Unofficial AQA Biology Unit 3 GCSE NEW SPEC Mark Scheme

1.

Coronary Artery [1]

2.

Stents [1]

3.

Stents are metal mesh tubes inserted into blood vessels to expand them if they are blocked, for example by fatty deposits or cholesterol. They are placed in surgery using an inflated balloon. It increases the blood vessel size at the blockage to allow blood to flow more effectively. [2]

1.

Coronary Artery [1]

2.

Coronary Bypass Surgery [1]

3.

The heart is stopped in surgery. The narrowed section of coronary artery is cut and removed from the surface of the heart. Then, another section of blood vessel, usually from the groin, is cut out and the two ends of the vessel stitched back up. The section of vessel is then taken to the location on the heart and stitched onto the coronary artery. The heart is restarted and the blood should effectively. [2]
.

4.

Artery [1]
Capillary [1]
Vein [1]
.

5.

The blood in the artery is de-oxygenated (without oxygen) while the blood in the vein is oxygenated (with oxygen). [1]

1.

There is a slow increase in lung volume in the first 1.2 seconds. The volume peaks at 4.8 cubic dm. Then, there is a slow gradual decrease in pressure for the next 1.2 seconds. [3]

2.

When breathing in, the following occurs: the intercostal muscles contract, the ribcage expands, the diaphragm flattens, volume of thorax increases, pressure of thorax decreases and air is drawn in. This is shown by the increase and peak in the graph. The opposite is true (intercostal muscles relax and ribcage contracts) when breathing out, shown by the decrease in the graph. [3]

3.

Positive pressure ventilation systems force air into the lung, changing the pressure inside the lung. While, negative pressure systems change the pressure outside the lung, forcing air in and out. [2]

4.

An advantage of the positive pressure ventilator is that it does not interrupt the air flow in the lungs whereas in negative pressure it does. Positive pressure systems can, also, be digitally controlled and aid in muscle building. A disadvantage of positive pressure is that the alveoli can burst if it cannot handle the pressure. This can happen in small children or babies. [2]

1.

The second food chain (wheat→pigs→humans) has more steps and wastes more energy because the pigs use energy in respiration for movement, homoeostasis, etc. The first food chain (wheat→human) provides ten times more energy than the second food chain. [2]
.

2.

Factory farming is when food production is made more efficient by reducing energy loss and maximising growth.

Animals are kept in a small space or cage which reduces land requirements. This provides more space for other crops or resources and, so, more food is produced in a smaller space. This is more profitable and creates a larger yield or more produce. However, it is easier for animals to catch diseases off one another and it is expensive to monitor diseases.

Animals' movement is, also, restricted. This reduces energy loss by movement and creates full-size animals quickly. This is more profitable and creates a larger yield or more produce. However, it is seen as cruel, unethical and inhumane as it restricts the animals' freedom- against animal rights. Moreover, stressed animals gain weight less quickly then non-stressed animals.

Moreover, animals are kept warm and indoors. Therefore, less energy is expended by the animal on heating itself, homoeostasis. More energy is used for growth. This quickens the growing process and more profit in the long-term. But, it can be expensive to heat the animals and causes an indirect CO2 increase as fuels are burnt to produce heat energy. [6]

1.

(310-210)/(180-30) = 2/3 = 0.6 (Recurring) [2]

2.

Between 0-30 seconds, there was an increased rate of evaporation causing a higher water loss while between 30-180 seconds the rate of evaporation steadily decreased causing a lower water loss- this altered the rate of transpiration between the two time periods. The rate of evaporation may have altered due to change in the environment, closing of stomata or some other factor. [2]

3.

Osmosis is used by roots as there is a higher concentration of water in soil than in root, uptake is along the concentration gradient. Active transport is used as there is a higher concentration of ions in roots than in the soil, uptake is against the concentration gradient. [4]

4.

The transpiration stream is the flow of water from the root to the leaves through the xylem. It is due to water loss in the leaves, leading to low concentration of water in the leaves and high concentration of water in the roots. [3]

1.

Oxygen [1] Allow Mineral Ions

2.

Surface X allows exchange of food and gas which is difficult in complex organisms. As the tadpole grows, Surface X increases in surface area. This increases the surface area:volume ratio of the tadpole. Therefore, there is more area from diffusion to occur. It, also, means that gases, such as oxygen, and other dissolved substances, such as mineral ions, can diffuse in and out quickly which is important for the tadpole to survive. [4]

1.

When the body get too hot, the blood vessels dilate (vasodilation) to reduce body temperature and lose more heat. When the body gets too cold, the blood vessels contract (vasoconstriction) to increase body temperature and reduce heat loss. [4]

2.

The athlete overheats as there is reduced or no evaporation of sweat, which occurs slowest in humid conditions. This is due to reduced gradient or saturation or high water content of the (humid) air. Also, there is less heat loss by the (latent) heat of evaporation [3]

1.

The person has just had a meal. Therefore, the hepatic portal vein has contains a high level of blood sugar. Insulin is produced by the pancreas and this converts the glucose into glycogen, which is stored in the liver. Therefore, the hepatic vein contains less glucose and has a lower blood sugar level. [3]

2.

The hepatic portal vein has contains a low level of blood sugar. The body requires a constant level of blood sugar. Glycogen is produced to convert glycogen, stored in the liver, into glucose. Therefore, the hepatic vein contains more glucose than the hepatic portal vein and has a higher blood sugar level. [3]

3.

The graph decreased as transpiration in the plant stopped since the leaf had no roots for the uptake of water. Therefore, no more water was taken in by the leaf for photosynthesis. [1]