Transport in Animals

What Transport in Animals covers

Transport in animals is the second section of Module 3. It covers single and double circulation, the structure of arteries, veins and capillaries, how tissue fluid forms and returns, the mammalian heart and the cardiac cycle, the electrocardiogram, and how blood carries oxygen and carbon dioxide.

The 8 subtopics

Each one has its own page.

• Why animals need transport systemsSize, metabolic rate and surface area to volume ratio, and the difference between single and double, open and closed circulatory systems.Open →
• Arteries, veins and capillariesWall structure, lumen size, valves and the amount of elastic and muscle tissue in each vessel, and how each one suits the pressure it carries.Open →
• Tissue fluid and lymphHydrostatic and oncotic pressure at each end of a capillary, how tissue fluid forms and returns, and how plasma, tissue fluid and lymph differ.Open →
• The structure of the mammalian heartThe four chambers and the vessels entering and leaving them, the valves, chordae tendineae and papillary muscles, and why the left ventricle wall is thicker.Open →
• The cardiac cycle and control of the heartbeatAtrial systole, ventricular systole and diastole, what opens and closes the valves, the cardiac output calculation, and the route from sino-atrial node to Purkyne tissue.Open →
• The electrocardiogramWhat the P wave, QRS complex and T wave represent, and how tachycardia, bradycardia, fibrillation and an ectopic beat appear on a trace.Open →
• Transporting oxygen and carbon dioxideThe quaternary structure of haemoglobin and cooperative binding, and the three ways carbon dioxide travels, including carbonic anhydrase and the chloride shift.Open →
• Oxygen dissociation curves and the Bohr effectWhy the curve is sigmoid, how fetal haemoglobin differs from adult haemoglobin, and the shift the Bohr effect produces and what it achieves in respiring tissue.Open →

What you need to know

Answer each one before you reveal it.

Take Transport in Animals further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Single circulation vs Double circulation

  Single circulation: blood passes through the heart once during each complete circuit. Double circulation: blood passes through the heart twice during each complete circuit.

• Artery vs Vein

  Artery: vessel carrying blood away from the heart under relatively high pressure. Vein: vessel returning blood towards the heart under relatively low pressure.

Questions from this topic

Each one with the model answer underneath.

1. 1

   Why does a large body size in multicellular animals necessitate a transport system rather than relying on diffusion alone?

   Model answer

   Large body size increases the diffusion distance, making diffusion too slow to supply nutrients and remove waste efficiently across the organism.

2. 2

   How does a high metabolic rate contribute to the need for a transport system in multicellular animals?

   Model answer

   A high metabolic rate increases the demand for nutrients and oxygen, and produces more waste, which diffusion alone cannot supply or remove quickly enough.

3. 3

   Why does a low surface area to volume ratio make diffusion insufficient for exchange in large animals?

   Model answer

   A low SA:V ratio means the exchange surface is small relative to the volume of tissue requiring supply, so diffusion cannot meet the metabolic demands of all cells.

4. 4

   Explain why the surface area to volume ratio decreases as an organism increases in size.

   Model answer

   Volume increases as the cube of linear dimensions while surface area increases only as the square, so volume grows faster than surface area.

5. 5

   What defines a single circulatory system?

   Model answer

   Blood passes through the heart once per complete circuit of the body.

6. 6

   What defines a double circulatory system?

   Model answer

   Blood passes through the heart twice per complete circuit, with separate pulmonary and systemic circulations.

What is inside Levo

Six ways to work the same material.

Transport in Animals revision questions

What does Transport in Animals cover in OCR A-Level Biology?

8 subtopics: why animals need transport systems, arteries, veins and capillaries, tissue fluid and lymph, the structure of the mammalian heart, the cardiac cycle and control of the heartbeat, the electrocardiogram, transporting oxygen and carbon dioxide and oxygen dissociation curves and the bohr effect. Each one has its own page with questions and model answers.

How is Transport in Animals organised?

By the OCR H420 specification, subtopic by subtopic, so it matches the order you are taught it in.