The roots of these plants are absorbing water.
Plant Transport, Respiratory and Circulatory Systems
How plants move water and food, and how our lungs, heart and blood vessels move oxygen and carbon dioxide around the body. Read a little, then try it yourself. Your progress is saved on this device.
Hmmm... Don't the leaves need water too?
That's right! I think leaves and other plant parts need water too.
So how do other plant parts get water?
Think about itWhere does a leaf at the very top of a plant get its water from, if only the roots are in the water?
Something must carry the water up. Keep reading!Like other living things, plants need water, food and air to survive.
We will learn how water and food are transported to the different parts of a plant.
What I Am Learning
- Why do plants have a transport system?
- How are water and food transported in plants?
- What happens if parts of the plant transport system are removed?
Part 1 · Textbook pp. 62–63
Why do plants have a transport system?
💻 Let's Inquire
- AB: Activity 3.1
Water and mineral salts are absorbed by the roots of plants. However, other parts of a plant, such as the stem and the leaves, also need water and mineral salts for the plant to survive. How do water and mineral salts get from the roots to other parts of the plant?
Similarly, food made in the leaves is needed by the other parts of the plant for the plant to survive. How does food get from the leaves to other parts of the plant?
Plants have a transport system to carry substances to different parts.
🌿 Leaves
Leaves trap light to make food.
🌱 Roots
Roots absorb water and mineral salts.
In flowering plants, do the flowers and fruits also need water, mineral salts and food?
Substances such as water, mineral salts and food are transported to different parts of a plant through a transport system.
Answer the quick check to finish this part.
Part 2 · Textbook pp. 64–69
How are water and food transported in plants?
In the plant transport system, there are two types of tubes that transport substances. These are the water-carrying tubes and the food-carrying tubes.
🧩 Let's Connect
In the topic of Plant System, you have learnt that the stem of a plant transports food, water and mineral salts to all parts of the plant.
I observe many 'circles' in the cross-section of the celery stalk.
What are these 'circles'?
💡 I'm Inspired
Scientists often share knowledge and build on one another's findings to improve their explanations. This is no different in the discovery of the water-carrying tubes!
1675
Marcello Malpighi
He was the first scientist to observe and describe water-carrying tubes.
1727
Stephen Hales
These scientists tapped on Malpighi's findings and discovered the function of the water-carrying tubes.
1875
Julius von Sachs
These scientists tapped on Malpighi's findings and discovered the function of the water-carrying tubes.
Presence of water-carrying tubes
Water and mineral salts are absorbed by the roots of a plant. Water and mineral salts are then transported by the water-carrying tubes from the roots to the stem and then to all parts of the plant.
💻 Let's Inquire
- AB: Activity 3.2
🧩 Let's Connect
In the topic of Photosynthesis, you will learn that water is needed for plants to make food.
Presence of food-carrying tubes
Food is made in the leaves.
Food is then transported by the food-carrying tubes from the leaves to the stem and then to all parts of the plant.
💻 Let's Inquire
- AB: Activity 3.3
- SLS: Plant Transport System
ChenWhat can we observe about the water-carrying and food-carrying tubes in this plant?
Just like Chen, scientists often ask questions to make sense of what they observe around them. To find answers to their questions, scientists design investigations.
🧪 Let's Think and Do · Designing investigations
When designing an investigation, scientists first think about the aim of the investigation. This is usually related to the question that they have posed.
With the aim, scientists then plan the types of variables and steps in their investigation.
Look! These two plants are of the same type but with different numbers of leaves.
Hmmm... Do you think that the number of leaves can affect how quickly water is absorbed by plants?
What affects how quickly water is absorbed by plants?
Then the aim of our investigation is...
...to find out if the number of leaves affects how quickly water is absorbed!
Now that we have an aim for our investigation, let's think about the variable that we can change, the variables that we need to keep the same and the variable that we can measure.
That's right! Maybe we can use the same type of plant, but with different numbers of leaves.
Water and mineral salts are transported by water-carrying tubes from the roots to all parts of a plant.
Food is transported by food-carrying tubes from the leaves to all parts of a plant.
💻 Let's Inquire
- AB: Activity 3.4
Answer the quick check to finish this part.
Part 3 · Textbook pp. 69–70
What happens if parts of the plant transport system are removed?
When a cut is made around a stem to remove the food-carrying tubes, food made by the leaves cannot be transported to the parts of the plant below the cut. Excess food will be stored at part X of the stem, as shown below, causing it to swell.
💻 Let's Inquire
- AB: Activity 3.5
🌏 Science Around Us
In some fruit trees such as the nectarine, farmers remove a ring of bark containing food-carrying tubes. This will help to produce fruits of better quality, as more food is transported to the fruits instead of to the other parts of the plant.
part where food-carrying tubes have been removed
When a deeper cut is made around the stem, both the food-carrying tubes and the water-carrying tubes are removed. The food from the leaves as well as the water and mineral salts from the roots will not be transported to other parts of the plant. Over time, the plant will die.
When parts of the plant transport system are removed, the growth of the plant is affected.
Answer the quick check to finish this part.
I wonder why I feel so breathless after running.
I am so breathless too! What is happening to us?
Have you ever felt breathless like Ali, Belle, Chen and Devi after a run? Why do you think you tend to breathe faster and more deeply after running?
What I Am Learning
- What is air made up of?
- How does gaseous exchange take place in the body?
- How are oxygen and carbon dioxide transported in the body?
- How do systems work together for the survival of living things?
Part 4 · Textbook pp. 76–77
What is air made up of?
💻 Let's Inquire
- AB: Activity 4.1
Air is made up of gases
Air is all around us. We cannot see air, but we can feel the effects of moving air (wind). For example, when the wind blows, you can see leaves on the ground being lifted up.
🌏 Science Around Us
A weather forecast tells us ahead of time whether it is likely to rain and how warm it would be over the day. This allows us to plan our activities. Besides stating the temperature, wind speed and possibility of rain, a weather forecast also reports the humidity level.
Humidity is a measure of the amount of water vapour in the air. When there is more water vapour in the air, the weather is more humid.
Air contains gases such as oxygen, carbon dioxide, nitrogen and water vapour. We breathe in all these gases. We also breathe out all the same gases, but in different amounts.
Living things need the oxygen in air to survive. When living things breathe in air, they also take in oxygen.
Water vapour and carbon dioxide in the air trap some heat from the Sun to keep the Earth warm so that it is liveable. Carbon dioxide is used by plants to make food. Nitrogen in air can be used by some bacteria to help plants grow better.
A girl breathing
🔍 Let's Explore
Silica gel is a substance that removes water vapour from the surrounding air. It is often used to keep things dry. This helps prevent mould from growing and allows some types of food to be preserved for a longer time.
For example, food companies include silica gel when packaging some types of food, such as biscuits, to keep them fresh and crunchy. Photographers also use silica gel to keep their equipment, such as cameras and lenses, dry.
Take a look around you.
What are some ways that you see silica gel being used at home?
Some silica gel changes in colour as it removes water vapour from the surrounding air.
Do not eat silica gel, as it contains chemicals that can be harmful to your body.
Air is necessary for the survival of living things. Air is a mixture of gases.
Answer the quick check to finish this part.
Part 5 · Textbook pp. 78–80
The respiratory system — How does gaseous exchange take place in the body?
DeviHi, Chen. Is that a fitness tracker? What can it measure?
Blood Oxygen98%Done
ChenYes. It is interesting to know that the fitness tracker can measure the amount of oxygen in our blood.
DeviI wonder how oxygen enters our body.
The respiratory system is involved in the exchange of gases between our body and our surroundings.
The respiratory system includes the following parts:
- nose
- windpipe
- lungs
🧩 Let's Connect
In the topic of Human Systems, you have learnt about the parts and function of the respiratory system.
💻 Let's Inquire
- AB: Activity 4.2 (Part A)
- SLS: Human Respiratory System
How do gases enter and leave our body?
Breathing
We take in and give out air all the time. This process is called breathing. What happens when we breathe?
When we breathe in, air enters our body through our nose. The air that is breathed in is called inhaled air.
As air passes through the nose, dust is trapped by the tiny hairs in the nose. This filtered air is also warmed and moistened.
From the nose, the air enters the windpipe.
From the windpipe, the air enters the lungs and fills the air sacs. Gaseous exchange happens in the lungs.
Gaseous exchange occurs when oxygen in air enters the blood in the lungs, and carbon dioxide is removed from the blood.
During gaseous exchange, all the gases in air enter the air sacs at the same time. It is not only oxygen that enters the air sacs and it is not only carbon dioxide that leaves the air sacs.
Oxygen moves from the air sacs into the blood, while carbon dioxide moves from the blood to the air sacs.
Air sacs
When we breathe out, the air leaves the lungs, passes through the windpipe and exits through the nose. The air that is breathed out is called exhaled air.
💻 Let's Inquire
- AB: Activity 4.2 (Part B)
- SLS: Oxygen in the Air
Answer the quick check to finish this part.
Part 6 · Textbook pp. 81–82
🧪 Let's Think and Do · Understanding data representation using pie charts
TeacherLet's find out the difference between the composition of inhaled and exhaled air.
There are many ways by which we can represent information. We can use charts, graphs and pictures to help us present patterns and relationships in data.
For example, pie charts are a useful way to show information visually and help people understand complex information easily. A pie chart is a type of chart that uses a circle (or a pie) that has been divided into smaller parts.
In the pie charts below, we can see that there is more nitrogen in air than other gases.
ChenNow, let's compare the two pie charts carefully.
The amount of nitrogen remains the same at 78% in inhaled and exhaled air.
There is a greater amount of oxygen in inhaled air (21%) than in exhaled air (16%).
There is a smaller amount of carbon dioxide in inhaled air (0.04%) than in exhaled air (4.4%).
DeviWhat other ways can we represent the different amounts of gases in inhaled and exhaled air?
🌏 Science Around Us
Do you know of anyone who has asthma? Some of us may have experienced asthma when we were younger.
During an asthma attack, a person may experience symptoms such as shortness of breath, chest tightness and wheezing. The symptoms of asthma are caused by the narrowing of the airways due to swelling or the increased production of a slimy, sticky substance called mucus.
Narrowing of airways causing an asthma attack
Try to stay calm when you encounter someone experiencing asthma symptoms. Panic and stress can worsen these symptoms.
If the person has an inhaler, he or she should use it as prescribed by the doctor. The medicine in the inhaler helps to open the airways and reduce mucus. Air can enter the lungs more easily, which helps the person breathe.
An inhaler containing medicine is used to relieve asthma symptoms.
Answer the quick check to finish this part.
Part 7 · Textbook pp. 83–86
Do all living things take in oxygen and give out carbon dioxide in the same way?
💻 Let's Inquire
- AB: Activity 4.3
- SLS: Gaseous Exchange in Plants and Fish
Look at the plant and the fish. How do you think the plant and the fish take in oxygen and give out carbon dioxide?
Plant
Fish
Exchange of gases in plants
Plants, like all other living things, need air to survive. They take in oxygen and give out carbon dioxide through tiny openings found mostly on leaves.
When plants make food, they also take in carbon dioxide from the surrounding air and give out oxygen.
🧩 Let's Connect
In the topic of Photosynthesis, you will learn more about how plants make food.
🔍 Let's Explore
The tiny openings found on leaves also allow other gases such as water vapour to move into and out of a plant.
The tiny openings can also change in size according to different environmental conditions. How does the change in the size of the tiny openings affect the rate of gaseous exchange?
The tiny opening is smaller. · The tiny opening is larger.
Exchange of gases in fish
Fish live in water and take in oxygen that is dissolved in the water.
The oxygen-rich water enters the body of a fish through its mouth and passes through its gills.
At the gills, oxygen moves into the blood and is transported to all parts of the body. Carbon dioxide from the body then moves to the blood at the gills.
As water flows over the gills and leaves the body of the fish, carbon dioxide is removed as well.
Comparing exchange of gases in plants, fish and humans
Plants, fish and humans use different parts to take in oxygen and give out carbon dioxide. Plants use the tiny openings on their leaves for gaseous exchange, fish use their gills, while humans use their lungs.
🌏 Science Around Us
Have you ever wondered why people check the gills of a fish before buying the fish?
When a fish is freshly caught, the gills are bright red. The bright red colour will slowly darken over time partly due to interactions between blood and oxygen in the air. As such, the brighter the colour of the gills, the fresher the fish. That is why people who want to buy fresh fish lift the gill cover first to check whether the gills are bright red.
Checking the freshness of fish by examining the colour of the gills
Different parts of the respiratory system have different functions for gaseous exchange to take place.
Plants, fish and humans have different ways of taking in oxygen and giving out carbon dioxide.
Answer the quick check to finish this part.
Part 8 · Textbook pp. 87–92
The circulatory system — How are oxygen and carbon dioxide transported in the body?
ChenThe blood oxygen level tells us how much oxygen is in our body.
DeviThen what about this? What does this number mean?
Heart Rate❤ 83Tap to measure
ChenIt's your heart rate. Look at the icon of the heart!
ChenDo you know how the oxygen from our lungs reaches our toes? Our lungs and toes are quite far apart.
DeviI think there must be a transport system in our body to move the oxygen around.
The human body is made up of different parts. As different parts of the body may be far from one another, a transport system is needed to move substances such as oxygen around the body.
💻 Let's Inquire
- AB: Activity 4.4
- SLS: Human Circulatory System
The transport system in humans is known as the circulatory system. It carries substances such as digested food and oxygen to different parts of the body. It also carries waste materials away from different parts of the body for removal.
The circulatory system includes the following parts:
- heart
- blood vessels carrying blood
🧩 Let's Connect
In the topic of Human Systems, you have learnt about the parts and function of the circulatory system.
Look at the diagram of the human circulatory system above. You can see that blood vessels are found all over the body. These blood vessels are like rail tracks linking different parts of the body so that substances can be transported. Blood flows inside the blood vessels like trains moving on tracks. Blood carries substances such as water, oxygen, carbon dioxide and digested food.
Major blood vessels linked to the heart allow substances to enter and leave the heart.
The heart is a muscle that pumps blood to different parts of the body. As it pumps, it provides a force that pushes blood through blood vessels.
The heart pumps all the time - even when we are sleeping! This continuous pumping keeps blood flowing throughout our body so that we stay alive.
A model of a human heart
🔍 Let's Explore
How does the heart pump blood to different parts of the body?
The heart pumps by contracting and relaxing.
When the heart pumps, blood is pushed from the heart to different parts of the body through the blood vessels. This causes an increase in the pressure in your blood vessels and creates a rhythm that you can feel. This rhythm is called a pulse.
You can feel your own pulse by gently placing your fingers on your wrist or on the side of your neck.
Possible locations to feel a pulse
Do you notice that your pulse has a steady beat? The number of times your heart beats in a minute is your heart rate.
💡 I'm Inspired
The first stethoscope was invented by a doctor, René Théophile Hyacinthe Laënnec, in 1816. It was a short, wooden tube with an earpiece and a hole. Laënnec often used it to listen to the various sounds made by the lungs and the hearts of his patients.
The first stethoscope · Laënnec using the first stethoscope on a patient
At first, many doctors did not appreciate the use of the stethoscope. They felt that it was best to listen to sounds made by the lungs and the heart using their own ears instead. However, that did not stop Laënnec. He continued to use it to diagnose diseases and diligently recorded his observations. He then shared his methods and findings, many of which are still relevant in the field of medicine today.
The design of stethoscopes has continued to be improved over the years. This has allowed medical professionals such as doctors to listen to the sounds of the heart, the lungs and the flow of blood more precisely.
The modern stethoscope
Answer the quick check to finish this part.
Part 9 · Textbook p. 93
Do plants have the same transport system as humans?
AliI wonder how substances are transported in plants.
💻 Let's Inquire
- AB: Activity 4.5
Just like humans, plants have a transport system. The transport systems in both plants and humans carry food and water. Besides food and water, the human transport system also carries oxygen and carbon dioxide.
The way the human body transports food and water differs from plants. The human body transports food and water together in the blood through the blood vessels. However, plants transport these substances in separate food-carrying and water-carrying tubes.
🧩 Let's Connect
In the topic of Plant Transport System, you have learnt about the functions of food-carrying and water-carrying tubes.
| Polymath summary | 🌿 Plant transport system | 🧒 Human circulatory system |
|---|---|---|
| Carries | Food, water and mineral salts | Food (digested food) and water, and also oxygen and carbon dioxide |
| Carried in | Separate tubes: water-carrying tubes and food-carrying tubes | Blood, together, through the blood vessels |
| Takes in oxygen and gives out carbon dioxide through | Tiny openings found mostly on leaves | The lungs (the respiratory system) |
Different parts of the circulatory system have different functions to transport substances in the body.
Plants and humans have different ways of transporting substances.
Answer the quick check to finish this part.
Part 10 · Textbook pp. 94–97
How do systems work together for the survival of living things?
💻 Let's Inquire
- AB: Activity 4.6
- SLS: Integration of Human Systems
DeviMy heart rate has gone up!
ChenMine too! I'm breathing faster too!
The different systems in our body work together to ensure our survival.
If one system does not function well, our body may become sick.
🧩 Let's Connect
In the topic of Human Systems, you have learnt about parts and functions of the muscular, skeletal and digestive systems.
Before a vigorous activity such as a run, Devi's and Chen's heart rates were at the resting level. The resting level refers to the heart beating at a slower pace when they are less active, such as when they are sitting or lying in bed.
When resting, the respiratory system and the circulatory system work together to ensure that substances such as oxygen and digested food are transported to different parts of the body.
After their run, the breathing rates and heart rates of Devi and Chen increased.
DeviMy heart rate is 72 beats per minute.
DeviMy heart rate is 98 beats per minute now!
ChenWow, it has increased! How about your breathing rate?
When Devi and Chen run, more oxygen and digested food need to be delivered to their muscles to enable them to run. Besides the muscular and skeletal systems, the digestive, respiratory and circulatory systems also need to work together.
The skeletal system and the muscular system help Devi and Chen move. When muscles work, more carbon dioxide is produced and this needs to be removed at a faster rate as well.
To take in more oxygen and give out more carbon dioxide from the body, Devi and Chen breathe faster. This increases their breathing rates.
To transport more oxygen from the lungs to the muscles and more carbon dioxide from the muscles to the lungs, the heart needs to pump faster. The heart also pumps faster to provide more digested food for energy. As such, Devi's and Chen's heart rates also increase.
The digestive system also needs to work faster to digest food so that it can also be transported to the muscles.
🔍 Let's Explore
When you are excited or when you are exercising, your heart rate tends to increase. Your heart pumps faster to deliver more oxygen to your muscles and to remove carbon dioxide.
Investigate how your daily activities and experiences can affect your heart rate.
Look at the pictures below. How do the breathing rates and the heart rates change for each activity? How do the digestive, respiratory and circulatory systems work together to help us carry out each activity?
Swimming · Walking · Resting · Jumping
🌏 Science Around Us
It is important for us to take good care of our respiratory and circulatory systems. One way is adopting healthy habits! This means eating right, maintaining an active lifestyle and avoiding harmful activities.
A balanced diet
Eating right reduces the chances of having harmful fatty deposits along our blood vessels. This allows for more blood to be carried by the blood vessels and for our heart to pump blood more efficiently.
An active lifestyle, including regular exercise such as jogging and swimming, can also strengthen our heart and prevent heart diseases.
Children exercising
Another way to ensure that our lungs are in good condition is to avoid harmful activities such as smoking. Such activities introduce harmful chemicals into our body and can cause illnesses.
A pair of healthy lungs · A pair of smoker's lungs
Different systems, such as the circulatory, respiratory and digestive systems, work together to help us carry out daily activities.
💻 Let's Inquire
- AB: Activity 4.7
Answer the quick check to finish this part.
Part 11 · Textbook pp. 71–73, 98–101
Let's Apply
These are the questions from the end of both chapters: four on the plant transport system and five on the human respiratory and circulatory systems. Choose or write an answer to see whether you are right and why.
Chapter 3 · Plant Transport System
Chapter 4 · The Human Respiratory and Circulatory Systems
Your score
0 / 9
Answer all nine questions.
Part 12 · Textbook pp. 74, 102–103
What I Have Learnt
Chapter 3 · Plant Transport System
- Substances such as water, mineral salts and food are transported to different parts of a plant through a transport system.
- Water and mineral salts are transported by water-carrying tubes from the roots to all parts of a plant.
Food is transported by food-carrying tubes from the leaves to all parts of a plant. - When parts of the plant transport system are removed, the growth of the plant is affected.
Chapter 4 · The Human Respiratory and Circulatory Systems
- Air is necessary for the survival of living things. Air is a mixture of gases.
- Different parts of the respiratory system have different functions for gaseous exchange to take place. Plants, fish and humans have different ways of taking in oxygen and giving out carbon dioxide.
- Different parts of the circulatory system have different functions to transport substances in the body. Plants and humans have different ways of transporting substances.
- Different systems, such as the circulatory, respiratory and digestive systems, work together to help us carry out daily activities.
Keep going!
Finish every part to complete the topic.