PSLE Booklet Life Open-Ended Part2

Some of the water will be used for photosynthesis The excess water will be given off as water vapour.

The water moves upwards in one direction in plants from the roots to the leaves. However the blood circulates in the human body through the lungs, heart and other parts of the body.

It is the distance between the plant and the torch.

The worm give out carbon dioxide when they respire. Hence the rate of photosynthesis increased with more carbon dioxide.

The plants will not photosynthesize in the absence of light. Hence there will be insufficient oxygen for the worms to survive on as it needs to compete for it with the plants.

As the temperature increases the percentage of females hatched decreases.

During global warming the earths temperature increases. As the number of females hatched decreases there will be less young reproduced soon leading to extinction.

During respiration carbon dioxide is produced. The carbon dioxide is absorbed by a substance releasing some space in the test tube. The drop of ink moves in to take up the space released.

Nitrogen

As Bird P pushes the eggs of Bird Q out of the nest, It damages the eggs and decreases the number of young hatching.

It enables the young of Bird P to find food first to survive.

By keeping silent it prevents the Mother Bird of Q from identifying that it is not its young. This way it is well taken care of until it is able to fly off.

23

Chloroplast

23

It controls all activities of the cell which includes repairing the damaged parts of the cell.

A. As it has more exposed surface area, it traps more heat causing the water to boil first.

As the lizard runs on two legs the exposed surface area in contact with the ground is lesser than the snakes. Hence it does not feel that much heat.

As the Lizard runs on two legs it experiences lesser friction between itself and the sand than the snake. Hence it is able to move faster reducing the amount of heat it feels.

13. Plant P and Insect Q depend on each other as shown in the diagram below.1. How does Plant P and Insect Q benefit from this relationship? (1)

1. Benefit for Plant P: Insect Q helps to pollinate the flower of Plant P which helps to increase its population.

(ii) Benefit for Insect Q: Insect Q obtains food (nectar) from the flower of Plant P to help it to survive.

13. Plant P and Insect Q depend on each other as shown in the diagram below.1. Plant P and Insect Q are parts of a food chain. What roles does Plant P

play in the food chain? (1)

(b) Plant P is the producer of the food chain.

PSLE Examination Questions Years 2006-2010 Science

15. Suzie carried out an experiment to study the decomposition of dead leaves. She placed dead leaves and some damp soil in a bin as shown below. She was advised not to add water to the bin.

After a few months, the dead leaves were decomposed into a damp black substance which could be used as fertiliser.Suggest two things that Suzie could do to make the dead leaves decompose faster. Give a reason for each of your answers. (4)


Answer:(a)(i) Suggestion: She could poke more holes in the lid.(ii) Reason: The damp soil contains decomposers which are living things. Decomposers need oxygen in order to carry out respiration.(b)(i) Suggestion: She could put a few earthworms in the damp soil.(ii) Reason: Earthworms can break down the dead leaves into smaller pieces. The decomposers can then break down the leaves into simpler substances faster.


7(a) Johns mother put some leafy vegetables in a clear plastic bag and sealed it.

After some time, John observed that water droplets were formed on the inside of the plastic bag.Give a reason for the formation of the water droplets. (1)

Answer: The leaves of the vegetables contain many stomata.Water vapour moves out of the leaves through the stomata and condenses on the cooler surface of the plastic bag, hence forming water droplets.


(b) John was lost in a jungle and wanted to have some water to drink. He could not find a river. The plants and fruits in the jungle could not be eaten.Suggest what he could do to get some water to drink if he had the following things only:

Plastic sheet Newspapers

He need not use all of the above things.

Towel String

Answer: John could use a plastic sheet to wrap a leafy branch of a tree. Then, he should tie the plastic sheet firmly to the branch using the string.


3. Annie studied the life cycle of an insect X. She recorded the number of days for each of its life cycle. Her results are shown in the graph below. However, she did not present the stages of the life cycle in the correct order.

1.Write down the stages of the life cycle in the correct order. (1)

egg

(b) Based on Annies results, how many days does it take for insect X to become an adult after the egg has hatched? (1)

larva pupa adult

Answer: 24 days


(c) Insect X has wings. It spends certain stages of its life cycle in the water.Name all the stages spent in water and give a reason for your answer. (2)

1. Stages spent in water:

(ii) Reason:


Answer: Egg, larval and pupa stages

Answer: The egg is laid in water. It develops into a larva and then into a pupa in the water and has structural adaptations to stay in water. The adult insect X has wings. It can leave the water surface and fly away.


Answer: Very big ears provide a larger surface area for elephant A to lose heat faster.

6. Elephants live in hot places and need to lose heat through their ears.(a) Elephant A lives in an open grassy area and has very big ears. Give a reason why very big ears could be an advantage for elephant A? (1)


(b) Elephant B lives in a dense forest and has smaller ears than elephant A. Give a reason why very big ears could be a disadvantage for elephant B? (1)Answer: The dense forest is cooler than the open grassy area. Very big ears conduct heat faster away and could result in elephant B losing too much heat.


Devi then counted the number of butterflies that visited the model flowers over 3 hours. The results were recorded in the table below.

257White71115Yellow158Red10 11am9 10am8 9am

Number of butterflies visiting the flowerColour of flower

(a) Based on Devis results, which colour did most of the butterflies prefer? (1)

Answer: Most of the butterflies prefer yellow.


(b) Siew Cheng wanted to find out the relationship between the size of the flowers and the number of butterflies visiting the flowers.What changes to Devis experiment should Siew Cheng make? (2)

Answer: Siew Cheng should make three yellow flowers of different sizes. Then, she should put 10 drops of the same sweetened water in the centre of each flower and place them in the open field. She should then count the number of butterflies that visited the flowers over 3 hours.

PSLE Booklet Life Open-Ended Part2

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Transcript of PSLE Booklet Life Open-Ended Part2