Biology Paper 2 Questions and Answers - Sukellemo Joint Mock 2020/2021

SUKELLEMO JOINT MOCK
Kenya Certificate of Secondary Education
BIOLOGY PAPER 2
(Theory)
2  HOURS

Instructions to Candidates

• Answer all the questions in the spaces provided.
• 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. 40 MARKS
Answer all the Questions in this section.

1. The diagram below illustrates an experimental set up to compare relative amounts of a gas in inhaled air and exhaled air.
   
   
   1. On the diagram, show with arrows the direction of movement of inhaled and exhaled air into and out of the mouth. (2mks).
   2. What is the name of the gas being investigated in the experiment (1mk)
   3. What will happen to the lime water in. (2mks)
      Boiling tube A?
      Boiling tube B?
   4. Explain the observations made in (c) above. (3mks).
2. A human gene which is Y-linked controls premature baldness. One allele leads to normal hair pattern while the other produces premature baldness
   1. What are alleles? (1mark)
   2. If a man with premature baldness marries, work-out the phenotypes of his children. (Use letter R to represent gene for premature baldness). (4 marks)
   3. Explain why this trait is not observed in females (2marks)
   4. Give one other trait in man that is Y—linked (1mark)
3.  
   1. What is active transport? (1mk)
   2. State three factors that increase the rate of active transport. (3mks) 
   3. Give two roles of osmosis in animals. (2mk)
   4. What would happen if a plant cell is placed in a hypotonic solution (2mks)
4. The diagram below shows two fused bones of a mammal.
   
   
   1. Identify the fused bones. (1mk)
   2. Name:
      1. The bone that articulates at the point labelled A. (1mk)
      2. The structure labelled B. (1mk)
   3. State the type of joint formed at structure B. (1mk)
   4.    
      1. Name: the structure labelled C (1mk)
      2. State two functions of the structure named in d(i) above (2 mks)
   5.    
      1. Name the structure labelled D (1mk)
      2. State what happens to the structure during childbirth. (1mk)
5. Use the diagram below to answer the questions that follow;
   
   1. Name the class the plant belongs to. ( 1mk)
   2. Give three OBSERVABLE characteristics that place the plant to the class named in (a)above ( 3mks)
   3. If a cross section was done on the young stem, draw and label the section observed. (3mks)

SECTION B (40 MARKS)
Answer question 6 (compulsory) and either 7 or 8

6. In an ecological study, a grasshopper population and that of crows was estimated in a certain grassland area over a period of one year. the results are as shown in the table below.
   

   Months	J	F	M	A	M	J	J	A	S	O	N	D
   Number of adult Grasshoppers x 102	90	20	11	25	2500	1652	120	15	10	35	192	456
   NUmber of crows	4	2	0	1	8	22	7	2	1	1	5	15
   Amount of rainfall	20	0	55	350	520	350	12	10	25	190	256	350

   
   
   1.    
      1. What is the relationship between the rainfall and grasshopper population?(1 mark)
      2. Account for the relationship stated in a (i) above. (3 marks)
   2. Explain the relationship between the grasshopper population and that of the crows. (3 marks)
   3. If the data was used in the construction of pyramid of numbers, what would be the trophic of;(3 marks)
      1. Grasshoppers
      2. Crows
      3. The grass in the study area
   4. If the area studied was one square kilometer, state:
      1. one method that could have been used to estimate the crow population. (1 mark)
      2. One method that could have been used to estimate the grasshopper population.(1mark)
   5. Suggest what would happen f a predator for grasshoppers entered the study area. (2 marks)
   6. What is meant by the term carrying capacity? (1 mark)
   7. Why would the carrying capacity of wild animals in a woodland grassland be higher than that of cattle? (2 marks) 
   8. What is an ecosystem? (3 marks)
7. Describe how water from the soil reaches the leaves of a tall tree and eventually to the atmosphere.(20mks)
8. Explain how the human alimentary canal is adapted to perform its functions. (20mks).

MARKING SCHEME

SECTION A. 40 MARKS
Answer all the Questions in this section.

1. The diagram below illustrates an experimental set up to compare relative amounts of a gas in inhaled air and exhaled air.
   
   
   1. On the diagram, show with arrows the direction of movement of inhaled and exhaled air into and out of the mouth. (2mks).
      
   2. What is the name of the gas being investigated in the experiment (1mk)
      • carbon (IV)oxide;
        
        
   3. What will happen to the lime water in. (2mks)
      Boiling tube A? - Boiling tube A  Lime water remains clear
      Boiling tube B? - Boiling tube B A white precipitate is formed.
      
      
   4. Explain the observations made in (c) above. (3mks).
      • In tube A the level of Carbon (IV) Oxide in inhaled air is low; compared to high amount of Carbon (IV) Oxide exhaled from the body; due to high rate of respiring cells;
        
        
2. A human gene which is Y-linked controls premature baldness. One allele leads to normal hair pattern while the other produces premature baldness
   1. What are alleles? (1mark)
      • A pair of genes occurring on chromosomes, controlling a particular trait./ Alternative form of a gene controlling a particular trait
        
        
   2. If a man with premature baldness marries, work-out the phenotypes of his children. (Use letter R to represent gene for premature baldness). (4 marks)
      
   3. A pair of genes occurring on chromosomes, controlling a particular trait./ Alternative form of a gene controlling a particular trait.
      • The gene is located only on the y chromosome; /have no alleles on the chromosome; females do   not inherit y-chromosome/females have xx only;
        
        
   4. Explain why this trait is not observed in females (2marks)
      • Hairs on the pinna/ nose;
        
        
   5. Give one other trait in man that is Y—linked (1mark)
3.  
   1. What is active transport? (1mk)
      • Process that moves substances/ions/amino acids/sugar across the cell membrane against a concentration gradient by use of energy; OWTTE.
        
        
   2. State three factors that increase the rate of active transport. (3mks) 
      • Increase in oxygen concentration;
      • Increase in glucose concentration;
      • Increase in temperature towards optimum for best working of respiratory enzymes/optimum temperature for respiratory enzymes;
      • Optimum pH for best working of respiratory enzymes;
        
        
   3. Give two roles of osmosis in animals. (2mk)
      • Re-absorption of water from the kidney (tubules);
      • Absorption of water in the large intestines;
      • movement of water into the cells from tissue fluids;
        MARK THE FIRST TWO
        
        
   4. What would happen if a plant cell is placed in a hypotonic solution (2mks)
      • It gains water by osmosis; and become turgid ;
        
        
4. The diagram below shows two fused bones of a mammal.
   
   
   1. Identify the fused bones. (1mk)
      • Pelvic girdle/Pubic bones/ innominate bones;
        
        
   2. Name:
      1. The bone that articulates at the point labelled A. (1mk)
         • Sacral vertebra/Sacrum;
           
           
      2. The structure labelled B. (1mk)
         • Acetabulum;
           
           
   3. State the type of joint formed at structure B. (1mk)
      • Ball and socket joint;
   4.    
      1. Name: the structure labelled C (1mk)
         • Obturator foramen
           
           
      2. State two functions of the structure named in d(i) above (2 mks)
         • Its an aperture through which blood vessels nerves and muscles pass;
         • Reduce the weight of the pelvic girdle;
           
           
   5.    
      1. Name the structure labelled D (1mk)
         • Pubis symphysis;
           
           
      2. State what happens to the structure during childbirth. (1mk)
         • It relaxes thus expanding the size of pelvic cavity;
           
           
5. Use the diagram below to answer the questions that follow;
   
   1. Name the class the plant belongs to. ( 1mk)
      • Dicotyledonae;
        
        
   2. Give three OBSERVABLE characteristics that place the plant to the class named in (a)above ( 3mks)
      • They have broad leaves;
      • They have network veins;
      • Their floral parts are arranged in fours or fives or their multiples;
        
        
   3. If a cross section was done on the young stem, draw and label the section observed. (3mks)
      

SECTION B (40 MARKS)
Answer question 6 (compulsory) and either 7 or 8

6. In an ecological study, a grasshopper population and that of crows was estimated in a certain grassland area over a period of one year. the results are as shown in the table below.
   

   Months	J	F	M	A	M	J	J	A	S	O	N	D
   Number of adult Grasshoppers x 102	90	20	11	25	2500	1652	120	15	10	35	192	456
   NUmber of crows	4	2	0	1	8	22	7	2	1	1	5	15
   Amount of rainfall	20	0	55	350	520	350	12	10	25	190	256	350

   
   
   1.    
      1. What is the relationship between the rainfall and grasshopper population?(1 mark)
         • High rainfall is followed a month later by high grasshopper population/low rainfall is followed a month later by low population of grasshoppers;
           
           
      2. Account for the relationship stated in a (i) above. (3 marks)
         • vegetation/grass sprouts; vegetation/grass provide food for grasshoppers hence multiply rapidly; vegetation also offer shelter/camouflage for grasshoppers hence predators do not spot them easily;
           
           
   2. Explain the relationship between the grasshopper population and that of the crows. (3 marks)
      • Presence of large number of grasshopper is associated with large number of crows in the same month; Acc — the reverse. The crows feeding on grasshopper/predating on the grasshopper; if grasshopper population is low the crow population decrease due to migration to other areas in search of alternative food (sources);
        
        
   3. If the data was used in the construction of pyramid of numbers, what would be the trophic of;(3 marks)
      1. Grasshoppers - 2nd  (trophic) level/ primary consumers;
      2. Crows - 3rd  (trophic) level/secondary consumers;
      3. The grass in the study area -  1st (trophic) level/producers;
         
         
   4. If the area studied was one square kilometer, state:
      1. one method that could have been used to estimate the crow population. (1 mark)
         • Total count;
           
           
      2. One method that could have been used to estimate the grasshopper population.(1mark)
         • Capture re-capture;
           
           
   5. Suggest what would happen if a predator for grasshoppers entered the study area. (2 marks)
      • Vegetation/grass would sprout/increase due to decrease of grasshoppers; The predator would compete for food/grasshoppers with the crows (causing  some grasshoppers to migrate) rapidly declining grasshopper population;
        
        
   6. What is meant by the term carrying capacity? (1 mark)
      • Maximum number of organism an area/habitat can comfortably support without depletion of the available resources; OWTTE.
        
        
   7. Why would the carrying capacity of wild animals in a woodland grassland be higher than that of cattle? (2 marks) 
      • Cattle feed on the same type of food/grass (hence high competition food); while wild animals feed on a variety of foods/some are browsers while some are carnivores/; or  cattle occupy same ecological nitch; while wild animals occupy different ecological  nitches;
        
        
   8. What is an ecosystem? (3 marks)
      • A natural unit composed of abiotic and biotic factors; whose interactions; lead to self- sustain ing system;
        
        
7. Describe how water from the soil reaches the leaves of a tall tree and eventually to the atmosphere.(20mks)
   • Root hairs absorb water: by osmosis: from the spaces between the soil particles : passes into the root hair vacuole: through the cellulose cell wall and plasma/cell membrane: then through cell to cell in the cortex: or through intercellular spaces: then through the endodermis directing water into the xylem: water moves up in the xylem: in the vascular tissue. Once in the root xylem vessels water movement is aided by forces of capillarity: cohesion:adhesion:root pressure: and transpiration pull: into the stem xylem: water then enters into the xylem of the leaf veins/ leaf xyle: once in the leaves water moves into the mesophyll cells by osmosis: each time diluting the concentration of cell sap in the cells: this continues until water reaches the air spaces of the mesophyll cells: eventually escapes through stomata: as water vapor.
8. Explain how the human alimentary canal is adapted to perform its functions. (20mks).
   • The mouth has different types of teeth; that chew food increasing surface area for enzyme action;.
   • The mouth has salivary glands; that secrete saliva which lubricates and softens food; Salivary amylase breaks down starch into maltose;
   • The tongue rolls food into boluses; and pushes them to the back of the mouth for swallowing.
   • The esophagus is hollow for easy swallowing of food; it has muscles that contract and relax; to move food boluses through peristalsis
   • The alimentary canal is long; to provide a large surface area for digestion and absorption of food;
   • Small intestine is highly coiled; offering a large surface area for digestion and absorption of food;
   • the inner lining of the ileum has villi and micro-villi which increase surface area for absorption
   • Doudenum has openings of duct; through which pancreatic juice and bile get into the lumen;
   • The alimentary canal has goblet cells that secrets mucus; for lubrication of food; and protection of the wall from digestive enzymes;
   • The Brunner’s glands also secretes an alkaline fluid ;which provide an optimum pH for action of intestinal enzymes;Small intestines has intestinal glands; that secrete digestive enzymes;
   • the ileum has a rich network of blood capillaries that supply oxygen and remove metabolic waste from the intestinal tissues; and transports digested food and other nutrients
   • The walls have circular and longitudinal muscles; whose peristaltic contractions causes movement of food in the gut; and mixing of food with digestive enzymes;
   • The ileum has a thin epithelium; that allows soluble food materials to pass through rapidly into the bloodstream
   • The villi has lacteal; to transport absorbed lipids
   • The colon has a wide lumen; to increase surface area for absorption of water and mineral salts
   • The anus has anal sphincter muscles; that relax and contract to eliminate the indigestible and undigestible materials; max 20mks