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

INSTRUCTIONS TO CANDIDATES

• This paper consists of two sections. Section A and section B.
• Answer ALL questions in section A in the spaces provided. In section B answer question 6 (compulsory) and either question 7 or 8 in the spaces provided after question 8

                                                                                            SECTION A:
                                                                Answer all the questions in the spaces provided.

1. A biological washing powder contains an enzyme. The enzyme removes stain such as blood from clothes by digestion when the clothes are soaked in water with powder.
   1. What is an enzyme? (1 Mark)
   2. Identify two possible enzymes that are found in the washing powder above. (2 Marks)
   3. Would the stains be removed faster with the powder in water at 30oC or 150C. (1 Mark)
   4. Explain your answer in (c ) above (2 Marks)
   5. Why would boiling the clothes soaked with the washing powder do not remove the stains? (2 Marks)
2. The pedigree chart below illustrates the inheritance of haemophilia in a given a given family.
                                            
   1. Suggest the possible genotype of: (2 Marks)
      Individual 1 
      Individual 4
   2. Using a punnet square, work out the possible phenotypes of offspring’s, if individual 4 married a haemophiliac male. (4 Marks)
   3. Explain why there are no carrier males. (1 Mark)
   4. Name a condition in man that is due to chromosomal mutation. (1 Mark)
3.  
   1. Distinguish between pyramid of numbers and pyramid of biomass. (2 Marks)
   2. From an ecological study, students formed the following food web.
                        
      From the food web, construct two food chains with lizard as a tertiary consume. (2 Marks)
   3.  
      1. Which organism has the least biomass in the ecosystem. (1 Mark)
      2. Give reasons for your answer (3 Marks)
4. The diagram below shows how blood sugar in mammalian body is regulated.
                         
   1. Explain what happens during corrective mechanism P. (3 Marks)
   2. Name two organs involved in corrective mechanisms P and Q. (2 Marks)
   3. State the reasons why glucose level should be maintained constant. (2 Marks)
   4. What is osmoregulation? (1 Mark)
5. The diagram below shows the internal arrangement of muscles in the eye.
                                                    
   1. How is the pupil affected by contraction of ;
      1. Circular muscles (1 Mark)
      2. Radial muscles (1 Mark)\
   2. Where are light sensitive cells located in the eye? (1 Mark)
   3. What is short sightedness? (2 Marks)
   4. Explain why cones have a higher visual acuity as compared to rods. (2 Marks)
   5. State one defect that is heritable. (1 mark)
      
                                                                                  SECTION B:
                                                         Answer question 6 and either question 7 or 8.
6. The diagram below is obtained from measurements of growth in the leaf petiole of a certain plant. The relative growth rate is calculated and the data is obtained as shown below.
   

   Time in days	0	1	2	3	4	5	6	7	8	9
   Relative growth rate(cm/day)

   
   
   1. Plot a graph of relative growth rate against time. (5 Marks)
      
   2. State two functions of a leaf petiole. (2 Marks)
   3. State two characteristics of cells found in the region of cell division. (2 Marks)
   4. Account for the shape of the curve between the following days (3 Marks)
      1. 2 – 5.
      2. 6 – 8 (3 Marks)
      3. 8-9 (3 Marks)
   5. Distinguish between primary growth and secondary growth in a flowering plant. (2 Marks)
7. Explain how abiotic factors affect plants. (20 Marks)
   1. Describe how the following supports the theory of evolution. (4 Marks)
      1. Geographical distribution of organisms
      2. Comparative anatomy
   2. Describe how hormones regulate the menstrual cycle in human beings. (16 Marks)\

                                                                         MARKING SCHEME

1. A biological washing powder contains an enzyme. The enzyme removes stain such as blood from clothes by digestion when the clothes are soaked in water with the powder.
   1. What is an enzyme? (2mks)
      • An organic catalyst that is produced by a living cell and speeds up the rate of a chemical reaction without itself being changed or destroyed or consumed.
   2. Identify two possible enzymes that are found in the washing powder above. (2mks)
      • Proteases
      • Lipases
   3. Would the stains be removed faster with the powder in water at 30oC or 150C. (1mk)
      • At 30°C
   4. Explain your answer in (c ) above (2mks)
      • Enzyme activity is at its optimum and enzymes quickly digest the protein that forms some of the blood stains
   5. Why would boiling the clothes socked with the washing powder do not remove the stains? (2mks)
      • Boiling denatures enzymes making them ineffective at digesting the protein that cause the stains.
2. The pedigree chart below illustrates the inheritance of haemophilia in a given family.
   Suggest the possible genotype of: ( 2 Marks)
   Individual 1 X^hY
   Individual 4 X^HX^h
   1. Using a punnet square, work out the possible phenotypes of offspring’s, if individual 4 married a haemophiliac male. (4 Marks)
      X^hY   X   X^HX^h;
      

      	Xh	Y
      XH	XHXh	XHY
      Xh	XhXh	XhY

   2. Explain why there are no carrier males. (1Mark)
      • Males only have one X chromosome
   3. Name a condition in man that is due to chromosomal mutation. (1Mark)
      • Klinefelter’s syndrome
      • Turner’s syndrome
      • Down’s syndrome
3.  
   1. Distinguish between pyramid of numbers and pyramid of biomass. (2mks)
                                                  
   2. From an ecological study, students formed the following food web.
      • Pyramid of number is a pictorial representation of organisms number at each trophic level in an ecosystem while pyramid of biomass is a pictorial representation of dry weight of organism species at each trophic level of an ecosystem.
        From the food web, construct two food chains with lizard as a tertiary consumer. (2mks)
        
   3.  
      1. Which organism has the least biomass in the ecosystem. (1mks)
         • Hawk
      2. Give reasons for your answer (3mks)
         • Some energy is lost through indigestible food through feeding
         • Some energy is lost during respiration in form of heat
         • Some energy is lost through defecation.
4.  
   1.  
      • Excess glucose is converted to glycogen and stored in the liver/ muscle cells.
      • Excess glucose is oxidised to release energy
      • Some glucose is converted into fats and stored in adipose tissue.
   2. Pancreas and liver
   3. To avoid fluctuation in osmotic pressure which disrupt metabolism; Enough glucose is required for normal functioning of the cells.
   4. Maintenance of constant internal osmotic pressure.
      OR
      Maintenance of water and ion concentration in an organism at a constant state.
5. The diagram below shows the internal arrangement of muscles in the eye.
                                              
   1. How is the pupil affected by contraction of ;
      1. Circular muscles (1mk)
         • Pupil becomes smaller
      2. Radial muscles (1mk)
         • Pupil widens
   2. Where are light sensitive cells located in the eye. (1mk)
      • Fovea centralis
   3. What is short sightedness? (1mk)
      • A condition in which light rays from a distance object are brought to focus in front of the retina while those near are clearly focused.
   4. Explain why cones have a higher visual acuity as compared to rods. (2mks)
      • Cones lack retinal convergence (each one has its own bipolar neurons which links it to optical nerve) while rods show retinal convergence (several rods connected to one bipolar neurons)
   5. Nightblindness
6.  
   1.  
                                  
   2.  
      • Supports the leaf in position to trap light for photosynthesis;
      • Contains xylem tissue to transport water and dissolved mineral salts to the leaf for photosynthesis, and phloem to transport synthesized food to the rest parts of a plant;
   3.  
      • Dense cytoplasm;
      • Thin cell wall;
      • Numerous mitochondria;
      • Very small / No sap vacuole;
   4.  
      1. 2-5 There is a fast growth rate; because the leaf is very young; and cells are actively dividing and elongating;
      2. 6-8 There is reducing rate or relative growth; of the petiole. This is because the cells if the petiole/leaf are no longer dividing and elongating; instead the cells are becoming differentiated;
      3. 8-9 Growth ceases; /very little growth because all cells are differentiated; and has formed permanent tissues;
   5.  
      • Primary growth takes place at shoot tip and root tip leading to increase in length due to activity of apical meristems;
      • Secondary growth leads to increase in girth in stems due to activity of lateral meristems / vascular cambium;
7.  
   • Wind;
     Windy conditions transpiration;
     Wind disperses fruits/seeds/spores; an agent of pollination;
   • Temperature;
     Change in temperature affect rate of photosynthesis/other biochemical reactions/ metabolic/enzymatic reactions; rise in temperature rises transpiration.
   • Light;
     (Green) plants need light for photosynthesis;
     Some plants need it for flowering;
     Some seeds (like lattice) require it for germination;
   • Humidity
     When humidity is low, transpiration rate rises;
   • PH
     Each plant requires specific PH to grow well;
     Acidic or alkalinity or neutral
   • Salinity
     Plants with salt tolerant tissues (e.g. mangrove) grow in saline area; plants in estuaries adjust to salt fluctuations;
   • Topography
     North falling slopes in temperate lands have more plants than south facing slopes;
     Windward side plants have stunted and distorted growth; leeward side plants are stunted/wind ward normal growth;
   • Rainfall/water
     Few plants in dry areas/where rainfall is less;
     Water for germination;
     Water as a raw material for photosynthesis;
     Water as solvent for mineral salts;
     Provides turgidity;
     Water for dispersal;
   • A medium of transport of plant nutrients;
   • Mineral salts
     Plants thrive (grow well in soils with mineral salts)
     Plants living in soil with deficiency of particular element have special methods of obtaining it. Legumes obtain nitrogen by nitrogen fixation /carnivorous plants/insectivorous plants, carnivorous trees obtain their nutrients from mycorrhizal association;
8.  
   1.  
      1. Describe how the following supports the theory of evolution. (4mks)
         1. Geographical distribution of organisms
            • Based on the theory that before the continental drift, there was a single land mass; with continental drift members of the population of originally the same species become separated and isolated by geographical barriers such as seas/oceans.
            • They separated into different continents. The result of the isolation was evolution of different species, examples are members of the cat family in different continents such as the panthers and jaguars in S, American Amazon forest. (Leopards and Cheetahs in African Congo Forest, Tigers in Aston forests)
         2. Comparative anatomy
            • Based on the comparison of different structures; Homologous structures; are those having a common ancestral or embryological origin but perform different functions. E.gPentadectyl limb plan of vertebrates; (which has evolved in class mammalian into using for flying in bats, long fast running legs in horse and flipper from swimming is wholes) Divergent evolution;
            • Analogous structures have different ancestral/embryological origin but have evolved to perform similar functions (due to exploitation of similar ecological habitats) e,g wings of insects-convergent evolution.
   2. Describe how hormones regulate the menstrual cycle in human beings. (16mks)
      • Immediately after menstruation, the pituitary gland is stimulated to secrete follicle stimulating hormone (FSH) which stimulates the ovary leading to start of development of a new graffian follicles.
      • Higher concentration of follicle stimulating hormone stimulates the ovary tissues to secrete Oestrogen hormone.
      • Oestrogen hormone brings about healing and repair of the uterine wall and its higher concentration stimulates the pituitary gland to secrete luteinizing hormone (LH0
      • Luteinizing hormone brings about ovulation. This cause reorganization of remnants of graffian follicle to form corpus luteum. It also stimulates corpus luteum to secrete progesterone hormone.
      • Higher concentration of luteinizing hormone inhibits secretion of estrogen.
      • Progesterone hormone leads to proliferation of inner lining of the uterine wall in readiness for implantation.
      • When conception occurs the progesterone hormone maintains pregnancy up to birth and inhibits production of follicle stimulating hormone (FSH)
      • If no conception occurs, progesterone level falls drastically leading to degeneration of corpus luteum hence menstruation.