BIOLOGY PAPER 2 - 2019 KCSE TAP TRIAL MOCK EXAMS (QUESTIONS AND ANSWERS)

QUESTIONS

1. The diagram below shows some components of a light microscope.
   
   
   1. Name the parts labeled            1mks
      K –
      M –
   2. State the functions of         2mks
      P –
      Q –
   3. A student was viewing a prepared slide of a plant cell under high power microscope. The features of the cell were blurred. Which one of the labeled parts of the microscope would the student use to obtain;-
      1. A sharper outline of the features            1mk
      2. Give the formula used to calculate magnification in a light microscope         1mk
   4. A student was preparing a section of a plant cell to be viewed on a light microscope. Give a reason for each of the following steps.                                            
      1. Cutting a very thin section          1mk
      2. staining the section                 1mk
      3. Putting the section in water.         1mk

2. Haemophilia is a sex linked disorder due to a recessive gene. A carrier woman married a normal man. Let H represent gene for normal condition and h to represent gene for haemophilic condition.
   1. State the genotypes of
      1. Man           1mk
      2. woman         1mk
   2.  
      1. Using a punnet square, show the genotypes of the children resulting from this marriage  3mks
      2. State the probability of getting a carrier daughter.                                                  1mk
   3. Give an explanation why haemophilia is more common in males than in females.   2mks

3. In an experiment a group of students set up the test tubes as shown below
   
   
   1. What was the aim experiment?                                                                         1mk
   2. Why was pyrogallic acid included in the gas jar. A?                                             1mk
   3. What results would you expect in each of the gas jar A and B at the end of experiment?        2mks
   4. State two artificial ways of breaking seed dormancy.                                                          2mks
   5. Name two harmones that bring about rapid cell division in plants                         2mks

4.  
   1.  
      1. Distinguish between single circulatory system and closed circulatory system.   2mks
      2. Name the blood vessels that transports blood from
         1. small intestines to the liver     1mk
         2. Lungs to the heart             1mk
   2.  
      1. Name one defect of circulatory system in humans.       1mk
      2. State three functions of blood other than transport.        3mks      

5. An experiment was set up to demonstrate the necessity of carbon (IV) oxide for photosynthesis in a certain green plant as shown below. The plant was first kept darkness for 48 hours before the experiment.    
   
   
   1. Why was the plant kept in darkness for 48 hours before the start of this experiment.         1mk
   2. What was the role of sodium hydroxide?     1mk
   3.  
      1. What happened to the leaf in the flask when it was tested for presence of starch after the set up was exposed to light for a day?.  1mk
      2. Give reasons for your answer in (c) I above   2mks    
   4. Suggest a control for this experiment.   1mk
   5. Name other two limiting factors in this experiment.        2mks      

SECTION B         40MKS
Answer question 6 (Compulsory) and either question 7 or 8 in the spaces provided after question 8.

6. A certain experiment was performed to demonstrate the effect of sweating on human body temperature. Boiling tubes A and B were filled each with water their initial temperatures recorded. This was repeated after every 5 minutes. The surface of tube A was continuously wiped with a piece of cotton wool which had been soaked in methylated spirit. The results are as shown below
   

   Time (min)	Temperature 0c in tube
   	A	B
   0	80	80
   5	54	67
   10	40	59
   15	29	52
   20	21	47
   25	18	46

   
   
   1. On the same axis, plot graphs of water temperature against time (min)         8mks                                              
   2. Find the rate of cooling in A   1mk
   3. Why was test B included in the set up?       1mk
   4. Name two ways through which heat is lost in tube B.       2mks
   5. State the expected results if tube A was insulated.    1mks
   6. Name the structures in the following organisms that would insulate heat loss.
      1. Birds        1mk
      2. Mammals             1mk
   7. Name any two receptor cells on the skin of man.        2mks
   8. Describe the response of hair on the skin during cold weather.     3mks

7.  
   1. Describe gaseous exchange in alveolus.        8mks
   2. Describe the process of exhalation in mammals.  8mks
   3. Discuss the characteristics of gaseous exchange sites in an animal.   4mks
8. Discuss the nitrogen cycle.     20mks

MARKING SCHEME

1.  
   1. K-eye piece
      M -coarse adjustment knob
   2. P- concentrates the light
      Q-Brings the image into focus and magnifies it
   3.  
      1. N
      2. Eye piece magnification × objective lens magnification
   4.  
      1. for light to pass through easily
      2. To make the features more clearly and distinguishable.
      3. For cells to remain turgid

2.  
   1.  
      1. X^HY
      2.  X^HX^h                       
   2.  
      1. Parental phenotypes         Female carrier                                    Normal Male
         
      2. Probability: ½ (50%)
   3. Males have only one X chromosome which if it carries the single recessive allele, it will express itself fully; females can only express the gene in homozygous state; thus reducing their chances.
3.  
   1. To show that oxygen is necessary for germination
   2. To absorb oxygen present in air.
   3. A- No germination
      B- Germination occurred
   4. Scarification, soaking in gibberellic acid, boiling seeds, appropriate temperatures (mark the first two)
   5. Gibbberellins; auxins;
4.  
   1.  
      1. Single circulation is where the blood passes through the heart once to make a complete circulation while closed the blood passes through the heart twice to make a complete circulation.
      2. Hepatic portal vein
   2. pulmonary vein
      1. Thrombosis; varicose vein; arteriolosclerosis; hypertension ( mark the first one)
      2. -Regulation of the body temperature;
         -Regulation of the PH of body fliud;
         -Defense against diseases- disease causing microorganisms;
   3. Prevent excessive bleeding by enhancing clotting; ( mark first three)
5.  
   1. To destarch the leaf
   2. To absorb carbon(IV) oxide
   3.  
      1. Starch absent
      2. It lacked carbon(IV) oxide; therefore photosynthesis could not take place;
   4. A leaf is enclosed in a flask but instead of sodium hydroxide, water is used or leaf that was enclosed in the flask is tested for starch.
   5.  
      1. Light intensity
      2. Chlorophyll
      3. Temperature

6.  
   1. As shown on the graph
   2. ^(80-18) /₂₅ = ⁶²/₂₅ = 2.48^oC
   3. Control experiment.
   4. –Convention
      - Radiation
   5. Less heat loss
   6.  
      1. Feather
      2. Fur and hair; (tied)
   7. -Skin thermoreceptors
      -Hypothalamus
   8. Erector pili muscle contract; hair stands upright trapping air; air being a bad conductor of heat prevents heat loss;
7.  
   1. Lungs have numerous alveoli to increase S.A for diffusion of gases; alveoli have thin membrane which minimizes resistance against gases; blood flowing in the capillaries contains less oxygen and more C0₂ since it is from the body tissue; alveoli are supplied with air through bronchioles which link them to the trachea; alveoli are supplied with many capillaries containing blood to transport gases; air in the alveoli contain more oxygen and combine with haemoglobin, forming oxyhaemoglobin; C0₂ diffuses out of the blood into the alveoli ;from where it is exhaled; (8mrks)
   2. Internal intercostal muscles contracts and external intercostal muscles relax; The ribcage moves downwards and inwards; diaphragm muscles relax; diaphragm assumes its dome-shaped; volume in the thoracic cavity decreases; resulting in increase in lung volume, pressure in the lung increases; air is then forced out of the lungs;  (8marks)
   3. Thin membrane and epithelial lining for easy diffusion of respiratory gases;
      Highly folded surfaces to provide large surface area for efficient diffusion of gases;
      Moist surfaces for dissolving the gases before they diffuse;
      Highly vascularized surface for efficient transport of gases to maintain high concentration gradient (4 marks)

8. Nitrogen fixation; is the process of converting Nitrogen to Nitrates; and is done through three means. During thunderstorm/ lightning energy combines, atmospheric Nitrogen gas with oxygen to form oxides of nitrogen; which dissolve in water to form nitric acid and nitrous acid; acid combines with chemical compounds to form nitrates which are absorbed by plants; Symbiotic bacteria such as Rhizobium; which are found in root nodules of leguminous plants; fix free nitrogen to nitrates; Free living bacteria e.g clostridium, Azotobacter, fix nitrogen; and also non-bacteria fixers e.g Nostac algae / chlorella/ anabaena, fix nitrogen to ammonia; Nitrification; is the process of oxidizing ammonium compounds or nitrites to nitrates; Ammonia is oxidized into nitrites by nitrifying bacteria e.g nitrosomonas and nitrococcus; Nitrites are converted into nitrates b nitrifying bacteria e.g nitrobacter; Absorption and assimilation; Nitrates is then absorbed by the plants; plants use nitrates to form plant proteins; animals feed on plants and convert plant protein into animal protein; Death and decomposition; plants and animals die and are decomposed by saprophytic bacteria and fungi; Decomposition release ammonia which is converted to nitrites the to nitrates; Denitrification; Process in which nitrates are reduced into nitrites or atmospheric Nitrogen; This is done by denitrifying bacteria such as pseudomonas denitrificans and Thiobacillus denitrificans; they utilize oxygen released to carry out respiration.