip, sweet potato, etc
underground stem; potato, ginger, onion etc
leaf: begonia, etc
suckers/shoot; banana, pineapple

Thanks for sharing.
Does this reproduction involve a male reproductive cell and a female reproductive cell?

[tianzhu]

Hi


I am quite confused by the issue of how carrots reproduce.

On pg 133 of PSLE Science Revision Guide(Marshall Cavendish First edition), it states that carrots reproduce from seeds. For 2010 PSLE students who are having the latest edition, please help to check.

Also on the same page, it states that there are three methods classified under Reproduction from Plant Parts. They are Underground Stem, Suckers and Leaf. Reproduction from Underground Root is not included.

For the benefits of current PSLE students, we hope to hear comments from science teachers.

http://www.5min.com/Video/How-to-Grow-Carrots-59797292

Best wishes

[tianzhu]

parentof3:

I have a question.


Why do farmers cut off the leaves of the radish before selling them?

Thanks

Hi

Under the primary science syllabus, I would be inclined to answer that the radish leaves cause moisture and nutrient loss during storage. That’s why they are removed.

Best wishes

[James Ang]

tianzhu:

Hi


I am quite confused by the issue of how carrots reproduce.

On pg 133 of PSLE Science Revision Guide(Marshall Cavendish First edition), it states that carrots reproduce from seeds. For 2010 PSLE students who are having the latest edition, please help to check.

Also on the same page, it states that there are three methods classified under Reproduction from Plant Parts. They are Underground Stem, Suckers and Leaf. Reproduction from Underground Root is not included.

For the benefits of current PSLE students, we hope to hear comments from science teachers.

http://www.5min.com/Video/How-to-Grow-Carrots-59797292

Best wishes

Page 62, Mini Science Encyclopedia 5th Edition by EPB PanPacific;

Common examples of plants reproduced by vegetative propagation
(a) Roots (e.g. sweet potato, carrot)
The roots of the sweet potato and carrot store food and can also grow into new plants.
\"Diagram of sweet potato under the soil, growing a young plant\"

[P5G]

Please help.


Q6: When water is heated to 100 degree C, bubbles can be seen rising through the water. What do these bubbles contain?

(1) Hot water vapour
(2) Hot water droplets
(3) Air dissolved in the water
(4) Only oxygen is released from the hot water

Worksheet's answer is (3) and my answer is (1).
Should the bubbles be hot water vapour or air dissolved in the water? How do I decide which should be the answer? What are the key factors?


Q21: Which of the following statements about yoghurt making are true? You may refer to the link for the picture given:
http://www.orlesson.org/orp/09Sc/2009-Sc-CA1-MGS.pdf

(A): Bacteria are added
(B): Fermentation of milk takes place
(C): Oxygen is needed
(D): Yeast cells are added

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

Worksheet's answer is (1) and my answer is (3).
Please advise if oxygen is needed ?

Q43b) Name the two stages that the butterfly can be harmful to plants.
c) Describe how this is so.

Worksheet's answer b) Larva and Adult
c) They feed actively on the leaves leaving the plant with few or no leaves to make food for itself.

Is it true that adult butterfly feeds actively on leaves? I thought butterfly feeds on sap and nectar. Any comments?

TIA.

[tianzhu]

Hi


For Q6, your answer is correct. It is water vapour. A similar type of question has been discussed earlier in this thread.

For Q21, the WS’s answer is correct. Fermentation is anaerobic which means no oxygen is required.

As for Q43b, at the larval stage, caterpillars eat leaves. Therefore, they are harmful to plants.

http://www.flmnh.ufl.edu/butterflies/qanda.htm
One interesting find from this site is that some species vary their nectar diet to include rotting fruit, pollen, excrement and carrion.Pollens are carried by the wind or insects to cross pollinate other same type of plants for reproduction. If large quantities of pollen grains are consumed by adult butterflies, it’ll reduce the chances of pollination and affect the continuity/survival of plants in the long run. I hope I am leading you to the right direction and suggest that you check with your science teacher and let us know the answer.

Best wishes

[P5G]

tianzhu:

Hi


For Q6, your answer is correct. It is water vapour. A similar type of question has been discussed earlier in this thread.

For Q21, the WS’s answer is correct. Fermentation is anaerobic which means no oxygen is required.

As for Q43b, at the larval stage, caterpillars eat leaves. Therefore, they are harmful to plants.

http://www.flmnh.ufl.edu/butterflies/qanda.htm
One interesting find from this site is that some species vary their nectar diet to include rotting fruit, pollen, excrement and carrion.Pollens are carried by the wind or insects to cross pollinate other same type of plants for reproduction. If large quantities of pollen grains are consumed by adult butterflies, it’ll reduce the chances of pollination and affect the continuity/survival of plants in the long run. I hope I am leading you to the right direction and suggest that you check with your science teacher and let us know the answer.

Best wishes

Thanks Mr Tianzhu.

So answer for

43c) Larva feed actively on leaves leaving no leaf or few leaves for the plant to make food.
Adult butterfly may feed on pollen leaving no pollen grain or few pollen grains for pollination.

[James Ang]

P5G:

Please help.


Q6: When water is heated to 100 degree C, bubbles can be seen rising through the water. What do these bubbles contain?

(1) Hot water vapour
(2) Hot water droplets
(3) Air dissolved in the water
(4) Only oxygen is released from the hot water

Worksheet's answer is (3) and my answer is (1).
Should the bubbles be hot water vapour or air dissolved in the water? How do I decide which should be the answer? What are the key factors?



TIA.

I reasoned that the correct answer is (3) and not (1) for the below reasons;

1. Water vapour escape from the surface of the water rather than from the bottom of the container. (kinetic particle theory - where the active particles leave the surface of the liquid and become gas, leaving the remaining particles to have less average energy per particle)
2. Water contains dissolved air which is necessary for the survival of living things that live in water. Boiling will expel the dissolved air from the water. That's why water animals cannot live in boiled water that has cooled down as the water does not contain dissolved oxygen.

I am sure the above reasons are convincing and scientific for you.