Transport System – SS2 Biology Lesson Note (Second Term)

Transportation is the movement of metabolic materials from the parts of an organism where they are produced to other parts where they are used, stored or removed from the body.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Define transportation and state why living organisms need a transport system.
2. Compare transport in lower organisms with transport in higher organisms.
3. List the materials transported in animals and plants, with their sources and destinations.
4. Name the transport media in organisms.
5. Describe the composition of blood and the functions of the blood cells and plasma.
6. State the functions of blood.

Why do living organisms need a transport system?

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

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

How does transport in lower organisms compare with transport in higher organisms?

What materials are transported in animals?

What materials are transported in plants?

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

What are the transport media in organisms?

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

1. Cytoplasm: Used in lower unicellular organisms such as amoeba, chlamydomonas, euglena, etc.
2. Cell sap or latex: A concentrated solution in the cell vacuole of plants.
3. Blood: Used in most animals, especially vertebrates, for conveyance of essential materials like oxygen, digested food, etc.
4. Lymph: Found in higher animals. It is a fluid with extra lymphocytes (white blood cells), and no red blood cells are present.

What is lymph and how does it move?

Lymph returns its fluid to the main vein through an opening in the subclavian (left jugular) vein below the neck. Lacteal is a lymphatic vessel transporting fatty acids and glycerol. Lymph moves through lymph vessels, and its movement is enhanced by muscular action.

Some swellings exist in the body along the lymphatic vessels, especially in the neck, groin and armpit. They are called lymph nodes. Lymph passes through them to be purified before entering the bloodstream. Unlike the circulatory system, the lymphatic system ends blindly.

How are materials transported in different organisms?

Unicellular organisms

Materials are transported through 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 organisms

Hydra

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

Flatworms

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

Insects and molluscs

Both have an open circulatory system. 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 flow is unidirectional and blood distribution is poorly controlled.

What is the transport system in mammals (man)?

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

What is the composition and structure of blood?

The blood is a tissue in a fluid form. It is about 5 to 6 litres in the body. Blood is made of two major components: the blood cells (corpuscles), which are solid, and the plasma, which is liquid.

What are the types of blood cells?

There are three types:

1. Red blood cells (erythrocytes)
2. White blood cells (leucocytes)
3. Blood platelets (thrombocytes)

White blood cells are of two types:

1. Phagocytes: found in the lymphatic system. They ingest bacteria, viruses and dead cells to prevent diseases, in a process called phagocytosis.
2. Lymphocytes: made in lymph glands. They produce antibodies, which are chemicals that stick to the surface of germs to kill them.

What are the functions of blood?

1. Oxygen is transported through haemoglobin.
2. Temperature regulation by evenly distributing heat produced in the liver and the muscles throughout the body.
3. Transportation of digested food (glucose, amino acids, fatty acids and glycerol) from the villi to all body cells and tissues for use or storage.
4. Transportation of excretory products (CO₂, water, urea) from the site of production to excretory organs like skin, lungs, liver and kidney for removal.
5. Transfer of hormones from the production site to target organs.
6. Transportation of water (90% of the blood content) to various cells for metabolic activities.
7. Defence against infection through the action of WBC.
8. Blood clotting, which is initiated by the platelets when an injury is sustained.
9. Production of antibodies by the WBC for destroying pathogens and their harmful products.

Evaluation

1. Define transportation.
2. State four reasons why living organisms need a transport system.
3. State three differences between transport in lower organisms and transport in higher organisms.
4. Name the three types of blood cells and state one function of each.
5. State four functions of blood.

Assignment

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