Biology by Bradford
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The subtopic in the middle and 14 tasks round it: label seven diagrams, complete two tables, put two processes in order and fill 74 gaps. Every standard level statement has a box; the seven boxes for higher level only are dashed and badged HL, and drop off for an SL class. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
Fatty builds up in the wall of a coronary artery and narrows it. A blood forming there can block it completely, so the heart muscle beyond is starved of and dies: a heart attack. Country data like these give r = 0.8, a strong correlation, but a correlation alone cannot prove .
The vascular bundles lie in a near the outside of the stem. In each, the outer tissue carries and the inner one carries and mineral ions.
| Artery | Vein | |
|---|---|---|
| Blood pressure | low | |
| Wall | thick layers of muscle and tissue | thin and flexible |
| Keeping blood moving | the stretched wall between beats, keeping the pressure up | stop backflow; nearby muscles squeeze the vein |
Each surge that stretches an artery is a pulse. Press two fingertips on the artery at the wrist or the artery in the neck, count for 15 s and multiply by to give beats per minute.
Number the steps in order.
Water molecules hold on to one another by , so the column does not break.
The smallest vessels branch into dense beds of narrow tubes with a huge . Their wall is thick, and some have pores, , where exchange must be very fast.
Xylem vessels are dead tubes with no cell contents and no , so water flows through unimpeded. Their walls are thickened with , so they do not collapse under , and water moves in and out sideways through .
In a root the vascular tissue sits in the , not in a ring of bundles.
At the arteriole end of a capillary, high blood pressure forces plasma out through the wall: . This tissue fluid has the small solutes of plasma but almost no , which are too large to leave. Cells take O₂ and glucose from it and pass CO₂ and wastes into it. At the end the pressure is lower, so most of it drains back in. The excess enters ducts, whose thin walls have gaps and whose keep it flowing back towards the blood.
Sugars are loaded into the phloem at a , such as a leaf, and unloaded at a , such as a root or fruit. When transpiration is too slow, roots pump mineral ions into the xylem by ; water follows by osmosis, building a positive .
123| Bony fish | Mammal | |
|---|---|---|
| Route of the blood | heart → → body → heart | heart → → heart → body → heart |
| Times through the heart in one circuit | once | |
| Pressure of blood reaching the body | high |
So a fish has a single circulation and a mammal a one.
The keeps oxygenated and deoxygenated blood apart. The walls are , fed by the , and each beat starts at the heart's own .
Number the steps in order.
In a blood pressure of 120/80 mmHg, 120 is the pressure, as the ventricles contract, and 80 the pressure, as they relax.
1234The smallest vessels branch into dense beds of narrow tubes with a huge surface area. Their wall is one cell thick, and some have pores, fenestrations, where exchange must be very fast.
| Artery | Vein | |
|---|---|---|
| Blood pressure | high | low |
| Wall | thick layers of muscle and elastic tissue | thin and flexible |
| Keeping blood moving | the stretched wall recoils between beats, keeping the pressure up | valves stop backflow; nearby muscles squeeze the vein |
Each surge that stretches an artery is a pulse. Press two fingertips on the radial artery at the wrist or the carotid artery in the neck, count for 15 s and multiply by 4 to give beats per minute.
Fatty plaque builds up in the wall of a coronary artery and narrows it. A blood clot forming there can block it completely, so the heart muscle beyond is starved of oxygen and dies: a heart attack. Country data like these give r = 0.8, a strong positive correlation, but a correlation alone cannot prove causation.
Water molecules hold on to one another by cohesion, so the column does not break.
Xylem vessels are dead tubes with no cell contents and no end walls, so water flows through unimpeded. Their walls are thickened with lignin, so they do not collapse under tension, and water moves in and out sideways through pits.
The vascular bundles lie in a ring near the outside of the stem. In each, the outer tissue carries sugars and the inner one carries water and mineral ions.
In a root the vascular tissue sits in the centre, not in a ring of bundles.
At the arteriole end of a capillary, high blood pressure forces plasma out through the wall: pressure filtration. This tissue fluid has the small solutes of plasma but almost no proteins, which are too large to leave. Cells take O₂ and glucose from it and pass CO₂ and wastes into it. At the venule end the pressure is lower, so most of it drains back in. The excess enters lymph ducts, whose thin walls have gaps and whose valves keep it flowing back towards the blood.
| Bony fish | Mammal | |
|---|---|---|
| Route of the blood | heart → gills → body → heart | heart → lungs → heart → body → heart |
| Times through the heart in one circuit | once | twice |
| Pressure of blood reaching the body | low | high |
So a fish has a single circulation and a mammal a double one.
The septum keeps oxygenated and deoxygenated blood apart. The walls are cardiac muscle, fed by the coronary arteries, and each beat starts at the heart's own pacemaker.
In a blood pressure of 120/80 mmHg, 120 is the systolic pressure, as the ventricles contract, and 80 the diastolic pressure, as they relax.
Sugars are loaded into the phloem at a source, such as a leaf, and unloaded at a sink, such as a root or fruit. When transpiration is too slow, roots pump mineral ions into the xylem by active transport; water follows by osmosis, building a positive root pressure.