Biology Paper 2 Questions and Answers - Samia Joint Mock Examination 2021/2022

Instructions to Candidates

Answer all questions in section A by filling in the spaces provided.
In Section B, Answer Question 6 (Compulsory Question) and any other one question from the remaining two questions (i.e. 7 & 8)

SECTION A. (40 MARKS)
Answer all questions in this section in the spaces provided.

The set up below show an experiment in which iodine solution and starch were separated by a semi permeable membrane.
1. Name the process that is being investigated. (1mk)
2. 1. State the observations made in the two arms of the U-tube. (2mks)
    Arm A …………………
    Arm B………………....
  2. Account for your answer in (i) above. (2mks)
3. 1. State two applications of the process in (a) above in animals. (2mks)
  2. Name one factor that will affect the process named in (a) above. (1mk)
1. 1. Name the components of blood that are absent in the glomerula filtrate. (2mks)
  2. Give a reason for your answer above. (1mk)
2. 1. What would happen if a person produced less antidiuretic hormone. (1mk)
  2. Name the disease described in b (i) above? (1mk)
3. Explain what happens to excess amino acids in the liver of humans. (3mks)
1. 1. Premature baldness in a sex linked trait. A bald headed man marries a woman. Work out the genotype of the off springs. Use letter B to represent the gene for bald head. (4mks)
  2. What is the probability that their daughter will have premature baldness? (1mk)
  3. Give a reason for the answer in 3 (ii) above. (1mk)
2. The diagram below show the template strand of a Deoxyribonucleic acid molecule.
  
  A G T A T C G
  1. Draw a diagram to represent a complimentary RNA strand. (1mk)
  2. State one advantage of polyploidy in plants. (1mk)

The table below shows some of the components found in 100cm3 of cow’s milk, breast milk and breast milk substitute (formula milk).

component	cow’s milk	Breast milk	breast milk substitute
Protein/g	3.3	1.2	1.3
Sugar/g	4.2	6.4	7.0
Fat/g	3.0	4.0	1.4
Calcium /mg	120.0	120.0	49.0
Iron/mg	0.1	0.1	0.5
vitamin C/mg	1.0	2.0	8.3
Vitamin D/μg	20.0	200.0	1.2

Name two main components of a normal healthy diet that do not appear in the table.(2mks)
State which type of milk would be least likely to ensure the development of healthy bones and teeth, and explain your answer? (2mks)
Type of milk …………………
Explanation……………………
State which type of milk would provide a baby with the greatest amount of energy? Give your reasons (2mks)
Type of milk ………………
Reasons…………………
Suggest why babies fed on breast milk may have more resistance to diseases than those fed on any other type of milk. (2mks)

1. What is the difference between Darwinian and Lamackian theories of evolution? (2mks)
2. What is meant by the following terms? Give an example in each case.
  1. Homologous (1mk)
    Example (1mk)
  2. Analogous (1mk)
    Example (1mk)
  3. Vestigial Structures (1mk)
    Example (1mk)

SECTION B
Answer question 6 (Compulsory) in the spaces provided and either question 7 or 8 in the spaces provided.

The menstrual cycle is a sequence of events repeated monthly in the female reproductive system. The table below shows the concentration of oestrogen and progesterone hormones and body temperatures of female against time.

Time in days	Oestrogen mg/100cm³	Progesterone mg/100cm³ of blood	Temperature in 0ºC
1	20	0	36.4
3	25	0	36.7
5	30	0	36.7
7	35	0	36.8
9	48	0	36.6
11	64	0	36.7
13	80	0	36.4
15	140	50	36.6
17	70	130	37.2
19	60	160	37.1
21	130	130	37.2
23	130	90	37.0
25	80	50	37.2
27	20	0	36.4

Using the same axes draw graphs of oestrogen and progesterone against time. (8mks)
State the possible event taking place in the uterus during the first week. (1mk)
State the events taking place in the ovary between day 1 and day 13. (2mks)
Account for the sudden increase in the progesterone concentration between day 14 and day 18. (2mks)
Account for the change in temperature between day 14 and 17. (1mk)
Account for the change of the curve of progesterone between day 19 and 27. (2mks)
State the function of the following:
1. Testes. (2mks)
2. Sertoli cells (1mk)

1. State four industrial applications of anaerobic respiration. (4mks)
2. Describe the mechanism of gaseous exchange in humans. (16mks)
1. Describe biological nitrogen fixation in leguminous plants. (5mks)
2. Explain how abiotic factors affect plants. (15mks)

MARKING SCHEME

1. Diffusion
2. 1. Brown color of iodine solution seen
    Arm B - Blue black colour seen
  2. Iodine particles/molecules move from arm A where they are in high concentration by diffussion; across pores on semi-permeable membrane into arm B. Iodine-starch reaction results to formation of blue-black color
3. 1. - Absorbtion of nutrients in alimetary canal
    - Reabsorbtion of weight substances in the nephron/kidney/ kidney tubules
    - Gaseous exchange in alveoli / lungs
  2. - Surface area to volume ratio
    - Thickness of the membrane
    - Concentration gradient
    - Size of moleculkes
    - Temperature; (mark 1st one)
1. 1. - Blood cells/(red blood cells & white blood cells and platelets)
    - Blood proteins/ globulin and fibrinogen
  2. Are too large to pass through
2. 1. Less water would be reabsorbed and alot of dilute urines is produced
  2. Diabetes inspidus
3. Excess amino acids are deaminated by removal of amino group; the amino group is converted to ammonia; which combines with carbon(iv) oxide to form urea; that is excreted by the kidney
1. 2. ^O/₂= 0% / Nil/ None
    Reject ^O/₄= 0
  3. The gene for baldhead premature baldness is on the Y-Chromosome, which girls do not inherit from their father
2. 1. U C A U A G C
  2. - Resistance to diseases/ pests/ adverse weather conditions
    - Increased yield
    - Early maturity
      (Mark the 1st point)
1. 1 - Folate/Vitamin B
  2 - Dietary fibre
  Accept water
2. Breast milk substitute;
  Explanation - Has least amount of calcium and vitamin D necessary for healthy bone and teeth formation
3. Breast milk substitute;
  Explanation - Has highest level/ amount of sugar which is the main respiratory sustrate
4. Contains antibodies;(and other elements) that protect baby from illness/ chronic diseases/ allows mother to pass immunity to her baby
1. Darwinian
  - Evolution occurs through adaptation by organisms to their environment. Environment can select against or for a particular organism (Natural Selection)
  Lamarkian
  -Development of body parts is directly proportional to their utilization and acquired characteristics are inheriter (use and disuse)
2. 1. Structures that have a common basic plan and a common basic plan and a common embryonic origin, but modified to perform different functions
    Examples - Beaks of birds/ mouth parts of insects/ pentadactyl limbs
  2. Structures that have different basic plan/embryonic origin but modified to perform similar functions
    Examples - Wings of insects and wings of birds
  3. Structures that have ceased to be functional over a long period of time hence reduced in size
    Example - Caecum/ Nicti membrane/ Appendix/ Coccyx bone/ Ear muscles/ Body hair in human being
2. Healing and repair of the endometrium
3. - Development of the graafian follicle
  - Production of oestrogen
  - Maturation of graafian follicle/ ovulation
4. Ovulation (just) occurred; need to prepare endometrium for implantation/ stimulate thickening of endometrium for implantation
5. Due to increase in progesterone/ activities leading to proliferation/ thickening of endometrium
6. Fertilization failed to take place, corpus luteum degenerates; hence no more production of progesterone
7. 1. (Site for) spermatogenesis/ sperm formation
  2. Nourishes spermatozoa/ sperm ceus
1. - Baking of bread
  - Brewing of beer/wine
  - Formation of dairy products e.g cheese/ yoghurt/ sour milk
  - Formation of organic acids e.g oxalic acid/ citric acid/ vinegar (ethanoic acid)
2. Inhalation
  External intercostal muscles contract while internal intercostal muscles relax
  - raising the rib cage upwards hence flatten
  - volume of thoracic cavity increases and pressure decreases(than atmospheric pressure)
  - the higher the air pressure in the atmosphere forces air into the lungs/the lungs inflate
  - Oxygen in the inhaled air dissolves in moisture in the alveolus and diffuses across alveolar wall through gradient
  - CO₂ in the blood diffuses across capillary and through alveolar wall into the lungs due to concentration gradients
    Exhalation
  - External intercostal muscles relax while intercostal muscles contract
  - Cusing rib cage to move downwards and inwards
  - muscles of the diaphragm relax and form a dome shape
  - making the volume of thoraic cavity to decrease while pressure increases
  - Higher pessure in the thoracic cavity forces air out of the lungs/ deflates the lungs
1. Legumes from symbiotic relationship with rhizobia/ nitrogen fixing bacteria resulting in symbiosis leading to formation of root nodules
  - within which rhizobia convert atmospheric nitrogen into ammonia that is used by plants
2. Wind
  in windy conditions the rate of transportation increases
  - an agent of pollination temperature; changes in temperature affects rate of photosynthesis and other biochemical reactions/ metabolic reactions/ enzymatic reactors
  - increase in tempreature increases rate of transportation
  - lower temperature/ temp below optimum inactivates enzymes hence lower rate of reactions
  - optimum temperature enzymes work best hence maximum enzymes activity
    Light
  - Avail energy/ correct light wavelength for photosynthesis
  - some plants need light for flowering/ photopendum
  - seeds like lettuce require humidity
  - when humidity is low rate of transpiration increases
    pH
  - Ech plant required a specific pH to grow well either acidic/ alkalinity/ neutral
  - Salinity
    Plants with salt tolerant tissues grow in the saline area
  - plants in estovaries are able to adjust to salt fluctuations
    Topography
  - North facing slopes lands home more plants than south facing slope
  - Plants on windward side home stunted distorted growth
    Water
  - is needed for germination
  - it is a raw material for photosynthesis
  - dissolves mineral salts
  - provides turgidity hence support in plant
    Atmospheric Pressure
  - At low atmospheric pressure there is increases rate of transpiration
  - affect amount of oxygen for respiration
    Mineral Salts/ trace elements
  - Plants thrive well where there are mineral salts in the soil
  - plants living in the soil deficient in particular mineral element have special methods of obtaining it
  - (e.g. leguminous plants by nitrogen fixation, insectivorous plants by feeding on insects)