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Transport system is the movement of metabolic materials from various parts of an organism where they are produced and transported to other parts where such are used, stored or removed from the body.

Need For Transport System

All living organisms (plants and animals) need transport system for the following reasons

  • To obtain essential materials such as oxygen, water and nutrients.
  • To remove metabolic waste such as carbon dioxide, urea, water, etc.
  • For moving water and mineral salts from the soil through the roots to the various parts of plant.
  • For transfer of hormones from production site to site of action.
  • For transfer of glucose to various parts of plants.


  Transport in Lower Organisms Transport in Higher Organisms
1 Substances are moved over small distance  Substances are moved over greater distance
2 Transport is by simple diffusion Transport involves diffusion and other means.
3 Diffusion is enough because the surface area to volume ratio (A/V) is great Effusion transport system is necessary because surface area to volume ratio (A/V) is too small
4 Cells are not isolated Isolated group of cells need to be connected
5 Transport materials are small in quantity. Transport materials are large in quantity.


  1. What is transport system?
  2. State the needs for transport system.

Transport Materials In Animals

Materials Transported Source Destination
1 Oxygen Lungs All living cells of the body
2 Carbon dioxide Body cells Lungs
3 Urea Body cells Liver
4 Excess salts Body cells Skin and kidney
5 Water Body cell Skin, lungs, liver, kidney etc
6 Amino acid Small intestine Body cells
7 Vitamins Small intestine Body cells
8 Sugar Body cells Body cells
9 Fatty acid and glycerol Small intestine Body cells
10 Mineral salt Small intestine Body cells
11 Hormones Endocrine glands Target organs of tissue
12 Antibodies White blood cells All body parts

Transport Materials in Plants

Materials Transported Source Destination
Manufactured food Leaves All body cells
Excretory Products       (C02 and water) All living cells Site of excretion e.g. stomata
Water (absorbed) Soil Leaves and other parts of the leaves

Other materials transported in plants are:

  1. Oxygen 2.nitrogen waste products (latex) 3. amino acids 4. glucose 5. lipids 6. auxins (hormones) 7.mineral salts

Transport Media

Liquid or fluid is usually the medium of transportation of minerals. Generally speaking, the four major media of transportation in organisms are:

Cytoplasm: Used in lower unicellular organisms such as amoeba, chlamydomonas, euglena, etc.

Cell sap/ Latex: A concentrated solution in the cell vacuole of plants.

Blood: Used in most animals, especially vertebrates for conveyance of essential materials like oxygen, digested food, etc.

Lymph:  Found in higher animals. Lymph is a fluid with extra lymphocytes (W.B.C with no red blood cells present). It returns its fluid to the main vein through opening in the subclavian (left jugular) vein below the neck.Lacteal is a lymphatic vessel transporting fatty acids and glycerol. The lymph movement is enhanced by muscular action. It moves through lymph vessel. Some swellings exist in the gut along the lymphatic vessel, especially in the neck, groin and armpit called lymph nodes. These are where lymph passes through to be purified before entering into the blood stream. Unlike the circulatory system, the lymphatic system ends blindly.


  1. Mention two differences between the lymphatic system and the circulatory system.
  2. List transport materials common to both plants and animals

Diverse Mechanisms of Transportation in Some Organisms

Unicellular Organisms

Materials are transported through the continuous streaming movements. The streaming could be along the direction of movement of the organism, back to front (e.g. Amoeba) or in circular motion (e.g. Paramecium)

 Multicellular Organism

  1. Hydra

The movement of the gut wall draws water into the gut and causes digested food and oxygen within it to circulate. Thus the cell lining the gut absorbs the materials. The whopping movement of the flagella of flagellated cells also helps in material circulation in the gut.

  1. Flatworms

The large body surface area to volume ratio and extensive branching gut throughout the body makes the food and oxygen to diffuse into all the body cells. Movement of the body wall assists to transport waste products out of the body.

  1. Insects and mollusks

Both have open circulatory system i.e. the heart pumps blood out into a blood vessel with branches open into spaces in the body cavity known as Haemocoels. Blood from these spaces eventually flows into the vessels leading into the heart. Blood flows in unidirectional and blood distribution is poorly controlled.


The media of transportation in man include the blood and lymph.


The blood is a tissue in a fluid form. It is about 5-6 liters in the body. Blood is made of two major components.The blood cells (corpuscles); which are solid.The plasma which; is liquid.


 transport system


There are three types

  • Red blood cells (erythrocyte)
  • White blood cells (leucocytes)
  • Blood platelets (thrombocytes)
Blood Cells Description Function
RBC 1.      Small, round and disc-like in shape

2.      Has no nucleus.

3.      One cubic liter of blood has about 5.5million of red blood cells.

4.      Has a life span about 120 days

Helps to transport oxygen from lungs to the body cells through its pigment (haemoglobin). Haemoglobin combines readily with oxygen to form oxyhaemoglobin in the lungs
WBC 1.      Irregular (i.e. amoeboid in shaped)

2.      Relatively large and colourless (larger than RBC but fewer)

3.      Contain nucleus- about 5,000-10,000 per pin head of blood (cubic milliliter of blood)

Help to defend the body against diseases by engulfing and intruding pathogens (bacteria and virus) or by secreting antibodies.

RBC- Red Blood Cell                               WBC- White Blood Cell

 White blood cells are of two types;

Phagocytes- found in lymphatic system which ingest bacteria, viruses and dead cells to prevent diseases in a process called phagocytosis.

Lymphocytes– made in lymph glands and they produce antibodies i.e. chemicals which stick to the surface of germs to kill them.

transport system2

Blood cell Description Function
Platelets 1.      Tiny, Irregular all fragments

2.      Have no nucleus

3.      Fewer in number and smaller in size than RBC.

4.       About 250,000 – 400,000 per cubic ml of blood.

5.      Produced in red bone marrow.

Aids in blood clotting
Blood plasma

(transport liquid)

1.      Liquid component of blood

2.      A pale yellow liquid made up mainly of water (about 90% water) together with other dissolved substances like plasma proteins antibodies, hormones, enzymes, gases, digested food, salts and other waste products

Transport the dissolved substances and the blood cells.
Lymph 1.      A colourless liquid in lymphatic system that has similar composition to the tissue fluid but contains extra lymphocytes.

2.      Has no red cell

·       Body defense by producing white blood cells. Disease causing micro organisms found in the lymph are pushed out in the lymph node and engulfed by phagocytes.

·       Absorption of fatty acid and glycerol


  1. Oxygen is transported through hemoglobin.
  2. Temperature regulation by evenly distributing heat produced in the liver and the muscles throughout the body.
  3. Transportation of digested food (glucose, amino acid, fatty acids and glycerol) from the villi to all body cells and tissues for use or storage.
  4. Transportation of excretory products (C02, water, urea) from site of production to excretory organs like skin, lungs, liver and kidney for removal
  5. Transfer of hormones from production site to target organs.
  6. Transportation of water (90% of the blood content) to various cells for metabolic activities.
  7. Defense against infection through the action of WBC
  8. Blood clotting initiated by the platelets when injury is sustained
  9. Production of anti bodies by the WBC for destroying pathogens and their harmful product.


  1. State the media for transportation in ten organisms.
  2. Compare the transport mechanism of a named unicellular organism to that of a named multi-cellular organism
  3. Draw the diagram of RBC, WBC and platelets (label them accordingly)
  4. What feature distinguishes lymph from blood plasma?
  5. State five functions of blood.



  1. The following are true except one about transport in amoeba
  2. substances are removed over greater distance B. transport is by simple diffusion C. diffusion is enough for transport D. substances are moved over short distance
  3. The following metabolic materials are transported from body cells to the skin and kidney A.sugar B. hormones C. excess salt D. protein
  1. The transport medium which plays active roles in the defense and metabolism of lipids is … A. cytoplasm B. lymph C. blood D. platelets
  2. The following animals except one has open circulatory system
  3. goat B. house fly C. snail D. grasshopper.
  4. One of the following has nucleus
  5. red blood cell B. white blood cells C. platelets D. hydra


  1. (a) Why is blood a tissue? (b) Differentiate between blood and lymph.
  2. Describe the transport system in a named mollusk.

See also






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