The shape of the lesson
By the end of the lesson, learners can
- Pump, vessels and valves: Switch the sim between the fish and the mammal and watch the blood cells change colour as they travel.
- Single and double circulation: Extended.
- Circulatory system: blood vessels + a pump + valves for one-way flow.
- Single (fish): heart → gills → body → heart; once through the heart.
- Double (mammal): pulmonary circuit to the lungs, systemic circuit to the body; twice through the heart.
- Advantage: say high pressure to the body, so faster delivery of oxygen and glucose.
One picture every idea returns to
The circulatory system is a system of blood vessels with a pump (the heart) and valves that ensure a one-way flow of blood. Extended: a fish has a single circulation, in which blood passes through the heart once in each complete circuit of the body. A mammal has a double circulation: blood passes through the heart twice in each circuit, once on the way to the lungs and once on the way to the rest of the body.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, A pump, pipes and one-way valves.. Every cell in a large animal needs oxygen and glucose delivered and its waste carried away, faster than diffusion alone could manage. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Pump, vessels and valves | Switch the sim between the fish and the mammal and watch the blood cells change colour as they travel. Project tab 1 of the lab (Single and double circulation) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Single and double circulation | Extended. | Rally Robin |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 18 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Single and double circulation, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Rally Robin
Pairs take turns to say one item each, back and forth: a definition, a unit, a step of the method. Keep it fast and oral; the point is retrieval, not writing.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| A circulatory system is not just "the heart and blood". | The syllabus description has three parts: blood vessels, a pump, and valves to ensure one-way flow. Name all three. |
| "Twice through the heart" is a description, not an advantage. | For an explain the advantages question, say what the second pumping achieves: higher pressure, faster delivery of oxygen and glucose to respiring cells. |
Circulatory systems: worksheet
6 questions, 18 marks. Written in the style of the papers; no past paper question is reproduced.
Describe what is meant by a circulatory system.
Extended. Describe the route taken by blood in the single circulation of a fish, starting at the heart.
Extended. Describe the double circulation of a mammal.
Extended. Explain the advantages of a double circulation for an active mammal.
Extended. The table shows the blood pressure in two vessels of a fish.
| Vessel | Blood pressure / kPa |
|---|---|
| artery leaving the heart, before the gills | 4.0 |
| artery leaving the gills, going to the body | 2.4 |
(a) Calculate the percentage fall in pressure across the gills. (b) Explain how a double circulation avoids this problem in a mammal.
Explain why valves are needed in a circulatory system.
Answer key and marking notes
- A system of blood vessels (arteries, capillaries and veins)...
- ...with a pump, the heart, which pushes the blood round...
- ...and valves, which ensure the blood flows in one direction only.
- The heart pumps deoxygenated blood to the gills.
- In the gills the blood takes up oxygen and becomes oxygenated.
- The blood flows from the gills to the body organs, then returns to the heart: it passes through the heart once per circuit.
- The right side of the heart pumps deoxygenated blood to the lungs (the pulmonary circulation).
- Oxygenated blood returns from the lungs to the left side of the heart.
- The left side pumps the oxygenated blood to the rest of the body (the systemic circulation), and deoxygenated blood returns to the right side.
- So the blood passes through the heart twice in each complete circuit.
- Blood returning from the lungs is pumped again, so it reaches the body at high pressure and flows quickly.
- Oxygen and glucose are delivered rapidly to respiring cells, supporting a high metabolic rate (activity and keeping warm).
- Blood goes to the lungs at lower pressure, so the delicate lung capillaries are not damaged; and oxygenated and deoxygenated blood are kept separate.
- (a) Fall = 4.0 − 2.4 = 1.6 kPa; (1.6 ÷ 4.0) × 100 = 40%.
- (b) In a mammal, blood from the lungs returns to the heart (left side) instead of going straight to the body.
- It is pumped a second time, so its pressure is raised again before it goes to the body organs.
- Valves close when blood starts to flow backwards.
- This keeps the blood flowing in one direction, so it is pushed on round the circuit rather than back towards the heart or into the chamber it came from.
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which three things together make up a circulatory system?
- ABlood vessels, a pump and valves
- BBlood, lungs and a pump
- CArteries, veins and the lungs
- DA pump, a septum and the kidneys
What is the function of the valves in the circulatory system?
- ATo make sure blood flows in one direction only
- BTo pump blood out of the heart into the arteries
- CTo let oxygen diffuse out of the blood into the tissues
- DTo mix oxygenated and deoxygenated blood together
A small, flat worm has no circulatory system, but a large earthworm has one. What is the best explanation?
- AIn a large animal diffusion alone is too slow to supply cells far from the surface
- BSmall animals do not need oxygen, so they need no transport system
- CLarge animals have more cells, so each cell needs less oxygen
- DFlat worms make all the glucose their cells need by photosynthesis
(Extended) The diagram shows the circulation of a fish. Which vessel carries oxygenated blood?
- AX, from organ P to organ Q
- BW, from the heart to organ P
- CY, from organ Q to the heart
- DNone, as fish blood never carries oxygen
(Extended) How many times does blood pass through the heart in one complete circuit of the body in a mammal and in a fish?
- AMammal twice, fish once
- BMammal once, fish twice
- CMammal twice, fish twice
- DMammal once, fish once
In a mammal, which side of the heart pumps blood into the pulmonary circulation, and to where?
- AThe right side, to the lungs
- BThe left side, to the lungs
- CThe right side, to the body organs
- DThe left side, to the body organs
A student says: "Blood in a mammal goes from the heart to the lungs and then straight on to the body." What is wrong with this?
- ABlood returns to the heart after the lungs before going to the body
- BBlood goes to the body first and only then to the lungs
- CBlood goes from the heart to the gills, not the lungs
- DBlood never passes through the lungs in a mammal
(Extended) Birds and mammals both have a double circulation and keep a constant high body temperature. Why is a double circulation an advantage to these animals?
- AHigh pressure to the body delivers oxygen and glucose fast for a high respiration rate
- BBlood travels more slowly, so it has more time to warm up
- CLess oxygen reaches the tissues, so less heat is produced
- DBlood flows through the gills twice, collecting more oxygen
Quiz key
A circulatory system is a system of blood vessels with a pump (the heart) and valves that ensure a one-way flow of blood. Blood is what is carried, not part of the description, and the lungs are gas exchange organs supplied by the system. Arteries and veins are vessels, but the lungs are not part of the system's definition. The septum is one part of the heart and the kidneys are excretory organs.
Valves close when blood starts to flow backwards, so blood moves in one direction only. Pumping is done by the heart muscle contracting, not by the valves. Diffusion into tissues happens through capillary walls. Keeping oxygenated and deoxygenated blood apart is the job of the septum, and mixing them would be a disadvantage.
In a large animal many cells are far from the surface, and diffusion over long distances is too slow to supply them, so a pump and vessels are needed to carry substances quickly. In a thin, flat animal every cell is close to the surface. All animals need oxygen for respiration, more cells do not reduce each cell's needs, and animals cannot photosynthesise.
In a fish the heart pumps deoxygenated blood to the gills (P), where it takes up oxygen. Vessel X carries this oxygenated blood on to the body organs (Q). Vessel W carries deoxygenated blood from the heart to the gills, and Y returns deoxygenated blood from the body to the heart. Fish blood does carry oxygen; it collects it in the gills.
A mammal has a double circulation: blood goes heart, lungs, heart, body, heart, so it passes through the heart twice per circuit. A fish has a single circulation: heart, gills, body, heart, so once. The other answers swap or merge the two systems.
The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs: the pulmonary circulation. The left side pumps oxygenated blood to the body organs, which is the systemic circulation. The other options mix up the sides or the destinations.
In a mammal blood returns from the lungs to the left side of the heart and is pumped again to the body, so it does not go straight on. The student has described a single circulation like a fish's. Leaving the heart, blood from the right side goes to the lungs first, not the body. Gills belong to fish, and mammal blood must pass through the lungs to collect oxygen.
Blood is pumped a second time after the lungs, so it reaches the body at high pressure and flows quickly. Oxygen and glucose are delivered fast enough to support a high rate of respiration, releasing the energy needed for activity and to keep warm. A double circulation speeds blood up rather than slowing it, it increases oxygen delivery rather than reducing it, and birds and mammals have lungs, not gills.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.