2023 HKDSE Biology Practice Paper | DSE Mock

Which of the following processes in a flowering plant directly requires the expenditure of metabolic energy (ATP)?

I. Transport of sucrose into sieve tubes.
II. Movement of water across the root cortex.
III. Uptake of mineral ions by root hair cells from a dilute soil solution.

In an experiment, a plant is supplied with water containing \(^{18}\text{O}\) and carbon dioxide containing \(^{16}\text{O}\). Which of the following substances will contain \(^{18}\text{O}\) after a period of active photosynthesis?

During the opening of stomata in daylight, which of the following events occur in the guard cells?

I. Active transport of potassium ions (\(\text{K}^+\)) into the guard cells.
II. An increase in the water potential of the guard cells.
III. Water enters the guard cells by osmosis, causing them to become turgid.

Which of the following statements about ecological pyramids is/are correct?

I. A pyramid of energy can never be inverted.
II. A pyramid of numbers must always be upright.
III. A pyramid of biomass can be inverted in marine ecosystems where producers have a very high turnover rate.

In waterlogged and poorly aerated soil, which of the following processes in the nitrogen cycle is promoted, leading to a reduction in soil fertility?

In a certain species of mice, yellow coat color is dominant to grey coat color. When two yellow mice are crossed, they always produce yellow and grey offspring in a \(2:1\) ratio. When a yellow mouse is crossed with a grey mouse, they produce yellow and grey offspring in a \(1:1\) ratio. Which of the following is the most likely explanation?

A plant with genotype \(AaBb\) is test-crossed with a plant of genotype \(aabb\). The offspring exhibit the following numbers for each phenotype:
- Phenotype AB: 42
- Phenotype Ab: 8
- Phenotype aB: 12
- Phenotype ab: 38

Which of the following is the most likely explanation for these results?

Which of the following combinations correctly matches the digestive secretion, its site of production, and its digestive function?

Most carbon dioxide is transported in the human blood in the form of hydrogencarbonate ions (\(\text{HCO}_3^-\)). Which of the following events occur inside red blood cells to facilitate this transport?

I. Carbon dioxide reacts with water to form carbonic acid, catalyzed by carbonic anhydrase.
II. Hydrogencarbonate ions diffuse out of the red blood cells into the plasma.
III. Chloride ions diffuse into the red blood cells to maintain electrical neutrality.

Which of the following is a key difference between blood plasma and tissue fluid in a healthy human?

A leafy shoot is attached to a bubble potometer to study the rate of transpiration under identical environmental conditions. The following results were obtained: (1) Untreated shoot: rate of bubble movement = 10 mm/min; (2) Upper epidermis of all leaves coated with vaseline: rate = 8 mm/min; (3) Lower epidermis of all leaves coated with vaseline: rate = 3 mm/min; (4) Both upper and lower epidermis coated with vaseline: rate = 1 mm/min. What is the ratio of stomatal transpiration from the upper epidermis to that from the lower epidermis?

A plant is grown in a well-aerated nutrient solution. Which of the following treatments would significantly decrease the rate of uptake of phosphate ions by the root hair cells? (1) Bubbling nitrogen gas instead of air into the solution; (2) Adding a respiratory inhibitor to the solution; (3) Increasing the light intensity on the leaves.

A ring-barking (girdling) experiment is conducted on the stem of a woody plant, removing a ring of tissues external to the xylem. After several weeks, which of the following is most likely to be observed?

In some marine ecosystems, the pyramid of biomass is inverted (i.e., the biomass of primary consumers is larger than that of primary producers), while the pyramid of energy remains upright. Which of the following best explains this observation?

The diagram below outlines part of the nitrogen cycle in an ecosystem: Atmospheric nitrogen -> Process W -> Ammonium ions -> Process X -> Nitrate ions -> Process Y -> Atmospheric nitrogen. Which of the following statements about these processes is correct?

During primary ecological succession on bare rock, which of the following trends is typically observed as the community progresses towards a climax community?

In humans, a rare genetic disorder is controlled by a single gene with two alleles. An unaffected couple has three children: an affected daughter, an unaffected son, and an affected son. Based on this pedigree information, which of the following is correct?

In a plant species, seed shape is controlled by gene A (A: round, a: wrinkled) and seed color is controlled by gene B (B: yellow, b: green). A plant with the genotype AaBb is self-crossed. Assuming the two genes assort independently, what is the probability that an offspring will have the same phenotype as the parent plant?

Which of the following substances absorbed in the human small intestine is transported into the villus epithelial cells primarily by simple diffusion?

Two hours after a human consumed a meal rich in carbohydrates, blood samples were collected from the hepatic portal vein and the hepatic vein. Which of the following statements correctly compares the blood in these two vessels?

Which of the following statements about the symplastic pathway of water transport in plant roots is correct?

Which of the following statements about pyramids of biomass and pyramids of energy is correct?

A healthy couple has a daughter who suffers from a genetic disorder controlled by a single gene. Which of the following modes of inheritance is/are definitely ruled out? (1) Autosomal dominant, (2) X-linked dominant, (3) X-linked recessive

A student set up four test tubes to study the digestion of lipids. Tube 1: 2 mL lipid emulsion + 1 mL pancreatic juice + 1 mL bile salt solution at 37 °C; Tube 2: 2 mL lipid emulsion + 1 mL boiled pancreatic juice + 1 mL bile salt solution at 37 °C; Tube 3: 2 mL lipid emulsion + 1 mL pancreatic juice + 1 mL distilled water at 37 °C; Tube 4: 2 mL lipid emulsion + 1 mL pancreatic juice + 1 mL bile salt solution at 0 °C. In which tube will the pH decrease at the fastest rate?

A healthy volunteer drank 1 liter of pure water within 10 minutes. Which of the following changes would occur in the volunteer's body over the next hour?

During the light-dependent reactions of photosynthesis, water molecules are split. Which of the following correctly describes the products of this photolysis and their primary destination or role in the light-independent reactions?

A cell from an organism with a diploid chromosome number of \(2n = 8\) undergoes meiosis. At metaphase II, how many chromosomes and DNA molecules are present in a single cell?

A child accidentally steps on a rusty nail and is given an injection of anti-tetanus immunoglobulins (antibodies) at the hospital. Two weeks later, the child is exposed to the same tetanus toxin again. Which of the following statements is correct regarding the child's immunity?

A single base deletion occurs early in the coding sequence of a gene. What is the most likely consequence of this mutation on the resulting protein?

Under which of the following environmental conditions would a terrestrial herbaceous plant show the highest rate of transpiration?

A leafy shoot is connected to a potometer to measure water uptake. The setup is placed in a room with stable temperature and light intensity. Which of the following operations would lead to a decrease in the rate of movement of the air bubble? (1) Smearing vaseline on the lower surface of all leaves. (2) Enclosing the shoot in a clear plastic bag containing a small amount of water. (3) Turning on a fan directed towards the shoot.

A potted plant is supplied with carbon dioxide labeled with carbon-14 (\(^{14}\text{C}\)) under light. Which of the following represents the correct pathway of the \(^{14}\text{C}\) from the atmosphere to the storage site in the root?

The diagram below shows part of the nitrogen cycle in a forest soil: Organic nitrogen \(\xrightarrow{\text{Process 1}}\) Ammonium compounds \(\xrightarrow{\text{Process 2}}\) Nitrates \(\xrightarrow{\text{Process 3}}\) Nitrogen gas. Which of the following descriptions of the bacteria involved in these processes is correct?

In a family pedigree investigating a genetic disorder: Couple A (both normal) has an affected daughter. This affected daughter marries a normal man, and they have an affected son and a normal daughter. Based on this pedigree, which of the following statements must be correct? (1) The allele causing the disorder is recessive. (2) The disorder is autosomal. (3) The normal husband must be heterozygous.

Which of the following combinations correctly matches the nutrient, its main absorption site, and its transport route from the small intestine to the heart?

An unknown liquid sample is subjected to various food tests. The results are as follows: Test 1: Adding iodine solution \(\rightarrow\) Yellow-brown; Test 2: Heating with Benedict's reagent \(\rightarrow\) Blue; Test 3: Biuret test \(\rightarrow\) Purple; Test 4: Heating with Benedict's reagent after acid hydrolysis and neutralization \(\rightarrow\) Brick-red precipitate. Which of the following nutrients are present in the sample?

A herbaceous plant was treated with a chemical that selectively inhibits active transport in the root hair cells. Predict and explain the effect of this chemical on the rate of water uptake by the plant.

In an agricultural ecosystem, farmers practice intercropping by planting legumes alongside corn. Explain how this practice benefits both the nitrogen content of the soil and the growth of the corn plants without the use of synthetic nitrogen fertilizers.

A couple, Mr. and Mrs. Chan, both have normal vision. They have a daughter with normal vision and a son who has red-green color blindness (a sex-linked recessive trait). (a) With reference to the genotypes of the parents, explain why they can have a color-blind son. (3 marks) (b) State the probability that their next daughter will be a carrier of the color-blindness allele. (1 mark)

An experiment is set up using a potometer to measure the rate of water uptake of a leafy shoot. The shoot is exposed to different wind speeds (0 m/s and 3 m/s) at two different relative humidities (40% and 80%).

(a) Describe how the potometer should be set up to ensure accurate measurement of water uptake. (3 marks)

(b) Explain the effect of increasing wind speed from 0 m/s to 3 m/s on the rate of water uptake under low relative humidity (40%). (3 marks)

(c) Predict and explain how the effect of wind speed on water uptake would change if the experiment is repeated at high relative humidity (80%). (3 marks)

A student compared the stomatal density and distribution of two plant species: Lilium (a terrestrial plant) and Nymphaea (an aquatic floating plant with leaves resting on the water surface).

(a) Explain why the Nymphaea leaf has almost all of its stomata located on the upper epidermis, whereas the Lilium leaf has most of its stomata on the lower epidermis. (4 marks)

(b) If the Nymphaea plant is completely submerged under water due to flooding, describe how this would affect its rate of photosynthesis, and explain your answer in terms of carbon dioxide availability. (3 marks)

(c) Suggest one structural adaptation, other than stomatal distribution, that is typical of floating aquatic leaves to facilitate gas exchange. (2 marks)

Two areas, Area A (covered in solidified lava after a volcanic eruption) and Area B (abandoned agricultural land after a forest fire), undergo ecological succession.

(a) Identify the type of ecological succession occurring in Area A and Area B respectively, and explain the key difference between these two types in terms of the initial conditions of the soil. (3 marks)

(b) Lichens and mosses are typically the pioneer species in Area A. Explain how these pioneer species modify the environment to allow subsequent colonization by herbaceous plants. (3 marks)

(c) State three characteristics of a climax community that are different from those of the early stages of succession. (3 marks)

An ecological study of a grassland ecosystem was conducted. The energy contents at three trophic levels were measured: Primary Producers (\(8.4 \times 10^5\text{ kJ m}^{-2}\text{ yr}^{-1}\)), Primary Consumers (\(7.2 \times 10^4\text{ kJ m}^{-2}\text{ yr}^{-1}\)), and Secondary Consumers (\(5.4 \times 10^3\text{ kJ m}^{-2}\text{ yr}^{-1}\)).

(a) Calculate the ecological efficiency (transfer efficiency) from primary producers to primary consumers. Show your working. (2 marks)

(b) Explain why a large proportion of energy is lost as it flows from primary consumers to secondary consumers. Give three reasons. (3 marks)

(c) In some aquatic ecosystems, the pyramid of biomass at any one moment can be inverted (i.e., the biomass of primary consumers is larger than that of primary producers). Explain how this is possible despite the laws of thermodynamics. (3 marks)

The pedigree chart below shows the inheritance of a genetic disorder in a family:

- Generation I: I-1 (unaffected male) and I-2 (affected female).
- Generation II: They have three children: II-1 (affected female), II-2 (unaffected male), and II-3 (affected male). II-1 marries II-4 (affected male).
- Generation III: II-1 and II-4 have two children: III-1 (unaffected female) and III-2 (affected male).

(a) Based on the pedigree, deduce whether the allele for this disorder is dominant or recessive. Explain your deduction with reference to specific individuals. (4 marks)

(b) Deduce whether the gene is sex-linked or autosomal. Explain your answer with reference to specific individuals. (3 marks)

(c) If individual II-3 marries an unaffected woman, what is the probability that their first child will inherit the disorder? Explain your reasoning. (2 marks)

In tomato plants, the allele for tall stem (\(T\)) is dominant over dwarf stem (\(t\)), and the allele for red fruit (\(R\)) is dominant over yellow fruit (\(r\)). A homozygous tall, yellow-fruited tomato plant is crossed with a homozygous dwarf, red-fruited tomato plant to produce the F1 generation.

(a) State the phenotype and genotype of the F1 generation. (2 marks)

(b) An F1 plant is backcrossed with the dwarf, yellow-fruited parent (a test cross).

(i) Predict the phenotypic ratio of the offspring from this cross if the two genes assort independently. (2 marks)

(ii) If the actual cross resulted in a very high proportion of parental phenotypes (tall, yellow-fruited and dwarf, red-fruited) and a very low proportion of recombinant phenotypes (tall, red-fruited and dwarf, yellow-fruited), explain the genetic basis of this observation. (3 marks)

(c) State the biological process during meiosis that is responsible for producing the low proportion of recombinant phenotypes in (b)(ii). (1 mark)

A patient underwent a partial gastrectomy (removal of a portion of the stomach) and also has a blocked bile duct due to gallstones.

(a) Explain how a blocked bile duct would specifically affect the digestion of lipids in the small intestine. (3 marks)

(b) Patients with a blocked bile duct often produce feces that are pale in color and greasy/foul-smelling (steatorrhea). Explain the biological reasons for these two characteristics. (3 marks)

(c) State three structural adaptations of the ileum that maximize the rate of absorption of digested food substances. (3 marks)

Describe how the structural features of the stem and leaves of a terrestrial woody plant facilitate the transport of water and adaptation to survive in hot and dry environments. (11 marks)

Describe how the structural features of the stem and leaves of a terrestrial woody plant facilitate the transport of water and adaptation to survive in hot and dry environments. (11 marks)

A group of healthy volunteers participated in an exercise trial. They ran on a treadmill at a constant speed for 60 minutes under two different environmental conditions:\n\nCondition X: Hot and dry (\(35^\circ\text{C}\), relative humidity 20%)\nCondition Y: Hot and humid (\(35^\circ\text{C}\), relative humidity 85%)\n\n(a) Explain why the core body temperature of the volunteers rose faster in Condition Y than in Condition X, despite the air temperature being the same. (4 marks)\n\n(b) Explain why prolonged sweating leads to an increase in blood osmolarity and describe how the endocrine and urinary systems respond to restore blood osmolarity. (8 marks)\n\n(c) After the exercise in Condition X, the volunteers lost \(1.5\text{ kg}\) of body mass (mainly due to water loss).\n(i) If they only drink \(1.5\text{ L}\) of pure water immediately after the exercise, their urine production increases rapidly, and they fail to fully restore their body fluid volume. Explain this observation. (5 marks)\n(ii) Suggest why drinking an isotonic sports drink containing sodium ions is more effective in restoring fluid balance. (3 marks)

An ecological survey was conducted in a coastal bay in Hong Kong to investigate the impact of coastal reclamation and plastic pollution on the marine ecosystem, specifically focusing on a population of the Chinese White Dolphin (Sousa chinensis) and their primary prey, the croaker fish.\n\n(a) Coastal reclamation leads to habitat loss and fragmentation.\n(i) Explain how habitat fragmentation can affect the genetic diversity of the Chinese White Dolphin population over generations. (4 marks)\n(ii) Besides habitat loss, explain one other physical impact of reclamation on the marine environment that can negatively affect marine organisms. (3 marks)\n\n(b) Microplastics (\(< 5\text{ mm}\)) are abundant in the bay. Samples of seawater, croaker fish (prey), and tissue samples from stranded dolphins were analyzed for the concentration of a persistent organic pollutant (POP) called PCB, which adsorbs onto microplastics. The average concentration of PCBs (in ppm) was:\n- Seawater: \(0.0002\text{ ppm}\)\n- Croaker fish: \(1.5\text{ ppm}\)\n- Chinese White Dolphin: \(45.0\text{ ppm}\)\n\n(i) Describe and explain the phenomenon illustrated by the data above. (4 marks)\n(ii) Explain why microplastics pose a greater threat of chemical toxicity to marine organisms than larger plastic debris. (3 marks)\n\n(c) To conserve the Chinese White Dolphins, the government established a Marine Park (a marine protected area).\n(i) Discuss how the establishment of a marine park can promote the recovery of the dolphin population. (4 marks)\n(ii) State two active management measures (other than law enforcement against illegal fishing) that can be implemented in the Marine Park to enhance biodiversity. (2 marks)