Biology Paper 2 Questions and Answers - Samia Joint Mock Examination 2023

INSTRUCTIONS TO CANDIDATES

Answer all questions in Section A.
In section B answer question 6 (compulsory) and either question 7 or 8.

1. State two adaptations of the amphibian’s skin to gaseous exchange. (2mks)
2. Explain how the human nasal cavity is adapted to gaseous exchange. (3mks)
3. Explain why the amoeba does not acquire an elaborate gaseous system. (2mks)
4. Name the respiratory disease caused by Bordetella pertussis. (1mk)
A man experienced non-disjunction during meiosis. If the woman he married had normal gamete formation process.
1. Work out the likely phenotypes of their off springs. (4mks)
2. State two characteristics of individuals with Down’s syndrome. (2mks)
3. Give two advantages of transgenic plants. (2mks)
The diagram below is a side view of the human male reproductive system.
1. Name the parts labelled D and G. (2mks)
  D-
  G-
2. How are parts labelled E and H adapted for their functions? (4mks)
3. Give the names of two accessory sex glands and state their functions. (2mks)
  Accessory gland - ………………………………………………………………………………………………
  Function - ………………………………………………………………………………………………………….
  Accessory gland - ………………………………………………………………………………………………
  Function - ………………………………………………………………………………………………………….
The set up in the figure below was used to investigate a certain process in plants. Study it and answer the questions that follow.
1. Name the apparatus shown in the set up. (1mk)
2. Name the process that was being investigated. (1mk)
3. Explain what would happen to the air bubble in the capillary tube if the set up was placed in windy conditions. (2mks)
4. Other than wind, state four environmental factors that influence the process that was under investigation. (4mks)
The diagram below represents a bone found on the lower part of the body.
1. Identify the bone. (1mk)
2. Identify the parts labelled E and F. (2mks)
3. Name and give the functions of the parts labelled A and C. (4mks)
4. Name the material composing structure D. (1mk)
During germination and growth of cereal, dry weight of endosperm, embryo and total dry weight were determined at 2 days intervals and results recorded as shown below.
1. Using same axes, draw graphs of dry weight of endosperm, embryo and total dry weight against time. (7mks)
2. What was the total dry weight on the 5th day? (1mk)
3. Account for the:
  1. Decrease in dry weight of endosperm from day 0 to 10. (2mks)
  2. Increase in dry weight of embryo from day 0 to 10th day. (2mks)
  3. Decrease in total dry weight from day 0 to 8. (1mk)
  4. Increase in total dry weight after the 8th day. (1mk)
4. State two factors within the seed and two outside the seed that causes dormancy.
  1. Within the seed. (2mks)
  2. Outside the seed. (2mks)
5. What are the characteristics of meristematic cells? (2mks)
How is the mammalian ear adapted to its functions? (20mks)
Describe how free nitrogen in the air is made available to plants and carnivorous animals and finally circulated back into the atmosphere. (20mks)

MARKING SCHEME

1. State two adaptations of the amphibian’s skin to gaseous exchange. (2mks)
  - Moist to dissolve respiratory gas for faster gaseous exchange.
  - Thin lined with a one cell thick epithelium for faster diffusion of respiratory gases
  - Highly vascularized for faster / efficient transportation of respiratory gases.
2. Explain how the human nasal cavity is adapted to gaseous exchange. (3mks)
  - Lined with hair to trap dust particles/ foreign materials/ purify (the incoming) air.
  - Has mucus; to moisten/ warm the incoming air.
3. Explain why the amoeba does not acquire an elaborate gaseous system. (2mks)
  - Has a large surface area to volume ratio; for diffusion (across its cell membrane) is adequate.
4. Name the respiratory disease caused by Bordetella pertussis. (1mk)
  - Whooping cough
A man experienced non-disjunction during meiosis. If the woman he married had normal gamete formation process;
1. Work out the likely phenotypes of their offsprings. (4mks)
2. State two characteristics of individuals with down syndrome. (2mks)
  - Short body with stubby fingers
  - Cardiac malfunctions
  - Slit eye appearance
  - Reduced resistance to infection
  - Thick tongue
  - Mentally deficient. (mark first two)
3. Give two advantages of transgenic plants. (2mks)
  - Fast growth
  - (Increased) disease and pest resistance
  - Drought tolerance/ resistance
  - High/ increased yields
The diagram below is a side view of the human male reproductive system.
1. Name the parts labelled D and G. (2mks)
  - D - Urethra
  - G - Scrotum/ Scrotal sac
2. How are parts labelled E and H adapted for their functions. (4mks)
  - E – Has spongy like tissues that are filled with blood causing an erection.
  - H – Long and highly coiled to increase surface area for temporary storage of sperms.
3. Give the names of two accessory sex glands and state their functions. (2mks)
  - Accessory gland – Cowper’s gland
    Function – Secretes alkaline fluid that neutralizes the acidity along the urethra.
  - Accessory gland – Prostate gland
    Function – secretes alkaline fluid that to neutralize the vaginal fluids and activate the sperms.
  - Accessory gland – Seminal vesicle
    Function – Secretes alkaline fluid which contains nutrients for sperms.
The figure below shows a stem of a plant growing round a tree trunk. Study it and answer the questions that follow.
1. Name the apparatus shown in the set up. (1mk)
  - Potometer
2. Name the process that was being investigated. (1mk)
  - Transpiration
3. Explain what would happen to the air bubble in the capillary tube if the set up was placed in windy conditions. (2mks)
  - More water vapour would be blown away reducing saturation around the stomata increasing the rate of transpiration; leading to faster movement of the air bubble;
4. Other than wind, state four environmental factors that influence the process that was under investigation. (4mks)
  - Temperature
  - Humidity
  - Light
  - Atmospheric pressure
  - Availability of water
    (Mark first four)
    *(Rej; Wind/ Air)
The diagram below represents a bone found on the lower part of the body
1. Identify the bone. (1mk)
  - Pelvic girdle
2. Identify the parts labelled E and F. (2mks)
  - E – Ischium
  - F – Pubis
3. Name and give the functions of the parts labelled A and C. (2mks)
  - A – Acetabulum – It articulates with the ball of femur to form ball and socket joint.
  - C – Obturator foramen- it allows passage of blood vessels, nerves and muscles.
4. Name the material composing structure D. (1mk)
  - Flexible cartilage
During germination and growth of cereal, dry weight of endosperm, embryo and total dry weight were determined at 2 days intervals and results recorded as shown below.
1. Using same axes, draw graphs of dry weight of endosperm, embryo and total dry weight against time. (7mks)
  
  A=1mk
  S =1mk
  P =3mks
  C =1 ½ mks
  I = 1 ½ mks
2. What was the total dry weight on the 5th day? (1mk)
  - 38; +/−0.5
3. Account for the:
  1. Decrease in dry weight of endosperm from day 0 to 10. (2mks)
    - Stored food is hydrolysed into glucose and translocated to the embryo for respiration to produce energy required for germination.
  2. Increase in dry weight of embryo from day 0 to 10th day. (2mks)
    - New cells are made leading to growth of the embryo.
  3. Decrease in total dry weight from day 0 to 8. (1mk)
    - Rate of respiration is higher than that of synthesis of new materials for growth.
  4. Increase in total dry weight after the 8th day. (1mk)
    - First foliage leaves start photosynthesizing thus food accumulates in the seedling or is used in the formation of the structures of the new seedling.
4. State one factor within the seed and two outside the seed that causes dormancy.
  1. Within the seed. (1mk)
    - Presence of abscisic acid
    - Presence of germination inhibitors (mark first 1)
  2. Outside the seed. (2mks)
    - Lack of water
    - Unfavorable temperature
    - Absence of light in some plant varieties.
5. What are the characteristics of meristematic cells? (2mks)
  - They have a thin cell wall
  - They have a dense cytoplasm
  - They have no vacuole
How is the mammalian ear adapted to its functions. (20mks)
- Pinna; is wide/funnel-shaped to collect/gather sound waves; and direct them to the auditory canal into the ear;
- Eardrum/tympanic membrane is thin and light; to convert sound waves into vibrations;
- Ear ossicles/maleus, incus and stapes are of high density; to magnify/amplify sound waves;
- Oval window is smaller than eardrum; to magnify the sound waves; and direct them to the inner ear;
- Cochlea is long and coiled; to increase surface area; for attachment of receptor cells/sensory hairs; cochlea has many sensory hairs; which receive sound vibrations and generate impulses;
- Liquid or fluid/endolymph in cochlea; transmit sound vibrations; auditory nerve; transmit impulses to the brain for interpretation; Eustachian tube; link the mouth and middle ear to equalise pressure; between middle and outer ear to prevent damage to delicate eardrum;
- Round window; lose excess vibrations; to avoid continuous stimulation;
- Semi-circular canals; contain receptors for body balance and posture; External auditory canal cells produce/secrete wax; to trap dust particles/solid/micro-organisms that can damage eardrum; Max. 20 mks
Describe how free nitrogen in the air is made available to plants and carnivorous animals and finally circulated back into the atmosphere. (20mks)
- This is the cycling of nitrogen and its compounds in nature; plants absorb nitrogen in form of nitrates and then assimilate it into plant proteins; animals obtain this nitrogen in plant proteins through feeding on plants; when the animals die and decompose, they release the nitrogen in form of ammonia to the soil; free atmospheric nitrogen is converted into nitrates through a process known as nitrogen fixation; the process occurs in two ways: biological and non-biological; biological fixation of nitrogen is done by nitrogen-fixing bacteria; which are either free-living or symbiotic; symbiotic bacteria are of the genus Rhizobium; and are found in root nodules of legumes (such as pea, clover and alfalfa); the bacteria convert atmospheric nitrogen into ammonia; that is used directly by the leguminous plants to form nitrogen containing organic compounds (amino acids, nucleic acids, proteins); when plants die, the nodules release ammonium compounds into the soil; which are then converted to nitrites; by nitrifying bacteria of genus Nitrosomonas and Nitrococcus (nitrite bacteria) and then to nitrates by Nitrobacter (nitrate) bacteria; free-living micro-organisms that fix nitrogen include putrefying/saprophytic bacteria; (such as Azobacterspp, Clostridium and some algae such as Anabaena, Chlorella and Nostoc); the organisms fix nitrogen into ammonia by break down of protein material in dead organisms; the ammonia is converted to nitrites; then to nitrates; However, denitrifying bacteria (e.g. Pseudomonas denitrificans and Thiobacillus denitrificans); break down/reduce nitrates to nitrites, ammonium compounds and even gaseous nitrogen; a process known as denitrification; the process helps to release free nitrogen into the air for recycling; non-biological nitrogen fixing is carried out by lightning during thunderstorms; the lightning energy, causes atmospheric nitrogen and oxygen to combine forming oxides of nitrogen; which dissolve in rain water to form nitrous acid/nitric acid; that is washed down into the soil; the nitric acid formed reacts with other chemical compounds dissolved in soil water; to form nitrates; the nitrates are then utilized by plants; Max. 20 mks