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Module 2 Exchange and transport 1.2.5 Transport in animals Learning Objectives • Explain the need for transport systems in multicellular animals in terms of size, activity and surface-area-to-volume ratio. • Explain the meaning of the terms single and double circulatory systems with reference to the circulatory systems of fish and mammals Success Criteria • List the features of a good transport system (Grade E - D) • Explain why large, active animals need a transport system (Grade C –B) • Explain why a double circulatory system is more efficient than a single circulatory system (Grade B – A) FISH DISSECTION? Closed circulatory systems Why need a transport system? Single-celled organisms, such as bacteria and amoeba (below), can obtain nutrients and excrete waste simply by diffusion. nutrients waste products Multi-cellular organisms, such as insects, fish and mammals, require a more specialized transport system. Why is this? 4 of 33 © Boardworks Ltd 2008 Surface area to volume ratio In larger organisms, diffusion of substances would occur far too slowly to enable them to survive: This is not just because of its size, however: more important is an organism’s surface area to volume ratio. Single-celled organisms have a very large surface area to volume ratio, because the diffusion path is so short. Describe 3 factors that would affect the need for transport systems.. •List the features of a good transport system 5 of 33 (Grade E ©-Boardworks D) Ltd 2008 1 Size 1)If an animal has several layers of cells, any oxygen and nutrients will not reach the deeper cells within the body •Explain why large, active animals need a transport system (Grade C –B) 2 Surface Area to Volume Ratio • Larger animals have a small surface-areavolume-ratio. • Larger volume due to range of tissues. • Their surface area is not large enough to supply all the oxygen and nutrients needed by internal cells. 3 Level of Activity • If an animal is active it will require a good supply of oxygen and nutrients to supply the energy for movement. • Mammals also require more energy to keep themselves warm. Features of a good transport system Division of labour Our circulatory system has 2 loops- one sends blood to the lungs-pulmonary system and the other sends blood to the rest of the body – systemic system. Features of a good transport system • • • • • Medium/fluid to carry nutrients and oxygen Pump to create pressure Exchange surface Vessels/tubes to contain medium 2 circuits – Pick up oxygen – Deliver oxygen Closed circulatory systems Advantages of Double over Single • Double circulatory system – blood travels through the heart twice for each complete circuit of the body • Efficient so deliver nutrients quickly • Can increase pressure of blood flow • Quicker supply oxygen • Can keep pressure to exchange surface low to avoid damage Plenary: True or False 1. Mammals are more active that fish due to need to maintain body temperature 2. Surface area to volume ratio effects need for a transport system 3. Single circulatory system means a single chambered heart 4. Systemic circulation means the route of blood through the lungs 5. Surface area to volume ratio is effected by an animals shape Plenary: True or False 1. Mammals are more active that fish due to need to maintain body temperature 2. Surface area to volume ratio effects need for a transport system 3. Single circulatory system means a single chambered heart 4. Systemic circulation means the route of blood through the lungs 5. Surface area to volume ratio is effected by an animals’ shape • Any answers you wrote false for now please write what the true statement would be Plenary: Answers 1. Mammals are more active that fish due to need to maintain body temperature • True 2. Surface area to volume ratio effects need for a transport system • True 3. Single circulatory system means a single chambered heart] • False: Single circulatory system means blood does one circuit 4. Systemic circulation means the route of blood through the lungs • False: Systemic circulatory system means the route of blood through the body 5. Surface area to volume ratio is effected by an animals’ shape • True