Biology Questions and Answers - Form 3 Mid Term 1 Exams 2022

Questions

1. A student caught an animal which had the following characteristic.
   Body divided into two parts
   Simple eyes
   Eight legs
   The animal belongs to class ________________(1mk)
2. What is the function of the following cell organelles?
   
   1. Golgi apparatus. (1mk)
   2. Ribosomes (1mk)
3. Why is oxygen important in the process of active transport in cells? (2mks)
4. What happens to red blood cells when placed in concentrated solution? (2mks)
5. Why is it that xylem vessels do not collapse even when they do not contain water (1mk)
6. Below is a dental formula of a given animal
     i     c      pm    m
    0     0        3     3
    3     0        3     3
   With reasons identify the mode of feeding (3mks)
   Reason:
7. The chart below shows a feeding relationship in a certain ecosystem.
   
   
   1. Construct two food chains ending with a tertiary consumer in each case (2mks)
   2. Which organism has the largest variety of predators in the food web (1mk)
   3. Name secondary consumers in the food web (2mks)
   4. Suggest three ways in which the ecosystem would be affected if there was prolonged droughts (3mks)
8.       
   1. Distinguish a community and population (2mks)
   2. Explain how birds of prey are adapted to obtaining their food (2mks)
9.     
   1. Name the bacteria found in root nodules of leguminous plants (2mks)
   2. What is the role of the bacteria named in (i) above (1mk)
10. In a fish pond the number of fish was estimated by use of the following information
    First capture =50
    Second capture =90
    Marked captured =25
    1. Identify the method suggested above (1mk)
    2. Name two other sampling methods used in estimating populations (2mks)
    3. Calculate the total number of fish in the pond (2mks)
    4. Give three assumptions in the above methods (3mks)
11. A person was found to pass out large volumes of dilute urine frequently (2mks)
    Name the:
    1. Disease the person was suffering from.
    2. Hormone that was deficient.
12. State two ways by which Acquired Immune deficiency Syndrome (AIDS) virus is transmitted. (2mks)
13.       
    1. Name the causative agents of the following diseases in humans. (2mks)
       1. Typhoid
       2. Amoebic dysentery
    2. Name the disease caused by Plasmodium falciparum (1mk)
14.       
    1. Describe three effects of dumping untreated sewage into a river. (3mks)
    2. Name one process that is responsible for loss of energy from one trophic level to the next. (1mk)
15. Using a microscope, a student counted 55 cells across a field of view whose diameter was 600 cm.
    Calculate the average length of cells. Show your working. (2mks)
16. Name two structures used for gaseous exchange in plants. (2mks)
17.            
    1. Name the class in the phylum arthropod which has the largest number of individuals. (1mk)
    2. State three external differences between chilopoda and diplopoda (3mks)
18. Explain how you would estimate the population of fish in a bond. (3mks)

Marking Scheme

1. A student caught an animal which had the following characteristic.
   Body divided into two parts
   Simple eyes
   Eight legs
   The animal belongs to class?
   • Arachnida
     
     
2. What is the function of the following cell organelles.
   1. Golgi apparatus. (1mk)
      • Packaging and transportation of glycoproteins
        
        
   2. Ribosomes (1mk)
      • Site for proteins synthesis
        
        
3. Why is oxygen important in the process of active transport in cells? (2mks)
   • Oxygen is required for respiration thus producing energy for active transport
     
     
4. What happens to red blood cells when placed in concentrated solution. (2mks)
   • Red blood cells loose water to the solution by osmosis shrink and become crenated
     
     
5. Why is it that xylem vessel do not collapse even when they do not contain water (1mk)
   • Their tissue walls are lignified
     
     
6. Below is a dental formula of a given animal
   With reasons identify the mode of feeding (3mks)
   Reason:
   • Herbivorous
     No canine and incisor on the upper jaw.
     
     
7. The chart below shows a feeding relationship in a certain ecosystem.
   1. Construct two food chains ending with a tertiary consumer in each case (2mks)
      • Green plants → Grasshoppers → Lizards → Domestic cats
      • Green plants → Mice → Snakes → Hawk
      • Green Plants → Mice → Snakes → Domestic cats
        
        
   2. Which organism has the largest variety of predators in the food web (1mk)
      • Mice
        
        
   3. Name secondary consumers in the food web (2mks)
      • Lizards, Domestic cats, Hawks, Snakes.
        
        
   4. Suggest three ways in which the ecosystem would be affected if there was prolonged droughts (3mks)
      • Most plants will die/dry
      • Some organisms may starve to death
      • Some organisms may migrate in search of food and shelter.
8.            
   1. Distinguish a community and population (2mks)
      • A community consists of all living organisms of different species in a habitat interacting with each other while a population consists of organisms of a given species in a given area over a given period of time.
        
        
   2. Explain how birds of prey are adapted to obtaining their food (2mks)
      • Have curved/strong/sharp claws for grabbing/holding prey
        
        
9.                 
   1. Name the bacteria found in root nodules of leguminous plants (2mks)
      • Rhizobium
        
        
   2. What is the role of the bacteria named in (i) above (1mk)
      • Convert nitrogen into nitrates.
        
        
10. In a fish pond the number of fish was estimated by use of the following information
    First capture =50
    Second capture =90
    Marked captured =25
    1. Identify the method suggested above (1mk)
       • Capture recapture method.
         
         
    2. Name two other sampling methods used in estimating populations (2mks)
       • Line transect
       • Belt transect
       • Quadrat method
         
         
    3. Calculate the total number of fish in the pond (2mks)
       • 180 fish
         
         
    4. Give three assumptions in the above methods (3mks)
       • The time period is enough for the organisms to mix uniformly.
       • The markings do not come off or affect the behavior of the organisms.
       • The population does not vary within the period of study due to death or birth.
       • No migration or immigration of organisms.
         
         
11. A person was found to pass out large volumes of dilute urine frequently (2mks)
    Name the:
    1. Disease the person was suffering from
       • Diabetes Inspidus.
         
         
    2. Hormone that was deficient.
       • Antidiuretic hormone
         
         
12. State two ways by which Acquired Immune deficiency Syndrome (AIDS) virus is transmitted. (2mks)
    • Unprotected sexual intercourse with infected persons.
    • HIV mother breastfeeding.
    • Sharing of sharp/piercing objects with infected persons.
13.        
    1. Name the causative agents of the following diseases in humans. (2mks)
       1. Typhoid
          • Salmonella typhi
            
            
       2. Amoebic dysentery
          • Entamoeba histolytica
            
            
    2. Name the disease caused by Plasmodium falciparum (1mk)
       • Malaria
         
         
14.          
    1. Describe three effects of dumping untreated sewage into a river (3mks)
       • Leads to eutrophication
       • Kill organisms in water
       • Causes water borne disease e.g. cholera
       • Changes the water pH.
       • Reduces the quality of water for consuming.
         
         
    2. Name one process that is responsible for loss of energy from one trophic level to the next (1mk)
       • Respiration
       • Excretion
       • Defecation
         
         
15. Using a microscope, a student counted 55 cells across a field of view whose diameter was 600 cm.
    Calculate the average length of cells. Show your working. (2mks)
    • Length of one cell = 109.09µm
      
      
16. Name two structures used for gaseous exchange in plants. (2mks)
    • Stomata
    • Lenticels
    • Pneumatophores
17.                 
    1. Name the class in the phylum arthropod which has the largest number of individuals. (1mk)
       • Class insecta0
         
         
    2. State three external differences between chilopoda and diplopoda. (3mks)
       

       Chilopoda	Diplopoda
       Pair of walking legs per segment	Two pairs of legs per segment
       Has poisonous claws	Lack poisonous claws
       Body dorsal ventrally flattened	Cylindrical body
       Body divided head and trunk	Body divided into head thorax and trunk

18. Explain how you would estimate the population of fish in a bond. (3mks)
    • Identify the area of study using a fish net, capture the fish, mark and release. Allow the fish to mingle for 24 or 72 hours. Capture again and identify the marked recaptured.