Transportation and Excretion

What to remember

• Transport carries food, oxygen, water and wastes inside the body. In humans blood, heart and vessels do this (double circulation); in plants xylem carries water and phloem carries food.
• Blood has plasma, red cells, white cells and platelets. Arteries carry blood away from the heart, veins carry blood to the heart, and capillaries link the two.
• Excretion removes metabolic wastes. In humans the kidneys filter blood in nephrons and make urine; in plants wastes are stored or lost as gases, resins and leaf fall.

Transport in humans

Blood. An adult has about 5 to 6 litres of blood. It is a fluid connective tissue.

Haemoglobin is an iron-containing red pigment that joins loosely with oxygen. A normal count: RBC about 5 million per cubic millimetre; WBC about 5,000 to 10,000; platelets about 1.5 to 4 lakh. Blood groups A, B, AB and O were discovered by Karl Landsteiner. Group O is the universal donor (no antigens on RBC) and AB is the universal recipient. The Rh factor is another antigen; Rh-positive and Rh-negative are the two types.

Clotting stops bleeding. Vitamin K and calcium help it. Lymph is a colourless fluid with white cells but no red cells; it returns tissue fluid to the blood and helps in immunity.

Heart. A muscular pump about the size of one's fist, in the chest slightly to the left, covered by the pericardium. It has four chambers: two upper atria (auricles) that receive blood and two lower ventricles that pump blood out. The left ventricle has the thickest wall because it pumps blood to the whole body. Valves between atria and ventricles and in the arteries prevent backflow. The "lub-dup" sounds are due to valves closing.

Double circulation. Blood passes through the heart twice in one complete cycle.

• Pulmonary circulation: right ventricle → pulmonary artery → lungs → pulmonary veins → left atrium. Here the pulmonary artery carries deoxygenated blood and the pulmonary vein carries oxygenated blood.
• Systemic circulation: left ventricle → aorta → body → vena cava → right atrium.

Heart beat rate in a healthy adult at rest is about 72 per minute. Pulse is the beat of the arteries felt at the wrist. Blood pressure is measured by a sphygmomanometer; normal is about 120/80 mm Hg (systolic/diastolic). The stethoscope was invented by Laennec. The circulation of blood was explained by William Harvey.

Fish have a single circulation with a two-chambered heart. Amphibians and most reptiles have a three-chambered heart; crocodiles, birds and mammals have a four-chambered heart.

Common problems. Anaemia is low haemoglobin, often from iron shortage. Hypertension is high blood pressure. Heart attack happens when the blood supply to heart muscle is blocked. Healthy diet, exercise and avoiding tobacco help the heart.

Transport in plants

Water and minerals are absorbed from soil by root hairs and move to the xylem. Xylem vessels and tracheids carry water upward to the leaves. The main forces are root pressure and the pull from transpiration (transpiration pull). Transpiration is the loss of water vapour through stomata of leaves. It cools the plant and pulls water up. About 90 percent or more of absorbed water is lost this way.

Food transport (translocation). Phloem carries food made in leaves to all parts, up and down, using energy. Its sieve tubes and companion cells do this.

Stomata open and close by guard cells. Transpiration is faster in hot, dry, windy conditions and slower in humid air. Potometer is used to measure the rate of water uptake.

Excretion

Excretion is the removal of harmful metabolic waste from the body. Ammonia, urea and uric acid are nitrogenous wastes. Carbon dioxide is removed by the lungs, water and salts by the skin as sweat, and urea by the kidneys.

Human excretory system. It has a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. Kidneys are bean-shaped, reddish-brown organs on either side of the backbone in the abdomen. Renal artery brings blood with waste; renal vein takes away clean blood.

Nephron is the structural and functional unit of the kidney; each kidney has about a million nephrons. Each nephron has a Bowman's capsule with a cluster of capillaries called the glomerulus, and a long tube with a proximal tubule, loop of Henle and distal tubule that opens into a collecting duct.

Urine formation has three steps:

• 1. Ultrafiltration: blood is filtered in the glomerulus into the Bowman's capsule.
• 2. Selective reabsorption: glucose, amino acids, salts and most water are taken back into blood in the tubule.
• 3. Secretion and collection: extra salts and wastes pass into the tubule; urine goes through the ureter to the bladder and is passed out through the urethra.

Normal urine is about 95 percent water, with urea, salts and pigments (urochrome gives the yellow colour). An adult passes about 1 to 1.5 litres a day.

Kidney failure. If kidneys stop working, dialysis (artificial kidney, haemodialysis) is used to clean blood, or a kidney transplant is done. Kidney stones are hard deposits of calcium salts.

Other organs of excretion. Skin: sweat has water, salts and a little urea; it also cools the body. Lungs: carbon dioxide and water vapour. Liver: converts toxic ammonia into urea and breaks down old red cells (bile pigments).

Excretion in other animals. Amoeba removes wastes through the contractile vacuole and by diffusion. Earthworm has nephridia. Insects have Malpighian tubules. Flatworms have flame cells.

Excretion in plants. Plants have no special organs. Wastes are stored in old xylem as gum and resins, in leaves and bark that fall, as latex, tannins and crystals. Oxygen from photosynthesis and carbon dioxide from respiration leave through stomata and lenticels, and extra water leaves by transpiration.

Teaching angle

Learners understand transport by measuring their pulse before and after exercise, studying charts of the heart, and placing a celery stalk or a white flower in coloured water to see xylem at work. Models of a kidney tube help to teach filtration. A teacher can discuss blood donation and the need for safe blood groups in a respectful and simple way.

Exam traps

• The pulmonary artery carries deoxygenated blood; the pulmonary vein carries oxygenated blood.
• Arteries are thick and have no valves; veins have valves.
• Xylem moves water upward; phloem moves food both ways.
• Group O is the universal donor; AB is the universal recipient.
• Ammonia (fish), urea (humans), uric acid (birds).
• Nephron is the functional unit of the kidney, not the neuron.
• Reabsorption occurs in the tubule; filtration occurs at the glomerulus.
• Lymph has no red blood cells.

One-liners

• 1. The heart has four chambers in mammals.
• 2. The left ventricle has the thickest wall.
• 3. Haemoglobin carries oxygen in RBCs.
• 4. Platelets help in blood clotting.
• 5. Karl Landsteiner discovered the ABO blood groups.
• 6. William Harvey explained blood circulation.
• 7. Normal blood pressure is about 120/80 mm Hg.
• 8. Transpiration happens mostly through stomata.
• 9. Phloem transports sucrose.
• 10. Each kidney has about a million nephrons.
• 11. Urea is made in the liver.
• 12. Insects excrete through Malpighian tubules.

Practice questions

1. Which blood cells carry oxygen?

   1. Platelets
   2. Lymphocytes
   3. White blood cells
   4. Red blood cells
   Answer

   D. Red blood cells

   RBCs contain haemoglobin.

2. Which blood component helps in clotting?

   1. Plasma proteins only
   2. Platelets
   3. Red blood cells
   4. White blood cells
   Answer

   B. Platelets

   Platelets form the plug at a wound.

3. The universal blood donor group is

   1. O
   2. B
   3. A
   4. AB
   Answer

   A. O

   Group O has no A or B antigens on RBC.

4. The universal recipient blood group is

   1. B
   2. A
   3. AB
   4. O
   Answer

   C. AB

   AB has neither anti-A nor anti-B antibodies.

5. Who discovered the ABO blood groups?

   1. Laennec
   2. William Harvey
   3. Edward Jenner
   4. Karl Landsteiner
   Answer

   D. Karl Landsteiner

   Landsteiner found the ABO system.

6. The thickest-walled chamber of the human heart is the

   1. left ventricle
   2. right atrium
   3. left atrium
   4. right ventricle
   Answer

   A. left ventricle

   It pumps blood to the whole body.

7. The vessel that carries blood away from the heart is an

   1. vein
   2. capillary
   3. artery
   4. lymph vessel
   Answer

   C. artery

   Arteries carry blood away from the heart.

8. Blood pressure of a healthy adult is about

   1. 80/120 mm Hg
   2. 120/80 mm Hg
   3. 200/100 mm Hg
   4. 60/40 mm Hg
   Answer

   B. 120/80 mm Hg

   Systolic over diastolic.

9. The instrument used to measure blood pressure is the

   1. thermometer
   2. stethoscope
   3. potometer
   4. sphygmomanometer
   Answer

   D. sphygmomanometer

   Sphygmomanometer measures BP.

10. The structural and functional unit of the kidney is the

    1. neuron
    2. nephron
    3. villus
    4. alveolus
    Answer

    B. nephron

    Each kidney has about a million nephrons.

11. The main nitrogenous waste of humans is

    1. ammonia
    2. uric acid
    3. urea
    4. creatinine only
    Answer

    C. urea

    Humans are ureotelic.

12. The main nitrogenous waste of birds is

    1. uric acid
    2. ammonia
    3. urea
    4. glucose
    Answer

    A. uric acid

    Birds are uricotelic.

13. Plant tissue that carries water upward is

    1. cambium
    2. epidermis
    3. phloem
    4. xylem
    Answer

    D. xylem

    Xylem carries water and minerals.

14. Loss of water vapour from the stomata of leaves is called

    1. excretion
    2. translocation
    3. guttation
    4. transpiration
    Answer

    D. transpiration

    It cools the plant and pulls water up.

15. The excretory organs of insects are the

    1. kidneys
    2. Malpighian tubules
    3. flame cells
    4. nephridia
    Answer

    B. Malpighian tubules

    Insects have Malpighian tubules.

16. Earthworm excretes through

    1. nephridia
    2. gills
    3. Malpighian tubules
    4. flame cells
    Answer

    A. nephridia

    Nephridia are the excretory organs of earthworm.

17. Which part of the nephron filters the blood?

    1. Glomerulus with Bowman's capsule
    2. Loop of Henle only
    3. Collecting duct
    4. Ureter
    Answer

    A. Glomerulus with Bowman's capsule

    Ultrafiltration happens at the glomerulus.

18. Which chamber of the heart receives oxygenated blood from the lungs?

    1. Right ventricle
    2. Left ventricle
    3. Left atrium
    4. Right atrium
    Answer

    C. Left atrium

    Pulmonary veins open into the left atrium.

19. Which vessel carries deoxygenated blood from the heart to the lungs?

    1. Pulmonary vein
    2. Pulmonary artery
    3. Aorta
    4. Vena cava
    Answer

    B. Pulmonary artery

    It is the exception: an artery with deoxygenated blood.

20. An adult at rest has a heart beat of about 72 per minute. How many times does the heart beat in 10 minutes?

    1. 7,200
    2. 144
    3. 720
    4. 72
    Answer

    C. 720

    72 x 10 = 720.

21. A person passes 1.5 litres of urine in a day. The volume passed in 4 days is

    1. 7.5 litres
    2. 4 litres
    3. 5.5 litres
    4. 6 litres
    Answer

    D. 6 litres

    1.5 x 4 = 6 litres.

22. If urine is 95% water, the water in 2 litres of urine is

    1. 0.95 litres
    2. 1.95 litres
    3. 1.5 litres
    4. 1.9 litres
    Answer

    D. 1.9 litres

    2 x 0.95 = 1.9 litres.

23. Which one describes dialysis?

    1. Adding oxygen in lungs
    2. Removing the heart valves
    3. Cleaning the blood with an artificial kidney
    4. Changing the blood group
    Answer

    C. Cleaning the blood with an artificial kidney

    Haemodialysis does the work of failed kidneys.

24. Which of these animals has a two-chambered heart?

    1. Fish
    2. Crocodile
    3. Frog
    4. Bird
    Answer

    A. Fish

    Fish have one atrium and one ventricle.

25. Which is a three-chambered-heart animal?

    1. Fish
    2. Frog
    3. Pigeon
    4. Rabbit
    Answer

    B. Frog

    Amphibians have two atria and one ventricle.

26. Translocation of food in plants takes place through

    1. sieve tubes
    2. root hairs
    3. vessels
    4. tracheids
    Answer

    A. sieve tubes

    Sieve tubes of phloem carry sucrose.

27. Which of these is NOT a part of the nephron?

    1. Distal tubule
    2. Loop of Henle
    3. Bowman's capsule
    4. Ureter
    Answer

    D. Ureter

    The ureter is outside the nephron.

28. The colour of normal urine is mainly due to

    1. chlorophyll
    2. urochrome
    3. bile salts
    4. haemoglobin
    Answer

    B. urochrome

    Urochrome gives the yellow colour.

29. Plants get rid of some wastes by

    1. using kidneys
    2. sweating
    3. shedding leaves and bark
    4. using lungs
    Answer

    C. shedding leaves and bark

    Wastes are stored in leaves and bark that fall.

30. Consider the statements. 1. Veins have valves. 2. Arteries carry blood to the heart. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Arteries carry blood away from the heart.

31. Consider the statements. 1. Xylem carries water upward. 2. Phloem carries food in both directions. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

32. Consider the statements. 1. Lymph contains red blood cells. 2. Lymph helps in immunity. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Lymph has no RBC.

33. Consider the statements. 1. The glomerulus filters the blood. 2. Reabsorption of glucose takes place in the ureter. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Reabsorption happens in the tubules.

34. Consider the statements. 1. Human heart shows double circulation. 2. Fish heart shows double circulation. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Fish have single circulation.

35. Consider the statements. 1. Transpiration cools the plant. 2. Transpiration helps in the upward pull of water. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

36. Consider the statements. 1. Ammonia is the main waste of most fishes. 2. Urea is formed in the liver. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

37. Consider the statements. 1. Haemoglobin contains iron. 2. Anaemia is caused by a shortage of haemoglobin. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

38. Match the animal with the excretory structure. (a) Earthworm (b) Insect (c) Flatworm (d) Human (p) Flame cells (q) Kidney (r) Nephridia (s) Malpighian tubules

    1. a-r, b-p, c-s, d-q
    2. a-s, b-r, c-p, d-q
    3. a-q, b-s, c-p, d-r
    4. a-r, b-s, c-p, d-q
    Answer

    D. a-r, b-s, c-p, d-q

    Standard excretory structures.

39. Match the blood component with its function. (a) Plasma (b) RBC (c) WBC (d) Platelets (p) Clotting (q) Defence (r) Carries nutrients and hormones (s) Carries oxygen

    1. a-s, b-r, c-q, d-p
    2. a-r, b-s, c-q, d-p
    3. a-r, b-q, c-s, d-p
    4. a-r, b-s, c-p, d-q
    Answer

    B. a-r, b-s, c-q, d-p

    Plasma carries substances; RBC oxygen; WBC defence; platelets clotting.

40. Arrange the path of urine in the correct order.

    1. Kidney, bladder, ureter, urethra
    2. Kidney, urethra, bladder, ureter
    3. Ureter, kidney, bladder, urethra
    4. Kidney, ureter, bladder, urethra
    Answer

    D. Kidney, ureter, bladder, urethra

    Urine flows down from kidney to outside.

41. Arrange the path of blood in pulmonary circulation.

    1. Left ventricle, pulmonary artery, lungs, pulmonary vein, right atrium
    2. Right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium
    3. Right atrium, pulmonary vein, lungs, pulmonary artery, left ventricle
    4. Right ventricle, aorta, lungs, vena cava, left atrium
    Answer

    B. Right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium

    Blood goes from heart to lungs and back.

42. To show that water rises through the xylem, a teacher places a white flower in coloured water. The colour appears in the petals because

    1. the flower makes dye
    2. roots make the colour
    3. phloem carries colour down
    4. xylem carries the coloured water up
    Answer

    D. xylem carries the coloured water up

    Xylem lifts water upward.

43. Learners count their pulse before and after running on the spot. The aim of the activity is to show

    1. pulse is not related to the heart
    2. the heart stops after exercise
    3. blood has no relation to the heart
    4. heartbeat rate increases with exercise
    Answer

    D. heartbeat rate increases with exercise

    Exercise raises heart rate.

44. Which of the following is a function of the human skin in excretion?

    1. Filtering blood
    2. Removing water and salts as sweat
    3. Making urea
    4. Storing bile
    Answer

    B. Removing water and salts as sweat

    Sweat has water, salts and a little urea.

45. The organ that converts toxic ammonia into urea is the

    1. liver
    2. lung
    3. kidney
    4. spleen
    Answer

    A. liver

    The liver forms urea.