Exam practice
Every question from the end of every unit, with hints and answers to open. After you check an answer, mark how you did, and come back to the ones you didn’t get.
15 questions
Unit 5 · Life Process
2. Fill in the blanks
The production of energy by breaking down food takes place in ……… .
Answer
respiration
Plants take in ……… during respiration.
Answer
oxygen
Transportation in unicellular animals takes place through the ……… .
Answer
cell membrane
A process that takes place only in living beings is called a ……… .
Answer
life process. (The words carbon dioxide and excretion are not used.)
3. Answer the following questions
Describe excretion in the human body in short.
Answer
The human body removes wastes through three main organs:
- Skin: sweat glands give out sweat: extra water, salt and a little urea.
- Lungs: carbon dioxide made by respiration is breathed out, with some water vapor.
- Kidneys: the urinary system removes most other wastes. The two kidneys filter the blood and take out urea, uric acid, extra salt and water, and harmful chemicals, as urine. The two ureters carry the urine to the urinary bladder, which stores it, and it is passed out of the body through the urethra.
How does transportation take place in plants?
Answer
- Plants absorb water and minerals from the soil through their roots. These are carried up to the stem, leaves, flowers and fruits by the xylem, a tissue of long hollow tubes.
- The food made in the leaves by photosynthesis is carried to all parts of the plant, up and down, by the phloem.
- Gases (oxygen and carbon dioxide) enter and leave the leaves through the stomata, and spread to the cells through the air spaces inside.
- Water evaporating from the leaves (transpiration) pulls more water up the xylem.
Explain the importance of respiration.
Answer
- Respiration releases the energy stored in food. Every living thing needs this energy.
- The energy is used for moving, working, thinking, growing, repairing the body, and keeping the body warm.
- It runs all the other life processes: transportation (the heartbeat), excretion, digestion, reproduction.
- Without respiration, cells can’t live: if the brain gets no oxygen for a few minutes, it is damaged.
How do unicellular animals excrete?
Answer
Unicellular animals such as Amoeba have no excretory organs. Their wastes, such as carbon dioxide and ammonia, diffuse out of the cell through the cell membrane into the water around them. Extra water collects in a contractile vacuole, which bursts it out of the cell from time to time.
Describe excretion in plants in short.
Answer
Plants have no special excretory organs.
- They give out the oxygen made in photosynthesis that they don’t use, and the carbon dioxide made in respiration, through the stomata of the leaves (and lenticels in the bark).
- Extra water leaves as vapor through the stomata (transpiration) and as liquid drops through hydathodes at the leaf edges (guttation).
- Other wastes are stored in old leaves and bark, which fall off, or come out as resin, latex, gum and oils.
Explain the respiration process in the human body in short.
Answer
Air is breathed in through the nose, where it is cleaned, warmed and moistened. It passes down the trachea and the two bronchi into the lungs, and along the bronchioles to millions of tiny air sacs, the alveoli. Each alveolus is surrounded by capillaries. Oxygen diffuses from the air in the alveoli into the blood, and carbon dioxide diffuses from the blood into the alveoli; it is breathed out. The oxygenated (pure) blood is pumped by the heart to every cell. In the cells, glucose is broken down using this oxygen to release energy:
glucose + oxygen → carbon dioxide + water + energy.
The diaphragm and the rib muscles move air in and out of the lungs.
Write the differences between respiration in insects and in fish.
Answer
| Respiration in insects | Respiration in fish |
|---|---|
| Organs: spiracles and tracheae (air tubes). | Organs: gills. |
| They take oxygen from air. | They take oxygen dissolved in water. |
| Air enters through spiracles along the sides of the body. | Water enters through the mouth and leaves over the gills. |
| The air tubes carry oxygen straight to the cells; the blood carries little oxygen. | The blood in the gills takes up the oxygen and carries it to the cells. |
What are the differences between excretion in animals and in plants?
Answer
| Excretion in animals | Excretion in plants |
|---|---|
| They have special excretory organs: kidneys, skin, lungs (Malpighian tubules in insects). | They have no special excretory organs; wastes leave through stomata, hydathodes and bark. |
| Wastes: carbon dioxide, urea, uric acid, ammonia, extra water and salt. | Wastes: oxygen, carbon dioxide, water, resin, latex, gum. |
| Excreted wastes are not used again by the body. | Some are used again: carbon dioxide in photosynthesis, oxygen in respiration. |
| Excretion is fast, as animals are active. | Excretion is slow. |
Why do both breathing and the heartbeat speed up while running? Explain.
Answer
When we run, our muscles do much more work and need much more energy. They get it by respiration, so they respire faster: they use oxygen faster and make more carbon dioxide. To supply the extra oxygen and remove the extra carbon dioxide, we breathe faster and more deeply. And the heart beats faster to pump the blood more quickly, carrying oxygen and glucose from the lungs and gut to the muscles, and carbon dioxide from the muscles to the lungs.
Answer these questions about the diagram.
- i.What is the function of this system?
- ii.Name the part marked P.
- iii.In which organ of the body are the alveoli found?
- iv.What is the function of the part marked Q?
- v.In which part does the exchange of oxygen and carbon dioxide take place?
Answer
- i.It is the respiratory system. It takes in oxygen from the air for respiration and gives out carbon dioxide.
- ii.P is the lung.
- iii.The alveoli are in the lungs.
- iv.Q is a bronchus. It carries air from the trachea into the lung, where it branches into the bronchioles that lead to the alveoli, and carries the used air back out.
- v.In the alveoli, through the walls of the alveoli and the capillaries around them.
Draw a neat diagram of the human excretory (urinary) system, and label any four of its parts.
Answer
Draw it as in Figure 5.11: two bean-shaped kidneys high in the back of the belly, a ureter running down from each to the urinary bladder, and the urethra leading out from the bottom of the bladder. Any four of these labels: kidney, ureter, urinary bladder, urethra, renal artery, renal vein.