CGS 2021 Flashcards
The woman is infertile. With reference to Fig. 1.1 (collapsed oviduct wall), explain why this is so. [2] (CGS 2021)
- The oviduct is blocked/ occluded/ sealed/ closed off [1]
- Fertilisation cannot occur as ovum cannot be moved to meet/ fuse with the sperm due to the blocked oviduct. [1]
A woman’s progesterone levels rise after day 14 and peak around day 24. Suggest and explain a time range during the menstrual cycle when implantation would be likely to be most successful. [3] (CGS 2021)
- Between day 21-24; [1]
- Progesterone functions to maintain the thickness of the uterine lining; [1]
- During this period, progesterone level is increasing towards peak, indicating uterine lining is most likely the thickest. [1]
Explain one way in which the structure of the villus is adapted for its function. [2] (CGS 2021)
ANY one of below
- Epithelium of the villus have numerous microvilli; [1] to increase surface area to volume ratio for faster absorption of digested
food [1].
- Epithelium/ wall of villus is one cell thick [1] to reduce diffusion distance for faster absorption of digested food [1].
- Contains a lacteal which continually
transports fats away from ileum [1] to maintain a steep concentration gradient for faster absorption of fats [1].
- Well-supplied with blood capillaries which continually transports digested food away from duodenum [1] to maintain a steep concentration gradient for faster absorption
of digested food [1].
Adults who suffer from coeliac disease are easily fatigued.
With reference to Fig. 2.1 and Fig. 2.2, explain how coeliac disease can cause fatigue in adults. [2] (CGS 2021)
The villi in person with coeliac disease is shorter, thus has smaller surface area to volume ratio [1].
Less glucose absorbed into bloodstream, resulting in less respiration, releasing less energy, hence causing fatigue [1]
Toxic chemicals from the soil slow down the rate of respiration. Plants that absorb these toxic chemicals do not grow as well as those growing in toxin-free soils.
Explain why. [3] (CGS 2021)
- When the rate of respiration slows down, less energy is released resulting in less active transport [1].
Less active transport results in less translocation of sucrose and amino acids from leaves to the rest of the plant for growth [1]. - Less respiration results in less energy for cell activities such as photosynthesis to produce
glucose, reducing plant growth [1]. - Less mineral ions absorbed/ ions absorbed more slowly at the roots by active transport [1]. Less nitrate ions causes less amino acids/ protein results in less protoplasm/ growth;[1]
Explain why transpiration rate increased when the plant was placed next to the fan. [3] (CGS 2021)
The wind blows away the water vapour that accumulates outside the leaf. [1]
This causes a steeper water vapour
concentration gradient between the inside of the leaf and the atmosphere. [1]
This allows water vapour to diffuse out of the leaf faster [1], increasing rate of transpiration.
Explain how wilting reduces the rate of transpiration. [1] (CGS 2021)
The leaf folds up, reducing exposed surface area to reduce rate of transpiration OR
stomata closes, reducing rate of
transpiration. [1]
Describe two ways in which a flower is adapted for pollination by the bee. [2] (CGS 2021)
Has a large and conspicuous petal [1]
Non-pendulous anther and compact stamen; [1]
Non-feathery and compact stigma; [1]
The bee visited this flower after leaving another flower of the same plant.
Identify the type of pollination involved.[1]
Self-pollination
Species P relies on cross-pollination.
Describe two ways in which flowers from species P may be adapted to increase the likelihood of pollination. [2]
Any [2]
· Plants bear either male or female
flowers.
· Anthers and stigmas in the same plant mature at different times.
· Stigmas are situated far away from the anthers in the same plant.
· Pollen grains of a flower have no
fertilizing effect on the stigmas of the same plant.
The average concentration factor of urea in urine of a healthy individual is x 60.0.
Suggest an explanation for the difference in his concentration factor of urea in urine from that of a healthy individual. [2]
High protein diet/ protein-rich diet/ meals [1]
Higher amount of/ More excess amino acids are deaminated to produce more urea [1]
(i rejected low water intake as it only specifies urea.)
When the blood clot blocks the vessel in the lungs, it would eventually lead to the death of the cells in the lungs. Explain why. [2]
Less/ No oxygen will be transported to these cells and cells will undergo less/ no aerobic respiration [1]
Less/ No energy is released for cellular activities [1]
Explain how the lipid coating on capsules ensures that the enzymes are not released until the capsule reaches the small intestine. [2]
There is no lipase produced / found [1] in stomach / mouth / before small intestine [1]
OR
Lipase only produced / found [1] in the by epithelial cells / intestinal juice in the small intestine [1]
In an experimental set-up, a plant is watered with water radioactively labelled with isotope 18O. The plant is then placed in a sealed chamber and the radioactivity of 18O in the chamber is measured over time.
Explain the change in radioactivity in the chamber as shown in Table 8.1. [4]
- Radioactive water (R: solution) enters root hair cell by osmosis and transported upwards in xylem; [1]
- Moves out of xylem to mesophyll cells; [1]
[Photosynthesis] Radioactive water used for photosynthesis (R: water is photolysed) ; [1]
Radioactive oxygen gas produced and
diffuses out of leaves; [1]
OR
[Transpiration] Thin film of moisture around spongy mesophyll evaporates; [1]
Radioactive water vapour diffuses out of leaves [1]
Compare and contrast between the process of mitosis and meiosis. [4]
Similarities (at least [1])
· Both involve nuclear division
· Both form / produce new daughter cells
· Both involve prophase, metaphase,
anaphase and telophase
R: both involve metaphase/ only one parent
cell/ centrioles/ doubling of chromosome number
differences:
- number of nuclear divisions
- number and type of daughter cells (diploid/haploid)
- genetically identical?
- crossing over of alleles?
- occurs in?
- pairing of homologous chromosomes?
- independent assortment?`
