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?

A transport system is needed to carry materials to and from every cell of a plant or animal.

• Supply of materials: to obtain essential materials such as oxygen, water and nutrients.
• Removal of waste: to remove metabolic waste such as carbon dioxide, urea and water.
• Water and mineral salts in plants: to move them from the soil through the roots to the various parts of the plant.
• Hormones: to carry them from the place where they are produced to the place where they act.
• Glucose in plants: to carry it to the various parts of the plant.

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

Lower organisms are small and simple, such as amoeba and hydra, so materials move by diffusion over short distances.

Higher organisms are large and complex, such as mammals and flowering plants, so they need a transport system to move materials over long distances.

What materials are transported in animals?

Animals transport gases, food substances, waste products, hormones and antibodies between organs and body cells.

What materials are transported in plants?

Plants transport manufactured food, waste gases, water and mineral salts between leaves, stems and roots.

What other materials are transported in plants?

• Oxygen: needed by living cells for respiration.
• Nitrogen waste products (latex): milky fluid carried in some plants, such as rubber.
• Amino acids: building blocks of protein.
• Glucose: sugar used for energy or stored.
• Lipids: fats and oils for storage.
• Auxins (hormones): plant hormones that control growth.
• Mineral salts: absorbed from the soil.

What are the transport media in organisms?

Transport media are the fluids that carry materials in an organism, and there are four major ones: cytoplasm, cell sap or latex, blood and lymph.

• Cytoplasm: used in lower unicellular organisms such as amoeba, chlamydomonas and euglena.
• Cell sap or latex: a concentrated solution in the cell vacuole of plants.
• Blood: used in most animals, especially vertebrates, to carry oxygen, digested food and other essential materials.
• Lymph: found in higher animals, it is a fluid with extra lymphocytes (white blood cells) and no red blood cells.

What is lymph and how does it move?

Lymph is a colourless fluid in the lymphatic system, with a composition similar to tissue fluid but with extra lymphocytes.

• Movement: lymph moves through lymph vessels, helped by the action of muscles.
• Return to the blood: lymph drains back into the blood through the subclavian veins near the base of the neck.
• Lacteal: a lymphatic vessel in a villus that carries fatty acids and glycerol.
• Lymph nodes: swellings along the lymph vessels, especially in the neck, groin and armpit.
• Purification: lymph passes through the nodes to be cleaned before it enters the bloodstream.
• Blind ending: unlike the circulatory system, the lymphatic system ends blindly.
• Defence: disease-causing microorganisms in lymph are held in the nodes and engulfed by phagocytes.

How are materials transported in different organisms?

The method of transport depends on the size and structure of the organism.

How are materials transported in unicellular organisms?

Unicellular organisms transport materials by continuous streaming movements of the cytoplasm.

• Amoeba: the cytoplasm streams along the direction of movement, from back to front.
• Paramecium: the cytoplasm streams in a circular motion.

How are materials transported in multicellular organisms?

Hydra

• Movement of the gut wall draws water into the gut.
• This makes digested food and oxygen in the gut circulate.
• The cells lining the gut absorb the materials.
• The whipping movement of flagella on flagellated cells also helps circulation in the gut.

Flatworms

• The large surface area to volume ratio lets food and oxygen diffuse into the body cells.
• An extensive branching gut runs throughout the body and carries food close to all cells.
• Movement of the body wall helps to move waste products out of the body.

Insects and molluscs

• Insects and most molluscs (such as snails) have an open circulatory system.
• The heart pumps blood into a blood vessel whose branches open into body spaces called haemocoels.
• Blood from these spaces flows back into vessels that lead to the heart.
• Blood flows in one direction, but its distribution is poorly controlled.

What is the difference between open and closed circulatory systems?

In an open circulatory system, blood leaves the vessels and bathes the tissues in body spaces called haemocoels.

In a closed circulatory system, blood stays inside vessels all the time.

What is the transport system in mammals (man)?

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

What is the composition and structure of blood?

Blood is a tissue in fluid form, and an adult has about 5 to 6 litres of it.

• Blood cells (corpuscles): the solid part of blood.
• Plasma: the liquid part of blood.

What are the types of blood cells?

There are three types of blood cells: red blood cells, white blood cells and platelets.

• Red blood cells (erythrocytes): carry oxygen.
• White blood cells (leucocytes): defend the body against disease.
• Blood platelets (thrombocytes): help blood to clot.

What are the types of white blood cells?

There are two types of white blood cells: phagocytes and lymphocytes.

• Phagocytes: found in the blood and the lymphatic system, they ingest bacteria, viruses and dead cells in a process called phagocytosis.
• Lymphocytes: made in the lymph glands, they produce antibodies, which are chemicals that attach to germs and help to destroy them.

What is blood plasma?

Blood plasma is the pale yellow liquid part of blood, made up of about 90% water.

• Dissolved substances: plasma proteins, antibodies, hormones, enzymes, gases, digested food, salts and waste products.
• Function: it transports the dissolved substances and the blood cells.

What is the difference between blood and lymph?

Blood is the red fluid pumped by the heart through blood vessels, and it contains red cells, white cells and platelets.

Lymph is a colourless fluid in the lymph vessels, with no red cells and extra lymphocytes.

What are the functions of blood?

Blood transports materials, protects the body against infection and helps to regulate body temperature.

1. Oxygen transport: oxygen is carried by haemoglobin in the red blood cells.
2. Temperature regulation: blood spreads heat from the liver and muscles evenly through the body.
3. Transport of digested food: glucose, amino acids, fatty acids and glycerol go from the villi to all body cells for use or storage.
4. Transport of excretory products: CO₂, water and urea go to excretory organs such as the skin, lungs, liver and kidney.
5. Transfer of hormones: hormones go from the production site to the target organs.
6. Transport of water: water, which makes up about 90% of the plasma, goes to cells for metabolic activities.
7. Defence against infection: white blood cells engulf pathogens.
8. Blood clotting: platelets start clotting when an injury occurs.
9. Production of antibodies: white blood cells make antibodies that destroy 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

Answer all five questions in your exercise book.

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 blood components has a nucleus:
   A. red blood cell
   B. white blood cells
   C. platelets
   D. plasma