Biology Paper 3 Questions and Answers with Confidential - Form 3 End Term 1 Exams 2022

INSTRUCTIONS TO CANDIDATES
Answer ALL the questions in the spaces provided.

1. You are provided with
   Spécimen X
   Solution Y
   Solution Z
   
   1. Examine the outer and inner leaves then record your observations (4mks)
   2. Using a scalpel, cut and measure 6strips of 3cm length of the specimen X. Place 3 strips into a solution labeled Y, another 3 strips into a solution labeled Z. The experimental set up is allowed to stand for 20 minutes.
      
      1. What observations would be made after 20 minutes when the strips are touched (2mks)
         Strips in solution Y
         Strips in solution Z
      2. Account for the observations recorded in (b) (i) above (4mks)
2. You are provided with actual specimens of plant parts Q and K
   
   1.      
      1. Using external features only identify the part of the plants (2mks)
      2. Give three reasons for your answer in (a) (i) above (3mks)
   2. With reasons state the class to which the plants from which the specimens were obtained belong (4mks)
   3. State two observable features that adapt specimen Q for gaseous exchange (2mks) 
   4. Using the dichotomous key provided, indentify the identity of the specimens Q and K in each case show the sequence; the steps in the key that you followed to arrive at the identity. (4mks)

1.    
   1. Leaf parallel veined……………………………………………..go to 2
   2. Leaf net veined …………………………………………………go to 4
2.      
   1. Leaf purple in colour…………………………..………Tradescantia spp
   2. Leaf green in colour …………………………… ……………….go to 3
3.      
   1. Leaf with thorns on margin………………… ……………Kalanchoe spp
   2. Leaf smooth on the margin……………… ……………………Zea mays
4.      
   1. Leaf sample………………………… …………………………….go to 5
   2. Leaf compound……………………………………………………go to 8
5.      
   1. Leaf margin entire …………………………………………………go to 6
   2. Leaf margin serrated……………………………………………..Habiscus
6.      
   1. Leaf texture rough………………………………………………….go to 7
   2. Leaf texture smooth……………………….…………………..Brassica spp
7.      
   1. Leaf blade Lanceolate…………………….…………………..Solanum spp
   2. Leaf blade broad……………………………………………Lantana camara

3. The photography below shows four specimens labeled P, Q, R and S, which were obtained from the same animal. Examine them
   1. With reasons identify P and Q (4mks)
      P-
      Reason-
      Q-
      Reason-
   2. Based on their structure, suggest the functions of specimens P and Q (2mks)
      P-
      Q-
   3. In specimen P, name the four parts labeled A to D (4mks)
      A B C D
   4. Using observable features, state the differences between R and S (3mks)
   5. Explain how specimen S is adapted for its functions (2mks)

CONFIDENTIAL

1. X - Onion bulb ( Each student 1⁄4 )
   Y – Distilled water
   Z – concentrated sodium chloride
   
   • scalpel
   • labels
     Petri- dishes / beakers
2. Q – sukuma wiki
   K – maize leaf

MARKING SCHEME

1. You are provided with
   Spécimen X
   Solution Y
   Solution Z
   
   1. Examine the outer and inner leaves then record your observations (4mks)
      Outer leaf – papery / dry / scaly / dehydrated
      
      • Thin / membranous
      • Pigment
        Inner leaf – succulent
      • Thick
      • swollen
   2. Using a scalpel, cut and measure 6strips of 3cm length of the specimen X. Place 3 strips into a solution labeled Y, another 3 strips into a solution labeled Z. The experimental set up is allowed to stand for 20 minutes.
      
      1. What observations would be made after 20 minutes when the strips are touched (2mks)
         Strips in solution Y- feel firm / turgid / hard
         Strips in solution Z – feel soft / flabby / flaccid / tender
      2. Account for the observations recorded in (b) (i) above (4mks)
         The concentrated solution Z is hypertonic to the cell sap therefore the cell lose water by osmosis cells become flaccid / flabby.
         The distilled water (Y) is hypotonic to the cells gain water by osmosis and the strips because hard / turgid
2. You are provided with actual specimens of plant parts Q and K
   
   1.      
      1. Using external features only identify the part of the plants (2mks)
         Leaf
      2. Give three reasons for your answer in (a) (i) above (3mks)
         
         • Presence of leaf
         • Presence of midrib
         • Presence of veins
   2. With reasons state the class to which the plants from which the specimens were obtained belong (4mks)
      

      	Q	K
      Class	Dicotyledonae	monocotyledonae
      Reason	broad leaf net venation	narrow parallel

   3. State two observable features that adapt specimen Q for gaseous exchange (2mks)
      Has a broad, flat Lamina that offers a large surface area for gaseous exchange
      It is thin, thus reducing the distance over which diffusion of gases from the atmosphere to the inner most cells take place
   4. Using the dichotomous key provided, indentify the identity of the specimens Q and K in each case show the sequence; the steps in the key that you followed to arrive at the identity. (4mks)
      
      1.      
         1. Leaf parallel veined……………………………………………..go to 2
         2. Leaf net veined …………………………………………………go to 4
      2.      
         1. Leaf purple in colour…………………………..………Tradescantia spp
         2. Leaf green in colour …………………………… ……………….go to 3
      3.      
         1. Leaf with thorns on margin………………… ……………Kalanchoe spp
         2. Leaf smooth on the margin……………… ……………………Zea mays
      4.      
         1. Leaf sample………………………… …………………………….go to 5
         2. Leaf compound……………………………………………………go to 8
      5.      
         1. Leaf margin entire …………………………………………………go to 6
         2. Leaf margin serrated……………………………………………..Habiscus
      6.      
         1. Leaf texture rough………………………………………………….go to 7
         2. Leaf texture smooth……………………….…………………..Brassica spp
      7.      
         1. Leaf blade Lanceolate…………………….…………………..Solanum spp
         2. Leaf blade broad……………………………………………Lantana camara
            K 1a, 2b, 3b, - Zea mays
            Q – sukuma wiki 1b, 4a, 5a, 6b, - Brassica spp
3. The photography below shows four specimens labeled P, Q, R and S, which were obtained from the same animal. Examine them
   1. With reasons identify P and Q (4mks)
      P- Molar
      Reason
      - Biting surface is wide and has cusps / ridges
      - Presence of 3 roots
      Q - Incisor
      Reason-biting surface is chisel shaped / wedge shaped
   2. Based on their structure, suggest the functions of specimens P and Q (2mks)
      P - Grinding and crushing of food
      Q - Gripping and cutting food
   3. In specimen P, name the four parts labeled A to D (4mks)
      A cusps
      B crown
      C neck
      D root
   4. Using observable features, state the differences between R and S (3mks)
      R has a pointed biting surface while S has a broad biting surface with cusps / ridges
      R has one root while S has 2 roots
      R is smaller than S
   5. Explain how specimen S is adapted for its functions (2mks)
      It has cusps / ridges on its biting surfaces that enable crushing and grinding of food