Biology Paper 2 Questions and Answers - Achievers Joint Mock Exams 2023

INSTRUCTIONS

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

QUESTIONS

1. In tomatoes hairy stem are produced;
   1. By a dominant gen ‘H’ and hairless (smooth) stem by its recessive allele ‘h’. Using a punnet square, work out the outcome between two heterozygous hairy stemmed plants. (4mks)
   2. State the phenotypic ratio of the products (lmk)
   3. What will be the genotypes if the smooth variety is crossed with one of its parents? (lmk)
   4. State two ways in which. Genetics can be used in the field of Agriculture. (2mks)
2. The diagram below represents a blood dotting formed in the body of a mammal
   
   
   1. Name the cell labelled S and T. (2mks)
      S
      T
   2. State the function of the cell labelled S in the body of a mammal. (lmk)
   3. Describe how fibrin are formed. (3mks)
   4. Give two adaptations of cell labelled T to its functions. (2mks)
3. The diagram below represents a scheme diagram of movement of water from soil through leaves of a flowering plant into the atmosphere.
   
   
   1. 1. Name parts labelled Q R and S. (3mks)
      2. How is structure labelled R adapted to its functions. (2mks)
   2. On the diagram draw alternative site for water loss through the leaf. (lmk)
   3. Identify process (iii). (lmk)
   4. How is structure T adapted to its function? (lmk)
4. The diagram below shows some of the processes that take place in female reproductive system.
   
   
   1. Name process labelled
      I (lmk)
   2. Name the structure labelled T and R. (2mks)
      T
      R
   3. Identify hormones responsible for the formation of structuresT and R. (2mks)
   4. Explain what leads to processes at II. (3mks)
5. The diagram below shows three different types of neurones a long a reflex arc
   
   
   1. Identify the neuron labelled 1, 2 and 3 (3mks)
      1
      2
      3
   2. Using arrows show the direction of impulse transmission on the diagram. (lmk)
   3. Name the part of the spinal cord where the cell bodies of neurone 2 and 3 are located (lmk)
   4. Describe the transmission impulse across the part labelled P. (3mks)
6. During germination and growth of a cereal, the dry weight of endosperm, the embryo and the total dry weight were determined at two day intervals. The results are shown in the table below.
   
   
   1. Using the same axes, draw graphs of dry weight of endosperm, embryo and the total dry weight against time. (7mks)
   2. What was the total dry weight on day 5 (lmk)
   3. Account for;
      1. Decrease in dry weight of endosperm from day 0 to 10. (2mks)
      2. Increase in dry weight of embryo from day 0-10. (2mks)
      3. Decrease in total weight from day 0 to 8. (lmk)
      4. Increase in total dry weight after day 8. (lmk)
   4. State two factors within the seed and two outside the seed that cause dormancy.
      1. Within seed. (2mks)
      2. Outside the seed. (2mks)
   5. Give two characteristics of meristematic cells. (2mks)
7. Discuss the various evidences which show that organic evolution has taken place. (20mks)
8.  
   1. State any three differences between monosaccharides and polysaccharides. (3mks)
   2. Explain the biological functions of lipids to living organisms. (8mks)
   3. Describe the laboratory test for proteins using biurets test. (2mks)
   4. Describe the role of the following in mammalian digestive system.
      1. Pepsin (2mks)
      2. Bile (2mks)
      3. Hydrochloric acid - (2mks)

MARKING SCHEME

1. 1. Parental genotype Hh
       
      Offspring genotype HH: Hh; hh
                                         1: 2: 1
   2. 3 : 1
   3. Hh, Hh, hh, hh
   4. • plant and animal breeding ;
      • Genetically modified organisms (GMO’s);
2. 1. S – white blood cell /leucolyte;
      T – red blood cell / Erythrocyte
   2. Protection against infection/destroys pathogens; Rj- for defense alone unless it is qualified (1mk)
   3. Platelets / thrombocytes release thrombokinase / thromboplastin; (when exposed to air) which converts inactive prothrombin into active thrombin
      The enzyme thrombin converts the soluble fibrinogen into insoluble fibrin; (3mks)
   4. 1. Bioncave shape to provide a large surface area for diffusion of gases;
      2. Has haemoglobin that readily combines with oxygen/has high affinity for oxygen;
      3. Absence of nucleus to give more room/space for packing / accommodating more haemoglobin;
      4. Has enzyme carbonic anhydrase to speed up combination of carbon (IV) oxide with water; (mark 1st 2) = 2mks)
3. 1. 1. Q – piliferous layer; R – endosperm; S – pericycle; (3mks)
      2. Casparian strip, water proof, thus water can only pass via cytoplasm.
         • numerous starch granules acts as a source of energy; (3mks)
   2. See diagram (1mk)
   3. evaporation; (1mk)
   4. • Thickening to prevent collapsing;
      • Impregnated with lignin for support (any 1)
4. 1. I – ovulation; (1mk)
   2. T – graffian follicle; R – corpus luteum;
   3. T – follicle stimulating hormone
   4. R – lutenizing hormone; – (when sperm comes into contact with egg)
      (2mks)
      Acrosome bursts open and releases lytic enzymes; which dissolve egg membrane;
      Acrosome then turns inside –out froming a fine filament that penetrates the egg;
      Head of sperm enters ovum, tail is left outside the ovum;
      Vitelline membrane charges to fertilization membrane which stops any other sperm from entering ovum;
      Once in the cytoplasm, head bursts releasing male nucleus which then fuses with female nucleus to form a diploid zygote; (max 3)
5. 1. 1 – sensory neurone / Afferent neurone;
      2 – Relay neurone / intermediate neurone;
      3 – motor neurone/ Efferent neurone;
   2. The arrows point towards neurone 3 from 2 and 1:
   3. grey matter;
   4. Impulse reaching the dendrite end of relay/neurone 2 causes the synaptic vesicles to release acetylecholine/ transmitter/ transmitter chemical diffuses across the cleft; and causes the depolarization of the motor neurone; (any 3 x 1 = 3mks)
6. 1. Graph
   2. 41mg
   3. 1. food stored in endosperm was utilized by the growing / germinating plumule and radicle
      2. Food from the endosperm was taken to the embryo which was growing thus increased in weight.
      3. This is due to the energy lost through respiration i.e. not all the food the endosperm is utilized in the growth of the embryo.
      4. The ‘seedling has developed foliage leaves thus photosynthesis has started taking place.
   4. 1. • Immaturity of the embryo;
         • absence of enzymes / hormones;
         • presence of inhibitors ;
         • Impermeable seed coat; (any 2x1=2mks)
      2. Excess heat;
         • lack of water/oxygen
      3. • thin walls
         • dense cytoplasm
         • absence of vacuoles
7. Comaparative anatomy;
   Members of a phylum show similarities; the organisms have similar structure / organs performing similar function e.g presence of digestive , urinary and nervous systems;
   Vestigal organs/coccyx, appendix;
   Pentadactyl limbs in different animals e.g. monkey and rats, have bones arranged in a similar way/ these are examples of homologous structures / structure of similar origin but perform different function;
   Convergent / analogous structures like wings of birds and insects all these point towards common origin;
   Comparative embryology;
   Vertebrate embryos are (morphologically) similar; suggesting the organisms have a common origin/ Acc. When two embryos of mammals, reptiles and amphibians are compared they show similarities.
   Fossil records;
   These are remains of organisms preserved from naturally occurring materials for many years; they show morphological changes of organism over a long period of time; e.g. skull of man;
   Geographical distribution;
   Present continents are thought to have been a large land mass joined together; continental drift led to isolation that led to patterns of evolution; e.g. camels in S. America resemble those in Africa / tiger in Asia resemble jaguars in S. America;
   cell Biology;
   Occurrence of organelles / e.g. mitochondria, cytoplasm, nucleus; point towards a common origin (20mks)
8. 1. 
   2. functions of lipids
      • Storage purpose/energy reserve
      • oxidized to release energy
      • source of metabolic water
      • protection of delicate organs e.g. kidneys, eyeballs.
   3. Place a food substance in a test tube add a few drops of sodium hydroxide solution and shake well;
      • Add a few drops of 1% Copper (II) sulphate solution
      • shake well and observe the colour change;
      • If proteins are present purple coagulatios is formed;
   4. 1. Pepsin
         • Breaks down proteins into polypeptides;
      2. Bile
         • contains bile salts whose functions are – emulsification fats;
         • neutralize acid in chyme and provide alkaline medium
      3. hydrochloric acid
         • kills bacteria in the food
         • Activates the conversion of pepsinogen to active pepsin
         • Provides acidic medium for pepsin to function