Topic 4: Transportation Of Minerals Of Living Things – Biology Notes Form 2
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TRANSPORT OF MATERIALS IN LIVING THINGS
Is the movement of oxygen and nutrients to all body cells and removal of body wastes from the body cells.
IMPORTANCE OF TRANSPORT OF MATERIALS
1. Transport enables distribution of antibodies.
2. Transport facilitates the movement of food and oxygen absorbed into different parts of the body.
3. Transport helps to remove waste products from their organs of synthesis.
4. Transport enables hormones to move from the gland to the target area.
WAYS OF TRANSPORTATION OF MATERIALS IN LIVING THINGS
There are three ways through which materials are transported in living things, these are;-
i. Diffusion
ii. Osmosis
iii. Mass flow
NB: Diffusion and osmosis occur without using energy. This type of movement of materials is known as passive transport
PASSIVE TRANSPORT
Is the transport of materials which occurs without the need of energy through the cell membrane.
ACTIVE TRANSPORT
Is the transport of materials which occurs with the need of energy across the cell membrane against a concentration gradient.
CONCENTRATION GRADIENT
Is a difference in concentration of a substance between two regions.
DIFFUSION, OSMOSIS AND MASS FLOW
DIFFUSION
Is the movement of particles from a region of high concentration to a region of low concentration.
Things which can diffuse includes small molecules such as:
— Oxygen
— Carbondioxide
— Water
— Some vitamins such as A, D, E and K
— Amino acids
— Fatty acids and glycerol
IMPORTANCE OF DIFFUSION IN LIVING THINGS
1. Diffusion enables the passing of important substances in and out of the cell.
2. Diffusion enables absorption of digested food in the ileum to the blood system.
3. Enable plants to absorb nutrients and mineral salts.
4. Diffusion enables manufactured food to be transported and distributed from the leaves to other parts of the plants.
5. Diffusion enables the removal of nitrogenous wastes such as urea and ammonia.
6. Diffusion enables gaseous exchange in the lungs of animals and in the leaves of plant.
FACTORS WHICH AFFECTING THE RATE OF DIFFUSION
1. CONCENTRATION GRADIENT
When the concentration gradient is high, diffusion is faster when the concentration gradient is low, diffusion is low.
NB: A big difference between the concentration of the molecules in two regions leads to a faster rate of diffusion.
2. SURFACE AREA TO VOLUME RATIO
The higher it is the faster the diffusion rate.
3. THICKNESS OF MEMBRANES AND TISSUES
The thin the membrane enhance higher rate of diffusion than thick membranes.
4. SIZE OF MOLECULES
Small and light molecules diffuse faster than large and heavy molecules.
5. TEMPERATURE
Increase in temperature increases the rate of diffusion. Decrease in temperature decreases the rate of diffusion.
OSMOSIS
Is the movement of water molecules from a region of high water concentration to a region of low water concentration through a semi-permeable membrane.
In the living things, the cell membrane acts as a semi-permeable membrane.
Osmosis takes place when there is difference in concentration between cytoplasm and tissue fluid.
TISSUE FLUID
Is a fluid found in the interstitial spaces that bathes and surrounds the cells of malticellular animals.
TYPES OF SOLUTIONS
There are three types of solutions:
The two solutions have the same osmotic pressure.
A hypotonic solution has low osmotic pressure.
A cell placed in such a solution gains water by osmosis.
A hypertonic solution has high osmotic pressure.
A cell placed in such a solution loses water by osmosis.
NB; Osmosis is caused by osmotic pressure.
QN: Differentiate between osmotic pressure and osmotic potential, turgor pressure and wall pressure.
Osmotic pressure: Is the pressure that draws water molecules from lowly concentrated solution to highly concentrated solution until an equally concentrated solution is attain (isotonic solution is attained) while
Osmotic potential: is a hidden pressure that draws water molecules through a semipermeable membrane from less concentrated to high concentrated solution.
Turgor Pressure: is the pressure which is created when plant cell absorb water causing the vacuole to enlarge. OR Is the pressure which exerted from the cell membrane towards the cell wall while
Wall Pressure: Is the pressure which exerted from the wall towards the cell membrane.
EFFECTS OF OSMOSIS IN PLANTS AND ANIMAL CELLS
When a plant or animal cell is placed in an isotonic solution, the cells will neither absorb nor loss of water.
EFFECTS OF OSMOSIS IN ANIMAL CELLS
When Placed In Hypotonic Solution (less concentrated solution)
When red blood cell is placed in hypotonic solution, the cell will absorb water by osmosis as the result will swell and burst. This condition is called heamolysis.
HAEMOLYSIS
Is the process by which red cells burst due to water gain by osmosis when placed in hypotonic solution.
When Placed In Hypertonic Solution (high concentrated solution)
When ared blood cell is placed in hypertonic solution, the cell will loss water by osmosis and shrink.
— This condition is called crenation
CRENATION
Is the process by which red blood cell shrink due to loss of water by osmosis when placed in hypertonic solution.
EFFECTS OF OSMOSIS IN PLANT CELLS
(a) When Placed In A Hypotonic Solution
When plant cell is placed in a hypotonic solution the cell absorbs water by osmosis and become turgid.
TURGIDITY
Is the process by which a plant cell becomes firm and rigid due to gain of water by osmosis when placed in hypotonic solution.
BIOLOGICAL IMPORTANCE OF TURGIDITY
— Helps the plants to maintain their shape.
b) When Placed In A Hypertonic Solution
When a plant cell is placed in a hypertonic solution, the cell will loss water by osmosis as a result, the cell will shrink and become flaccid.
— This is known as plasmolysis.
PLASMOLYSIS
Is the process by which cell shrinks due to loss of water by osmosis when placed in hypertonic solution.
DEPLASMOLYSIS
Is the process which occurs when the flaccid cell gains water when placed in distilled water and regains its original shape.
EXAMINATION QUESTIONS
1. Explain what will happen if red blood cell is placed in hypotonic solution?
ANSWER:
The cell will absorb water by osmosis as the result will swell and burst
2. Turgidity in plant is said to be biologically significant. Explain
ANSWER
The biological importance of cell turgidity in plants is to maintain the shape of plant cell.
3. Why plants wilt or die when fertilizers are excessively applied?
ANSWER
Because the soil becomes more concentrated than the cell sap, hence plants lose water to the soil by osmosis.
NB: Protozoans like amoeba and euglena can overcome crenation and haemolysis by possessing a contractile vacuole. The contractile vacuole absorbs water from the cytoplasm and moves it to the cell membrane and empties it out.
IMPORTANCE OF OSMOSIS
1. Osmosis enables uptake of water by root hairs from the soil.
2. Helps in maintaining shapes of cells by turgor pressure.
3. Osmosis helps in opening and closing of stomata.
4. Enables reabsorption of water from the kidney tubule.
5. Enables absorption of water in the intestines.
6. Osmosis enables food preservation through salting.
FACTORS AFFECTING THE RATE OF OSMOSIS
The followings are factors affecting the rate of osmosis
1. CONCENTRATION GRADIENT
The greater the difference between the two concentrations the greater the speed of osmosis.
2. TEMPERATURE
Increase in temperature increases the rate of osmosis.
3.THICKNESS OF MEMBRANE
Osmosis is faster in thin membranes than in thick ones.
4. NATURE OF SOLVENT
MASS FLOW
Is the bulk movement of substances from one region to another due to the difference in pressure between the two regions.
NB: Mass flow occurs within a cell or along a vessel.
This mode of transport is important in large complex organisms where substances are required in large amounts and also have to be transported over a greater distances.
Example of systems where mass flow occurs are:
i. The circulatory system
ii Respiratory system
iii. The lymphatic system
iv. Digestive system
Importance of mass flow
In plants
i. Mass flow enables transportation of water and minerals salts from the roots to the manufacture area(leaves) through xylem vessel.
i. Mass flow enables transportation of food and water within the blood vessel to various parts of the body.
ii. Mass flow enables transportation of respiratory gases in the respiratory system.
iii. Mass flow enables transportation of blood in the circulatory systems and lymph in lymphatic system.
Differences between diffusion, osmosis and mass flow
| Diffusion | Osmosis | Mass flow |
| The Substance transported are gases and liquids | Substance transported is water | Substances transported are solids, liquids and gases |
| There is no transportation structures | The transportation structure isSemi-permeable membrane | The transportation structures isCytoplasm or vessels |
| The causes of movement is diffusion gradient | The causes of movement is osmotic pressure | The causes of movement is difference in pressure |
TRANSPORT OF MATERIALS IN MAMMALS
Mammals: are complex multicellular organisms whose bodies are made up of numerous cells and tissues.
► In this case, diffusion alone is not enough to ensure efficient carrying out of life process. Therefore mammals have an elaborate transport system called circulatory system.
CIRCULATORY SYSTEM
Is the system that permits blood to circulate and transport nutrients, oxygen, carbon dioxide and hormones.
– Circulatory system is also called cardiovascular system.
COMPONENTS OF THE CIRCULATORY SYSTEM
Circulatory system is made up or composed of the three components namely:
1. Heart (pumping organ)
2. Blood (transporting fluid)
3. Blood vessels (tubes through which blood flows)
1. THE HEART
Is an organ for pumping blood in the mammalian’s body.
The human heart is located in the chest cavity between the lungs.
THE STRUCTURE OF THE MAMMALIAN HEART
The external structure of the mammalian heart
The heart is made up of specialized strong muscles called cardiac muscles.
The heart is enclosed by a double membrane of tough inelastic membrane called pericardium.
Between the two membranes there is a fluid called pericardial fluid.
The heart has its own blood supply through its blood vessels called coronary artery and coronary vein
| STRUCTURE | ITS FUNCTIONS |
| Cardiac muscles |
|
| Pericardium |
|
| Pericardial fluid |
|
| Coronary artery |
|
| Coronary vein |
|
NB: Cardiac muscles are found only in the heart.
The external structure of the mammalian heart is as shown in the labeled diagram below
THE INTERNAL PART OF THE HEART
The heart contains four chambers
Two upper chambers which are right auricle and left auricle and two lower chambers which are right ventricle and left ventricle
Upper chambers are called auricles or atria and lower chambers are called ventricles
The ventricles are bigger than auricles and their walls are thicker than those of auricles because they are pumping blood to all parts of the body.
FOUR CHAMBERS OF THE HEART AND THEIR FUNCTIONS
| Chamber | Its function |
| Right ventricle | It receives deoxygenated blood from the right auricleIt also pumps blood to the lungs via the pulmonary artery. |
| Right auricle |
It receives deoxygenated blood from the body tissue through the venacava. |
| Left ventricle | It receives oxygenated blood from left auricle |
| Left auricle | It receives oxygenated blood from the lungs via the pulmonary vein |
EXAMINATION QUESTION
Why does the left ventricle have a thicker wall than the right ventricle?
ANSWER:
Because the right ventricle pumps blood to the lungs while the left ventricle pumps blood to the rest of the body parts.
Why does the ventricle wall are thicker than those of the auricle?
Answer: Because
The ventricles pump blood to a greater distance than the auricles.
Auricles pump blood to the ventricles while the ventricles pump blood to the other parts of the body.
The diagram of internal structure of the mammalian heart
The heart is divided into two sides, the left side and right side
The left side and right side of the heart are completely separated by a wall called septum
SEPTUM
Is a thick muscular wall between the right side of the heart and left side of the heart.
Function of the septum
Septum prevents mixing of the oxygenated blood and deoxygenated blood.
HEART VALVES
Are the valves that prevent back flowing of blood.
Function of the valves
To prevent the back flowing of the blood.
The valves ensure that blood flows in one direction only.
There are three valves in the heart namely:
Tricuspid valve
Bicuspid valve
(iii)Semilunar valve
TRICUSPID VALVE
Is the valve found between the right auricle and the right ventricle.
Function of tricuspid valve
Tricuspid valve prevents the back flow of blood from right ventricles to right auricle.
BICUSPID VALVE
Is the valve found between the left auricle and the left ventricle.
Function of bicuspid valve
Bicuspid valve prevents back flow of the blood from the left ventricle to the left auricle.
SEMI-LUNAR VALVE
Is the valve found at the lower end of pulmonary artery and aorta.
Function of the semilunar valve
Semi-lunar valve prevents blood from flowing back into the ventricle
SINOATRIAL NODE (SAN)
Is a small patch of muscle in the right atrium which sets the time and rate of cardiac muscle concentration
ADAPTATION OF THE MAMMALIAN HEART TO ITS FUNCTIONS
The mammalian heart is adapted to carry out its function because it has the following features:
1. Cardiac muscles which do not get fatigue hence pump blood without stopping.
2. Pericardium that surrounds and prevents the heart from physical damage.
3. Pericardial fluid which prevents friction when the heart beats.
4. Valves which prevent the back flow of blood.
5. Septum which prevents mixing of the oxygenated blood and deoxygenated blood.
6. The left ventricle has a thick muscular wall to pump blood at higher pressure to the distant body tissues.
7. Its own blood supply for supplying nutrients and removing wastes.
8. The heart has sinoatrial node to sets time and rate of contraction and relaxation of cardiac muscle.
9. It is supplied with nerves which controls the rate of heart beat depending on the body requirements.
BLOOD VESSELS
Are tubes through which blood flows.
TYPES OF BLOOD VESSELS
A mammal has three main types of blood vessels namely:
i. Arteries
ii. Veins
iii. Blood capillaries
ARTERIES
Are blood vessels which carry blood away from the heart to all parts of the body. Arteries carry blood under high pressure The large and main artery is aorta.
All arteries transport oxygenated blood, except pulmonary artery which transport deoxygenated blood from the heart to the lungs.
Branches of arteries
Arteries are divided into smaller blood vessels called arterioles
Function of arterioles
Arterioles supply blood to major organs.
The arterioles branches to form small tubes called blood capillaries.
The structure of an artery
Adaptations of arteries
They have small lumen which increases pressure to pump the blood.
They have thick, muscular and elastic walls to transport blood under high pressure without rupturing.
VEINS
Are blood vessels which carry blood from body parts to the heart.
The large and main vein is the venacava
Superior vena cava and inferior vena cava join together to form vena cava
All veins carry deoxygenated blood except pulmonary vein, which carries oxygenated blood from the lungs to the heart.
All veins also carry blood with less nutrients and more waste product except hepatic portal vein and renal vein.
Function or Role of veins
To carry blood from body parts to the heart.
Branches of vein
Veins divided into smaller blood vessels called venules.
The branching of blood vessels ensures that each part of the body is supplied with blood.
Blood may be rich in oxygen or carbon dioxide.
Oxygenated blood
Is the blood rich in oxygen.
Deoxygenated blood
Is the blood rich in carbon dioxide.
The structure of veinThe diagram of valves in vein
Adaptation of veins
i. They have thinner, less elastic, less muscular walls with large lumen to carry blood under low pressure.
ii. They have valves which prevent back flow of blood.
BLOOD CAPILLARIES
Are the smallest blood vessels that carry blood to individual cells.
They are highly branched to allow exchange of materials between the blood and the cells.
THE STRUCTURE OF CAPILLARY
ADAPTATIONS OF BLOOD CAPILLARIES
i. They are numerous to increase the surface area.
ii. They are very close to the tissue for easy exchange of materials.
iii. They have very thin walls which allow easy diffusion of materials between blood and body cells.
iv. They have very small lumen which forces red blood cells to squeeze and hence oxygen diffuses into body cells.
DIFFERENCES BETWEEN ARTERIES, VEINSAND CAPILLARIES
| Arteries | Veins | Capillaries |
| (i) They have small lumen. | They have large lumen | They have a very small lumen. |
| (ii) They have thick, muscular and elastic walls. | They have thinner, less muscular and less elastic walls. | They have thinnest and one-cell thick walls. |
| (iii) Blood flow under high pressure. | Blood flow under low pressure. | Blood flow under very low pressure. |
| (iv) They carry blood away from the heart. | They carry blood towards the heart. | They carry blood from arteries to veins. |
| (v) All carry oxygenated blood except pulmonary artery. | All carry deoxygenated blood except pulmonary vein. | They carry either oxygenated or deoxygenated blood. |
| (vi) They have no valves except at the base of aorta and pulmonary artery. | They have valves at intervals. | They have no valves. |
| (vii) They are located deep in the body. | They are located near the surface of the skin. | They are found between arteriole and venule. |
| (viii) Colour of blood is bright red(because it is rich in oxygen) | Colour of blood in veins is brown red. | Colour of blood in capillaries is brown red. |
SOME OF THE MAJOR BLOOD VESSELS IN THE HUMAN BODY
| BLOOD VESSELS | FUNCTION | |
| Aorta | It carries oxygenated blood from the heart to all parts of the body. | |
| Venacava | Carries deoxygenated blood from all body parts to the heart. | |
| Inferior venacava | Carries deoxygenated blood from the lower parts of body.— For example from the lower limbs, kidney, liver, stomach and small intestines. | |
| Superior venacava | Carries deoxygenated blood from the upper parts of the body.
— For example from the head, neck and upper limbs to the heart. |
|
| Pulmonary vein | Carries oxygenated blood from the lungs to the heart. | |
| Pulmonary artery | Carries deoxygenated blood from the heart to the lungs.— Deoxygenated blood is taken from the heart to the lungs in order to collect oxygen. | |
| Hepatic artery | Carries oxygenated blood to the liver | |
| Hepatic vein | Transports deoxygenated blood from the liver to the inferior venacava | |
| Hepatic portal vein | Carries blood containing digested food from the intestine to the liver | |
| Renal artery | Carries oxygenated blood to the kidney. | |
| Renal vein | Carries blood from the kidney to the inferior venacava | |
| Femoral artery | Carries oxygenated blood from the heart to the legs. | |
| Femoral vein | Carries deoxygenated blood from the legs to the heart. | |
| Mesenteric artery | Carries blood from the heart to the stomach and intestines. | |
| Carotid artery | Carries blood from the heart to the brain. |
BLOOD
Is a liquid made up of two main components, the blood cells and the blood plasma.
NB: An adult human has 4 to 6 litres of blood. The pH of blood is 7.4
FUNCTION OF MAMMALIAN BLOOD
1. To transport oxygen from the lungs to other part of the body.
2 To transport nutrients from the small intestine to other parts of the body.
3. To transport of waste materials from where they are produced to the organs of excretion.
4. To transport hormones from endocrine glands to their target organs
5. Helps in body temperature regulation.
6. Helps in body defense against microorganisms
THE MAIN COMPONENTS OF THE BLOOD
Blood is made up of two main components, namely:-
(i) Blood cells
(ii) Blood plasma
NB: Blood cells make up the solid part of the blood while plasma is a liquid part of the blood
BLOOD PLASMA
Is a pale-yellow fluid made of about 90% water and some dissolved substances such as glucose, urea fatty acids and waste materials.
Serum: is the blood plasma from which blood cells and fibrinogen are removed.
FUNCTIONS OF PLASMA
Transporting nutrients throughout the body.
Fighting infections since it contains antibodies.
(iii)Carrying body waste to be removed by the body.
(iv) Carrying and transporting some hormones.
BLOOD CELLS
There are three types of blood cells, namely:
i. Red blood cells or erythrocytes
ii. White blood cells or leucocytes
iii. Platelets or thrombocytes
RED BLOOD CELLS (erythrocytes)
Are disc shaped cells whose main function is to carry oxygen.
They are biconcave in shape (disc-shaped) to increase the surface area.
Functions of Red Blood Cells
To transport oxygen from the lungs to other part of the body.
To transport carbon dioxide from the body tissues to the lungs.
Adaption of Red Blood Cells
Red blood cells have the following adaptations:
They have haemoglobin which carries oxygen.
They are many in number for effectively transport of gases. (About 5-6 million per 1 mm3 of blood).
They lack nuclei to increase surface area for taking up oxygen.
Their membranes are flexible and bend in many directions without being damaged. Therefore, they can pass through the smallest blood vessels to deliver oxygen to where it is needed.
THE STRUCTURE OF RED BLOOD CELL
NB: Red blood cells have short lifespan of about 120 days. The liver and spleen destroy old blood cells and release haemoglobin for the formation of new cells.
HAEMOGLOBIN
Is a red pigment in red blood cells responsible for transportation of oxygen.
When haemoglobin combine with oxygen form a compound known as oxyhaemoglobin
When haemoglobin combines with carbondioxide to form carbaminohaemoglobin compound.
WHITE BLOOD CELLS (Leucocytes)
Are blood cells concerned with body immunity.
White blood cells are formed in the bone marrow of long bones such as humerus and in lymph nodes.
They have an irregular shape and a large nucleus.
TYPES OF WHITE BLOOD CELLS
There are two types of white blood cells namely:
Phagocytes
Lymphocytes
PHAGOCYTES OR GRANULOCYTES
Are cells which have irregular nuclei.
Function of Phagocytes
i. To engulf and digest pathogens in the body.
ii. To remove old and damaged body cells.
PHAGOCYTOSIS
Is the process by which a phagocyte engulfs and digest a pathogen. Diagram of phagocyte
a) LYMPHOCYTES
Are cells formed in lymph nodes.
FUNCTION OF LYMPHOCYTES
To produce antibodies.
Diagram of lymphocyte
WAYS IN WHICH LYMPHOCYTES PROTECT THE BODY AGAINST PATHOGENS
i) Produce anti-toxins that neutralize the toxin produced by pathogens.
ii) Some antibodies digest the cell membranes and cell walls of pathogens.
iii) Some antibodies cause the pathogens to clump together where they die, and are ingested by phagocytes.
Functions of white blood cells
i. To protect the body against infections by engulfing and destroying pathogens.
ii. Producing substances that neutralize toxins produced by pathogens.
iii. Causing cramping together of foreign materials in the body.
iv. Killing infected body cells.
v. Preventing clotting in damaged tissues.
Adaptations of White Blood Cells or Leucocytes
i. They have no definite shape for easy fighting against pathogens.
ii. They have large nuclei which contain many genes for the control of the production of antibodies.
iii. Their cytoplasm contains enzymes which digest the pathogens.
iv. Their cell membranes have a sensitive surface to enable the cell to detect foreign bodies and destroy them.
v. A flexible cell membrane which enables them to penetrate through small gaps in the capillaries and travel to where they are needed in the body.
PLATELETS
Are small disc-shaped fragments produced in the bone marrow. They have no nuclei
– They have irregular shape.
– During bleeding, they clump together to form a network or mesh hence bleeding stops.
FUNCTION OF THE PLATELETS
Platelets have the following adaptations:
1. Platelets are the smallest and hence easy to clump together.
2. They have enzymes which make them capable of clamping and sticking together.
3. They release chemicals which help in constricting the blood vessels to reduce bleeding and attract more platelets.
Components of blood clotting
i. Platelets
ii. Thromboplastin
iii. Vitamin K and calcium
iv. Thrombin
PROCESS OF BLOOD CLOTTING (coagulation)
1. Platelets at the site of an injury produce thromboplastin which starts off the clotting process.
2. Thromboplastin, with the help of vitamin K and calcium neutralizes heparin, an anticoagulant in blood.
3. Heparin converts prothrombin (which is an inactive plasma protein) to thrombin (an active plasma protein).
4. Thrombin catalyzes the conversion of soluble fibrinogen to insoluble fibrin.
5. Fibrin forms a network of fibers that traps debris and blood cells.
6. The result is a clot at the site of the wound preventing further loss of blood.
EFFECTS OF HIV ON WHITE BLOOD CELLS
1. HIV destroys helper-T cells in the following ways:
2. It reproduces inside the helper-T cell, then ruptures the cell’s membrane and the new viruses are released.
3. It alters the helper-T cells so that when it responds to an infection, it kills itself instead of dividing to form new cells.
4. It marks helper-T cells as targets for destruction by other cells in immune system.
5. It causes the fusion of many helper-T cells to form a giant cell. Such a cell can survive but it cannot perform normal helper-T cell functions.
NB: HIV lowers the body’s immunity significantly making it vulnerable to opportunistic infections.
DIAGRAM SHOWS HIV ATTACKING HELPER-T CELL
BLOOD GROUP AND BLOOD TRANSFUSION
Blood groups
There are four blood groups namely:-
i) Blood group A
ii) Blood group B
iii) Blood group AB
iv) Blood group O
Factors that considered during grouping of human blood
There are two factors considered during grouping of human blood, these are:
1. Type of antigens present on red blood cells membrane
2. Type of antibodies present in the blood plasma
Ways used in grouping of human blood
1. The ABO system
2. Rhesus factor
THE ABO SYSTEM
Is the system of grouping blood depends on the presence or absence of antigen A or B on the membrane of red blood cells and on the presence or absence of antibody a or b in the blood plasma.
NB: Red blood cells contain protein on their surface membrane known as antigens.
ANTIGEN
Is a chemical substance that stimulates production of antibody.
TYPES OF ANTIGENS
There two types of antigen present on the membrane of red blood cell namely:
i) Antigen A
ii) Antigen B
Antigens determine blood groups
Example
i. A person with antigen A has blood group A
ii. A person with antigen B has blood group B
iii. A person with antigen A and B has blood group AB
iv. A person with no antigen has blood group O
NB: Plasma has a certain protein known as antibodies
ANTIBODY
Is a protein produced by the body’s immune system to fight an antigen.
TYPES OF ANTIBODIES
There are two types of antibodies, namely:
i) Antibody a ii) Antibody b
NB: If antibody comes into contact with a corresponding antigen, for example antibody a and antigen A
agglutination occurs.
AGGLUTINATION
Is the clamping together of red blood cells when antibody comes into contact with a corresponding antigen.
The table below summarizes the various blood groups and the antigens and antibodies present in them.
| Blood group | Antigen in red blood cells | Antibody in the plasma |
| A | A | b |
| B | B | a |
| AB | A and B | None |
| O | None | a and b |
RHESUS FACTOR
Is an antigen present on the red blood cells apart from antigen A and B.
This antigen is called Rhesus antigen
The presence of Rhesus antigen gives blood the positive sign. E.g. A+, B+, AB+ and O+
Lack of this Rhesus antigen gives blood the negative sign. E.g. A–, B–, AB– and O–
QN What would happen if a Rh– mother gives birth to Rh+ child?
i. If a Rh– mother gives birth to a Rh+ child, the mother’s body will respond by producing Rhesus antibodies which will reach foetus’ blood and destroy some of the foetus red blood cells, hence the born child will survival because the destruction is minimal.
ii. If the same mother gets pregnant again with Rh+ child, a lot of red blood cells of the foetus will be destroyed leading to the death of the foetus in the last pregnancy.
iii. This condition is known as haemolytic diseases of the new born or erythroblastosis foetalis.
What would happen if a person with Rh– receives blood from a Rh+ donor?
iv. If a person with Rh– receives blood from a Rh+ donor, agglutination will occurs.
2. Mention two modern ways, a child can be saved from erythroblastosis foetalis.
(i) Transfusion of blood to the foetus while still in the uterus.
(ii) Injecting the mother with anti-rhesus antibody, which prevents the antibody –antigen reaction.
NB: About 85% of total human population have Rhesus antigen and they are referred to as rhesus positive (Rh+).
The remaining 15% lack Rhesus antigen and they are referred to as rhesus negative (Rh–)
BLOOD TRANSFUSION
Is the transfer of blood from one person to another through blood vessels.
DONOR
Is a person who gives blood
RECIPIENT
Is a person who receives the blood.
In order for blood transfusion to be successful, the blood of the donor and that of the recipient must be compatible.
BLOOD COMPATIBILITY AND BLOOD INCOMPATIBILITY
Blood compatibility: is the state in which the blood of the donor and the recipient mix without agglutination.
Blood incompatibility: is the state in which agglutination occurs when the blood of the donor is transfered to the recipient.
Example: a person of blood group A receives blood from a person of blood B, the recipient’s body produces antibodies against antigen B. this is because the antigen is seen as foreign material.
Blood compatibility depends on the blood groups of the donor and the recipient.
BLOOD GROUP A
A person of blood group A can donate blood to a person of blood group A and AB.
A person of blood group A can receives blood from blood group A and O
BLOOD GROUP B
A person of blood group B can donate blood to a person of blood group B and AB.
A person of blood group B can receives blood from blood group B and O
BLOOD GROUP AB
A person of blood group AB can donate blood to a person of blood group AB only.
A person of blood group AB can receives blood from all blood groups (A, B, AB and O) NB: A person of blood group AB is called universal recipient because can receive blood from all blood groups.
BLOOD GROUP O
A person of blood group O can donate blood to all blood groups (A, B, AB and O).
A person of blood group O can receives blood from blood group O only.
NB: A person of blood group O is called universal donor because can donate blood to all blood groups.
The table below shows the compatibility of blood groups
PRECAUTIONS TAKEN DURING BLOOD TRANSFUSION
1. The doctor should establish the blood group of a recipient to prevent agglutination.
2. The blood should be screened to ensure that there is no any pathogen.
3. The donor should be aged from 18 to 60 years old and healthy.
4. The blood should be taken from vein, probably in the arm.
5. The donor should be given biscuits or glucose after donating.
6. An anticoagulant should be put in the blood to prevent clotting.
7. Should be stored above freezing point.
ADVANTAGES OF BLOOD TRANSFUSION
1. It saves lives of people during operation or people involved in an accident.
2.It increases the amount of blood in the body.
3. It helps to control diseases such as leukemia.
DISADVANTAGES OF BLOOD TRANSFUSION
1. It may causes transmission of diseases if blood screened is not done well.
2. It may results into agglutination if blood groups are not compatible
3. Sometimes the donor can develop health problems. For example the body can produces excess blood than normal.
BLOOD CIRCULATION
Is the movement of blood from the heart to body parts and back to the heart.
Less complex organisms such as fish, exhibit single circulation whereby the blood goes through the only once to complete circulation.
BLOOD CIRCULATION IN HUMAN
Human being exhibit double circulation
Double circulation: is a circulation whereby the blood passes through the heart twice for each to complete circulation.
The double circulation involves pulmonary circulation and systematic circulation.
PULMONARY CIRCULATION
Is the movement of blood from the heart to the lungs and back to the heart.
Forms of blood are transported in the body
There are two forms of blood transported in the body, namely:
1. Oxygenated blood (blood which is rich in oxygen and must be supplied to the body parts)
2. Deoxygenated blood (blood which is rich in carbondioxide and must be removed from the body)
During pulmonary circulation
Deoxygenated blood from all body parts (except the lungs) enters the right auricle through the venacava.
When the right auricle is full, the muscles contract and blood is forced into the right ventricle.
The tricuspid valve prevents the back flow of blood to the right auricle.
At this point the right auricle relaxes to bring more deoxygenated blood.
When the right ventricle is full, it contracts and blood is pushed out of the heart to the lungs through the pulmonary artery.
In the lungs, the blood is oxygenated, and then flows back to the heart through pulmonary vein.
Diagram showing the blood circulation in the heart
STEMATIC CIRCULATION
Is the movement of blood from the heart and to all body parts except the lungs.
During systematic circulation
The oxygenated blood from the lungs is returned back to the heart via the pulmonary vein.
When the left auricle is full, it contracts and the blood is forced into the left ventricle.
The bicuspid valve closes to prevent back flow.
At the same time, the left ventricle relaxes to bring in oxygenated blood from the lungs.
When the left ventricle is full it contracts and blood is forced to the largest artery, the aorta.
From the aorta the oxygenated blood is distributed to other body parts except the lungs.
A WELL LABELLED DIAGRAM OF THE HUMAN BLOOD CIRCULATORY
SYSTEM
IMPORTANCE OF BLOOD CIRCULATION
1. Transports useful materials such as oxygen and food nutrients to all body parts.
2. Transports waste products to excretory organs where they can be removed.
3.Protects the body against diseases and infections through white blood cells.
4. Regulates body temperature by dispersing body heat as it moves.
5. Transports hormones from the organs where they are produced to the organs where they are needed.
6. Facilitating blood clotting to prevent loss of blood.
MEASURING PULSE RATE AND BLOOD PRESSURE
PULSE
Refer to a regular beats of blood at some points of body caused by the pumping of the heart.
PULSE RATE
Is the number of times the heart beats per minute.
A person in normal health, the pulse occurs 72 times per minute.
It is also known that the rate of the pulse varies from 150 beats per minute in the embryo of a human being to about 60 in the aged.
Detection of the pulse
The pulse can be felt in any artery that passes over a solid structure such as bone or cartilage closes the skin surface.
The points where pulse can be detected includes, the wrist, neck, below the ear, behind the knee, on the inside of the elbow and near the ankle joint.
Factors affecting the pulse rate
The pulse rate can be affected by the following factors:-
1. Activities
In vigorous activities the pulse rate increases because the heart beats faster to supply more oxygen to the body.
2. Health
When a person is sick the pulse rate increases because the heart beats faster to supply more oxygen to the body.
3. Age
Children have high pulse rate than the elderly because their bodies are very active and still growing.
BLOOD PRESSURE
Is the pressure of the circulating blood against the walls of the blood vesels.
A sphygmomanometer: is the instrument used to measure blood pressure.
Blood pressure is measured by considering the systolic pressure and the diastolic pressure.
It is measured in millimeters of mercury (mmHg).
Adult blood pressure is considered normal at 120/80mmHg where the first number is the systolic pressure and the second number is the diastolic pressure.
QUESTION: Why a person’s blood pressure is recorded in two numbers?
Answer: Because when the heart beats once, the blood pressure rises to the maximum level and then fall to a minimum level.
The maximum blood pressure is called systolic pressure
The minimum blood pressure is called diastolic pressure
SYSTOLE
Is the phase occurs when the ventricles contract and pump blood into the arteries.
Systolic Pressure
Is the blood pressure which causes blood from contracting ventricles to flow into pulmonary artery and aorta.
DIASTOLE
Is the phase when the auricles contract to pump blood into the ventricles.
Diastolic Pressure
Is the blood pressure which causes blood from contracting auricles to flow into ventricles.
DISEASES AND DISORDERS OF THE HUMAN CIRCULATORY SYSTEM
The following are common diseases and disorders of the human circulatory system;
i. High blood pressure (hypertension)
ii. Leukemia
iii. Stroke
iv. Sickle cell anaemia
v. Arteriosclerosis
vi. Coronary thrombosis (heart attack)
HYPERTENSION (HIGH BLOOD PRESSURE)
Refers to a rise in blood pressure above the normal levels.
Causes of hypertension
i. High fat levels due to over-consumption of fatty foods.
ii. Lack of physical exercise.
iii. Obesity
iv. High emotional stress
v. Alcoholism and smoking
vi. Arteriosclerosis.
Signs and symptoms of hypertension
i. The signs and symptoms of hypertension include:
ii. Feeling dizzy
iii. Ringing sound in the ear.
iv. Severe headaches.
(iv) Aching of the body.
Prevention and treatment of hypertension
i. Hypertension can be prevented by:
ii. Eating a balanced diet with less fat
iii. Engaging in regular physical exercises
iv. Avoiding alcohol and smoking
v. Reducing stress.
vi. To control weight.
v. Hypertension can be treated using drugs.
LEUKEMIA
Is a type of blood cancer caused by the over production of white blood cells and the suppressed production of red blood cells.
ARTERIOSCLEROSIS
Is the hardening of arteries happen when fat deposits on the wall of the artery.
Causes of arteriosclerosis
i. Excessive alcohol and smoking.
ii. Stress.
iii. Too much fat in the diet.
iv. Lack of exercise or old age.
v. Hardening of arteries also happens when fibrous tissues form in the artery wall or artery.
SICKLE-CELL ANAEMIA
Is a genetic disorder which causes production of abnormal haemoglobin and malformed red blood cells.
The disease gets its name from the sickle shape or crescent shape of the red blood cells.
STROKE
This occurs when there is interference in the amount of blood flowing to the brain.
Causes of stroke
Interferences due to blockage or rupture of an artery supplying blood to the brain. Cause some brain cells to lack adequate oxygen and nutrients. Leading to difficulties in movement and coordination.
CORONARY THROMBOSIS (HEART ATTACK)
This occurs when there are blood clots in the blood vessels that supply blood to the heart.
This prevents blood from reaching some tissues of the heart. The affected tissues lack adequate amounts of oxygen and waste materials accumulate in the cells to toxic levels.
THE LYMPHATIC SYSTEM
Is part of the circulatory system made up of lymph fluid, lymph vessels, lymphoid organs and tissues.
COMPONENTS OF LYMPHATIC SYTEM
Lymphatic system is made up o the following components:
i. Lymph
ii. Lymph vessels
iii. Lymph nodes
iv. Associated tissues and organs such as tonsils, spleen, thymus.
LYMPH
Is a clear and colourless diluted blood plasma containing a large number of white blood cells, particularly lymphocytes.
Lymph is formed from tissue fluid that does not flow back into the capillaries.
It is formed by a process known as ultra filtration.
Function of lymph
Transports antibodies and white blood cells.
LYMPH VESSELS
Are thin tubes in the body through which lymph flows.
The lymph vessels have valves to prevent back flow of lymph and allow lymph to travel in one direction only.
Function of lymph vessel
Carries lymph fluid from body tissues to blood.
LYMPH NODES
Are nodule-like structures (swelling) formed in the lymphatic vessels.
They receive and filter lymph which contains unwanted materials.
Functions of lymph nodes
1. They help in defense against diseases.
2. They kill pathogens contained in it and release it to be transported back to the circulatory system.
3. Lymph nodes are important sites for the production of white blood cells.
4. They filter out foreign materials such as bacteria and dead tissue before they enter the bloodstream.
Various types of lymph nodes
(i) Inguinal lymph nodes-nodes found in the groin
(ii) Axillary lymph node- nodes found in the armpit.
(iii)Cervical lymph nodes- nodes in the neck.
(iv) Mesenteric lymph nodes- nodes found in the abdomen
TONSILS
Are found at the back of the throat.
Function of tonsils
They protect the body against infection by trapping pathogens entering through the mouth or the nose.
THE SPLEEN
Is the largest lymphatic organ.
Function of spleen
It also contains lymphocytes which kill pathogens.
Destroy dead tissues and any foreign substances.
THE THYMUS
Is located in the chest just above the heart.
— It stores immature lymphocytes and prepare them to become active T-cells which fight infections.
IMPORTANCE OF THE LYMPHATIC SYSTEM
1. It helps in production of lymphocytes (white blood cells).
2. The spleen destroys worn out red blood cells.
3. Lacteals enable absorption of fatty acids after digestion.
4. Collecting excess lymph fluid from body tissues and returning it to the blood.
5. It produces antibodies e.g. spleen, adenoids and tonsils.
DISORDERS AND DISEASES OF THE LYMPHATIC SYSTEM
There are many diseases and disorders that affect the lymphatic system. Some of these diseases and disorders include:
i. Elephantiasis
ii. Oedema
iii. Lymphoma
iv. Tonsillitis
1) ELEPHANTIASIS
Is an infection of the lymphatic vessels which causes a thickening of the skin and enlargement of underlying tissues, especially the legs and genitals.
— It is caused by parasitic worms called
filariae that block the lymph vessels causing accumulation of lymph which leads to swelling of the arms or legs.
Ways of transmission of elephantiasis
— Filariae infect the lymphatic system through bites by female mosquitoes called culexfor mosquitoes
Symptoms
— The parasite may live for 6 up to 8 years without showing any symptoms.
— Chronic elephantiasis is characterized by the following symptoms:
— Swelling of limbs
— Thickening of skin or tissue
— Accumulation of fluid in the swollen limb.
Effects
Elephantiasis causes deformation of limb.
A person fails to work hence increase life hardships.
Control and prevention measures of elephantiasis
1 Destroying the breeding areas of mosquitoes, for instance bushes and stagnant water.
2 Medication which kills and removes filarial parasites in the blood
3 Use of mosquito sprays and wire mesh on the window.
4 Personal hygiene is important for people with elephantiasis.
OEDEMA
This is the swelling of body tissues due to excessive lymph.
Causes of oedema
1 Increased blood pressure in the capillaries, causing the production of large amounts of lymph that the lymphatic system cannot transport efficiently,
2 Pregnancy,
3 Obesity and
4 Protein deficiency.
2) LYMPHOMA
Is the term used to refer to cancers that affect the lymphatic system.
— These cancers cause abnormal growth or functioning of the components of the lymphatic system.
— The result is weakened immune response in the body.
3) TONSILLITIS
This is an infection and swelling of the tonsils.
— It is caused by bacteria or viruses that enter the body through the mouth or sinuses.
TRANSPORT OF MATERIALS IN PLANTS
In plants, materials such as water, mineral salts and food are transported through a system of specialized tubes called a transport system.
The system is also called the vascular system.
VASCULAR SYSTEM
Is the system that involves transport of materials in plants.
The main materials that are transported in plants are water, mineral salts and manufactured food.
COMPONENTS OF THE VASCULAR SYSTEM
The transport system in plants is made up of tissues called vascular bundles, these are:-
i. Xylem
ii Phloem
iii. Vascular bundles are found in roots, stems and leaves
iv. Vascular bundles are made up of Xylem and Phloem which are separated by a wall called cambium
XYLEM
Is a tissue that transports water and mineral salts from the roots to the leaves through xylem vessels.
COMPONENTS OF XYLEM
i. Xylem is made up of the following components:
ii. Xylem vessels
iii. Tracheids elements
XYLEM VESSELS
Are long hollow tubes made of dead cells placed end to end.
Their walls are thickened with lignin to prevent them from collapsing as water is transported up the plant.
They are very efficient in transport of water and mineral and salts.
TRACHEID ELEMENTS
Are modified xylem cells with lignified pitted walls.
Tracheid elements are elongated with tapering ends and are made of dead cells.
They are less efficient in conduction of water and mineral salts.
PHLOEM
Is a tissue which transports manufactured food materials from the leaves to the rest parts of the plants.
Phloem is made up of living cells.
The cells are arranged to form long tubes with separating walls in between.
COMPONENTS OF PHLOEM
i. Phloem comprises the following components:
ii. Sieve tube elements.
iii. Companion cells.
SIEVE TUBE ELEMENTS
Are elongated cells that have end walls perforated by numerous minute holes allow dissolved materials to pass.
Sieve tube elements have companion cells separated by a thin wall made up of parenchyma cells with pores called plasmodeasmata
Function of plasmodeasmata
To allow exchange of materials between companion cells.
COMPANION CELLS
These cells work in association with sieve tubes.
They have many mitochondria to release energy for transporting food from the leaves to all parts of the plant.
Function of companion cells
To provide the sieve tube with energy required for translocation.
TRANSLOCATION
Is the movement of manufactured food substances in plant.
Translocation occurs in the phloem tissues.
Phloem and xylem are termed as muscular tissues.
IMPORTANCE OF THE TRANSPORT SYSTEM IN PLANTS
Plants need a transport system for:-
(i) Absorbing and transporting water which is required for photosynthesis
(ii) Transporting mineral salts needed for proper growth of plants.
(iii)Transporting manufactured food.
(iv) Removing excess water.
DISTRIBUTION OF VASCULAR BUNDLES IN PLANTS
Vascular bundles are arranged differently in the roots, stems and leaves.
MONOCOTYLEDONOUS ROOT
The vascular bundles in monocotyledonous root are arranged in ring form.
Monocot root have pith.
THE CROSS-SECTION DIAGRAM OF MONOCOT ROOT
• Dicot root have no pith
THE CROSS SECTION DIAGRAM OF DICOT ROOT
MONOCOTYLEDONOUS STEM
The vascular bundles in monocot stem are arranged random.
THE CROSS SECTION DIAGRAM OF MONOCOT STEM
DICOTYLEDONOUS STEM
The vascular bundles are arranged in a ring form (around central pith).
THE CROSS SECTION DIAGRAM OF DICOT STEM
ABSOPTION AND MOVEMENT OF WATER AND MINERAL SALTS
Absorption of water and mineral salts from the soil to the plant body is performed by root hair.
ROOT HAIRS
Are structures which involve in absorption of water and mineral salts from the soil.
FUNCTION OF ROOT HAIRS
Increase surface area for water and mineral salts absorption in plants.
ADAPTION OF A ROOT HAIR TO ITS FUNCTION
1. Root hairs are long and slender to provide a large surface area for the absorption of water and mineral salts from the soil.
2. Root hairs they are large in number to increases the surface area for absorption of water and mineral salts.
3. The root hair cell sap is usually hypertonic to the surrounding to allow water enters the cell by osmosis.
4. The root hairs are very thin in order to provide a short distance over which absorption of water and mineral salts takes place.
FORCES WHICH CAUSE A CONTINUOUS FLOW OF WATER IN THE XYLEM
The following are forces which cause a continuous flow of water in xylem
i. Transpiration pull
ii. Cohesion
iii. Adhesion
iv. Capillarity
v. Root pressure
TRANSPIRATIONAL PULL
Is a tension that draws water upward from the root to the leaf.
The tension can cause continous loss of water from plant by transpiration forces.
TRANSPIRATION STREAM
Is a continuous column of water from the roots to the leaves through the xylem.
CAPILLARITY
Is the tendency of water to rise in very narrow tubes
Xylem vessels and tracheids have very narrow lumen which enables water to rise in them by capillarity.
NB: Capillarity is made possible by cohesion and adhesion forces.
COHESION
Is the force of attraction between similar molecules
Water molecules are cohesive hence stick to each other.
ADHESION
Is the force of attraction between different molecules.
Water molecules adhere to the wall of xylem vessels.
Cohesion and adhesion forces maintain a continuous column of water in xylem vessels from the roots to the leaves of plants.
ROOT PRESSURE
Is the force that pushes water absorbed from the soil to move up the stem
This happens because the cells of the endodermis push mineral into the xylem.
This increases osmotic pressure in the xylem thereby creating a force that moves the water and dissolved minerals up the xylem vessel.
TRANSPIRATION
Is the process by which plants lose water through the stomata in the leaves.
Transpiration mainly occurs in the stomata.
TYPES OF TRANSPIRATION
i. Stomatal transpiration ii. Cuticular transpiration
iii. Lenticular transpiration
I. STOMATAL TRANSPIRATION
Is a type of transpiration in which water lose occurs through the stomata on the leaves.
It accounts for approximately 90% of the water lost by plants.
CUTICULAR TRANSPIRATION
Is the transpiration in which water lose occur through the cuticle of the leaves.
NB: Excessive loss of water in plant is prevented by a thick cuticle
LENTICULAR TRANSPIRATION
Is the transpiration that takes place through the lenticels.
Topic 4: Transportation Of Minerals Of Living Things – Biology Notes Form 2
FACTORS AFFECTING THE RATE OF TRANSPIRATION
Factors affecting the rate of transpiration are grouped into two namely:
i. Structural factors (plant features)
ii. Environmental factors.
STRUCTURAL FACTORS
The following are structural factors affecting the rate of transpiration
1. NUMBER OF STOMATA
The more stomata a leaf have, the faster the rate of transpiration and vice versa.
2. THE SIZE AND SHAPE OF LEAVES.
Plants with large leaves lose more water than those with smaller leaves since large leaves have more stomata than small leaves.
3. AN EXTENSIVE ROOT SYSTEM
Plants that have extensive roots absorb more water hence lose more water than those with few roots.
4. LEAF CUTICLE
A thick cuticle resists water loss by transpiration while a thin cuticle makes water loss by transpiration easier.
5. POSITION OF STOMATA
The rate of transpiration is faster in plant with more stomata on the upper surface of a leaf than those with more stomata on the lower surface of a leaf.
6. SIZE OF SUB STOMATAL AIR SPACES
Larger air spaces allow for a faster rate of transpiration because the leaves can hold more water vapor. Smaller substomatal air spaces slow down the rate of transpiration.
7. SUNKEN STOMATA
Sunken stomata occur in pits. They are not exposed to moving air so they slow down transpiration rate.
8. EPIDERMAL HAIRS
Epidermal hairs trap water on the surface of the leaves, thus preventing water loss
ENVIRONMENTAL FACTORS
The rate of transpiration is also affected by the following environment factors
1. TEMPERATURE
Transpiration rates increases as the temperature increases.
Higher temperatures cause the stomata to open and release water into the atmosphere.
2. RELATIVE HUMIDITY
The transpiration rate falls when the relative humidity of the surrounding air rises.
It is easier for water to evaporate into dry air than into air saturated with moisture.
3. WIND AND AIR MOVEMENT
Increased movement of the air around a plant results in a higher transpiration rate.
4. LIGHT INTENSITY
Higher light intensity increases the rate of transpiration.
5. AVAILABILITY OF SOIL MOISTURE
The rate of transpiration decreases with decreases of the soil moisture.
When moisture is lacking in the soil, plants begin to age prematurely resulting in leaf loss and reduced transpiration. Also, less water is absorbed by the roots when the soil is dry.
6. ATMOSPHERIC PRESSURE
The rate of transpiration increases with decreases of atmospheric pressure.
SIGNIFICANCE OF TRANSPIRATION
1. Transpiration helps to cool the plants.
2. Transpiration helps to maintain transpiration pull.
3. Transpiration helps plant to loss excess water.
4. Transpiration helps in the water cycle.
5. Transpiration helps plant to absorb and distribute water and mineral salts.
6. Transpiration helps plant in gaseous exchange and removal of waste products
DISADVANTAGES OF TRANSPIRATION
1. Transpiration causes wilt of plants due to excessive loss of water.
2. Transpiration creates water loss which may make the land a desert.
3. Transpiration produces poison when plant is removing the excess minerals.
GUTTATION
Is the process through which plants lose water in form of liquid droplets.
DIFFERENCES BETWEEN GUTATION AND TRANSPIRATION
| GUTTATION | TRANSPIRATION |
| Water is lost in form of droplets | Water is lost in form of vapouraq. |
| Occurs during the night. | Occurs during the day. |
| Occurs through the hydathodes. | Occurs through the stomata, cuticle or lenticels. |
EXAMINATION QUESTIONS
1. Explain what will happen if the barks of shoot root or stem removed.
ANSWER
The plant will wilt due to the removal of xylem vessels in the barks which transport water and mineral salts.
