TYS 2019

Question 1

Suggest the purpose of microvilli in the small intestine [2]

Answer 1

Microvilli increases surface area to volume ratio of villi of the small intestine;
To increase absorption of digested food molecules at a faster rate into the blood stream of the villi;

Question 2

Suggest the effects on the body of having a hole in the heart [2]

Answer 2

The hole in the wall between the two atria will result in mixing of deoxygenated blood in the right atrium with the oxygenated blood in the left atrium;
Resulting in insufficient/ lesser amount of oxygen transported to other organs and cells; decreasing the rate of respiration and lesser energy released for cellular activities;

Question 3

Explain how water moves out of the leaf from the xylem to the atmosphere. [5]

Answer 3

Water molecules enter the leaf from xylem, due to transpiration pull;
net movement of water molecules from the cells surrounding xylem to the adjacent mesophyll cells, down a water potential gradient by osmosis;
Water molecules move out of the mesophyll cells to form a thin film of moisture lining the surface of the mesophyll cells which evaporates to form water vapour in the intercellular air spaces;
Water vapour diffuses from the intercellular air spaces out of the leaf through the stomata into the atmospheric air/ atmosphere;
Down a water vapour concentration gradient during transpiration;

Question 4

Explain why having stomata open in daylight is an advantage to plants. [4]

Answer 4

Gaseous exchange can take place, carbon dioxide can diffuse into the leaf via opened stomata for increased photosynthesis rate [1]
Oxygen can also diffuse out of the leaf [1]
Water vapour can diffuse out of the leaf and this help to cool the plant down as it helps removes latent heat [1]
The open stomata would allow the transpiration stream/pull to deliver water to be used in photosynthesis and maintain of cell turgor [1]

Question 5

Discuss two social and two ethical implications of using chickens to produce human proteins [4]

Answer 5

Social issues:
* This method of production could potentially reduce cost of medicine for consumers, making
it more affordable
* The new proteins in chicken might cause allergy in human when consumed Altered gene to produce human protein in chicken eggs may be toxic or cancer-causing to people
who consume it.
* May lead to class distinction where only individual with financial means can afford such
GM proteins as medication.
Ethical issues:
* Some people may find it morally wrong to exploit chickens for medical research in genetic engineering
* Vegans and vegetarians may find it offensive to consume genes from animal source in these type of medicine.

Question 6

Suggest why having a large proportion of fish in the sea that are 40cm is a good indicator. [3]

Answer 6

Having more fishes that are 40 cm and longer indicates that more fishes are in the adult stage and hence are larger; [1]
Reflects that fishes are able to survive and reproduce, thus increasing population size; [1]
It also indicates a large population of secondary and tertiary consumers; [1]
This indirectly shows that there are sufficient food in the ocean ecosystem to support a larger population of high trophic level consumers; [1]