Biology Questions and Answers - Form 2 Term 1 Mid Term Exams

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BIOLOGY
FORM 2
MID TERM
TERM 1

INSTRUCTIONS

  • Answer ALL questions in this paper

SECTION A (40 MARKS)
Answer All the questions in the space provided.

  1. Name the most appropriate tool that Biology students can use for collecting
    1. Crawling animals (1mk)
    2. Flying insects (1 mk)
  2. State the name given to the study of:
    1. Cells (1 mk)
    2. Classification of living organisms (1 mk)
  3.    
    1. Define the term species (1 mk)
    2. A Tiger is known as Panthera Tigris
      1. Identify two mistakes made in writing the scientific name (2 mks)
      2. Explain why a Leopard and a tiger cannot breed yet they belong to the same genus (1 mk)
  4. A cell was magnified 200 times using a light microscope whose eye-piece lens magnification was X10. What was the magnification of the objective lens (3 mks)
  5. The cell structure below was observed under the light microscope
    Biof2midt1q5
    1. Identify the cell structure (1 mk)
    2. Name the labeled parts A and B (2 mks)
      1.     
    3. State one function of the above structure (1 mk)
  6. In an experiment equal amounts of three different sugar solutions were placed in the risking tubings X, Y and Z. the tubings were placed in a beaker of water containing 5% sugar solution. The set up was left for two hours. The results were as shown in the diagram below.
    Biof2midt1q6
    Beginning of experiment End of experiment
    1. Name the process being investigated in the experiment (1 mk)
    2. Account for the observations made at the end of the experiment (3 mks)
    3. State three importance of the process named in (a) above in living organisms (3 mks)
  7.      
    1. Name the carbohydrates that is (3 mks)
      1. Found in abundance in mammalian blood
      2. Stored in mammalian liver
      3. Stored in plant seeds
    2. List two importance of water in living organisms (2 mks)
  8. The enzyme pepsin and trypsin are secreted as inactive precursors:
    1. What are the name of the precursors (2 mks)
    2. Why are they secreted in an inactive form (1 mk)
  9. State two structural and two environmental factors that affect the rate of transpiration
    1. Structural (2 mks)
    2. Environmental (2 mks)
  10. The diagram below is a transverse section of a certain part of a dicotyledonous plant.
    Biof2midt1q10
    1. Which part of the plant was the section made from (1 mk)
    2. Give reasons for your answer (1 mk)
    3. State the functions of the parts labeled A and C (2 mks)
      A
      C
  11. Give an example of an animal with (2 mks)
    1. Open circulatory system
    2. Closed circulatory system

SECTION B 40 MARKS

  1. The diagram below show the internal structure of a mammalian heart
    Biof2midt1q12
    1. Using arrows show the direction of blood flow in and out of the heart ( 2mks)
    2. Name the parts labeled (2 mks)
      A
      C
    3. The muscular wall of chamber D is at least three times thicker than the wall of chamber E. give a reason for this difference (1 mk)
    4. Name two special characteristics of heart muscles which distinguishes it from other parts of muscles (2 mks)
    5. In what way does the artery labeled G differ from other arteries in the body (1 mk)
  2. The figure below is a diagram of a potometer
    Biof2midt1q13
    1. What is it used for? (1 mk)
    2. State one precautions which should be taken when setting up a photometer (1 mk)
    3. The rate of transpiration was determined under normal conditions in the laboratory. Giving reasons, explain the differences you would expect if the measurements were repeated under the following conditions.
      1. The shoot is placed close to the heat source (2 mks)
      2. Some leaves are removed (2 mks)
      3. The shoot is placed in a current of air created by a fan (2 mks)
  3. The figure below is a diagram of a vertical section of a mammalian tooth
    Biof2midt1q14
    1. Name the parts labeled A – F (2 mks)
    2. How are the structures labeled A and D adapted to their functions (2 mks)
    3. List down three ways of preventing teeth diseases (3 mks)
  4.    
    1. Give two reasons why clotting of blood is important (2 mks)
    2. Name one enzyme and one metal ion that are required in the blood clotting process (2 mks)
    3. Explain why excessive bleeding may lead to death of a patient (3 mks)
    4. Explain why deficiency of vitamin K leads to excessive bleeding even from small cuts (1 mk)
  5. The diagram below illustrates an experiment to show carbon (IV) oxide is necessary for photosynthesis. The corks have been smeared with Vaseline to prevent entry of gases.
    Biof2midt1q16
    1. Why is it necessary to place the plants in the dark for two days before starting the experiment?(1 mk)
    2. What is the role of soda lime? (1 mk)
    3. Give the results you would expect if the leaves A and C were subjected to an iodine test after being in bright sunlight for 6 hours.
      A (1 mk)
      C (1 mk)
    4. Explain the results given in (C ) above (2 mks)
    5. A part from carbon (IV) oxide, name two other factors which are necessary for photosynthesis to take place (2 mks)

SECTION C 20 MARKS

  1.    
    1. The figure below is a diagram of an intestinal villus. Study it and answer the questions that follow.
      Name the parts labeled A – D (2 mks)
    2. What is the importance of the villi? (1 mk)
    3. What is the function of the part labeled F (1 mk)
    4. Most of absorption of digested food in mammals takes place in the ileum. In what ways is it adapted for this function (4 mks)
    5. Name two nutrients that are absorbed in mammalian gut without chemical digestion (2 mks)
  2. State and Explain five factors that determine energy requirements in human beings (10 mks)

MARKING SCHEME

SECTION A (40 MARKS)
Answer All the questions in the space provided.

  1. Name the most appropriate tool that Biology students can use for collecting
    1. Crawling animals (1mk) - Pitfall trap √ (1)
    2. Flying insects (1 mk) - Sweep net √ (1)
  2. State the name given to the study of:
    1. Cells (1 mk) - Cytology √ (1)
    2. Classification of living organisms (1 mk) - Taxonomy √ (1)
  3.    
    1. Define the term species (1 mk)
      Species is the smallest unit of classification, whose members can naturally/freely interbreed to give rise to viable/fertile offspring’s. √ (1)

    2. A Tiger is known as Panthera Tigris
      1. Identify two mistakes made in writing the scientific name (2 mks)
        The second name which represents species should start with a small letter. √ (1)
        The two names should be underlined separately √ (1)

      2. Explain why a Leopard and a tiger cannot breed yet they belong to the same genus (1 mk)
        Because they do not belong to the same species. Only members of the same species can breed to give rise to offsprings.

  4. A cell was magnified 200 times using a light microscope whose eye-piece lens magnification was X10. What was the magnification of the objective lens (3 mks)
    Total magnification = eye piece lens magnification X objective lens magnifications
    Therefore
    Magnification of objective lens=Total magnificationMagnification of eye piece lens√ (1)
    X200X10=X20
  5. The cell structure below was observed under the light microscope
    Biof2midt1q5
    1. Identify the cell structure (1 mk)
      Cell membrane/plasma membrane √ (1)

    2. Name the labeled parts A and B (2 mks)
      1. - Phospholip layer √ (1)    
      2. - Protein layer √ (1)
    3. State one function of the above structure (1 mk)
      • It encloses the contents of the cell √ (1) either
      • It allows selective movement of particles in and out of the cell √ (1)

  6. In an experiment equal amounts of three different sugar solutions were placed in the risking tubings X, Y and Z. the tubings were placed in a beaker of water containing 5% sugar solution. The set up was left for two hours. The results were as shown in the diagram below.
    Solubility Experiment
    1. Name the process being investigated in the experiment (1 mk)
      Osmosis √ (1)

    2. Account for the observations made at the end of the experiment (3 mks)
      • The solution in tubing X was more dilute thatn that in the beaker/solution in tubing X is hypotonic to be solution in to beaker √ (2). Water moved from the tubing into the beaker by osmosis/. Water molecules moved from the beaker where they are highly concentrated to where they are lowly concentrated. √ ( ½)
      • The solution in tubing Y had the same concentration as that in the beaker. The solution is isotonic. There is no movement of water in either direction.
      • The solution in tubing Z was more concentrated that in the beaker or Z is hypertonic √ (½) to the solution in the beaker √ .
      • Water molecules moved from the beaker where take √ are more conc into the tubing by osmosis. Or in the beaker there are more free water molecules than in the tubing Z. free water molecules more from the beaker to the risking tubing through osmosis.

    3. State three importance of the process named in (a) above in living organisms (3 mks) 
      • Uptake of water from the soil into the root hairs of plant roots √ (2).
      • Uptake of water from the surrounding medium into the cells of microorganisms.
      • Transport of water from the epidermal cells of the root to the cells at the centre of the root (support).
      • Reabsorption of water from the kidney tubules (osmoregulation)
      • Reabsorption of tissue fluid into the bloodstream at the veneous of the capillaries.
      • Movement of H2O from the veins of leaves through the leaf cells to the atmosphere during transpiration.
      • Opening and closing of stomata.
      • Feeding insectirorous plants.
           
    1. Name the carbohydrates that is (3 mks)
      1. Found in abundance in mammalian blood - Glucose
      2. Stored in mammalian liver - Glycogen
      3. Stored in plant seeds - Starch

    2. List two importance of water in living organisms (2 mks)
      • Act as a solvent in which all biology reactions take place
      • It is a reactant in many biological reactions e.g. photosynthesis, hydrolysis of food molecules such as carbohydrates, fats and proteins.
      • It is a solvent in which transport of nutrients, gases and waste products takes place.
      • It is the solvent in which raw materials like minerals salts and finished products like sucrose are transported in plants.
      • Helps in maintenance of constant body temperature in warm blooded animals because of its high specific heat capacity.
      • It is responsible for turgidity of plant cells and hence the maintenance of an erect posture of plant.
      • It is a habitat for many plants and animals.

  7. The enzyme pepsin and trypsin are secreted as inactive precursors:
    1. What are the name of the precursors (2 mks)
      Pepsinogen and trypsinogen

    2. Why are they secreted in an inactive form (1 mk)
      If secreted in active form, they would digest the cells which they are formed and also the lining of the glands that secret.

  8. State two structural and two environmental factors that affect the rate of transpiration
    1. Structural (2 mks)
      • Thickness of cuticle (rej. Cuticle alone)
      • Leaf size and shape
      • Location of the stomata/position
      • Number of stomata & size
      • Leaf fall
      • Hairly leaves

    2. Environmental (2 mks)
      • Environmental
      • Temperature
      • Light intensity
      • Wind
      • Atmospheric pressure
      • Humidity
      • availability of water

  9. The diagram below is a transverse section of a certain part of a dicotyledonous plant.
    Biof2midt1q10
    1. Which part of the plant was the section made from (1 mk)
      Young root √ (1)

    2. Give reasons for your answer (1 mk)
      • Presence of starshaped xylem with phloem strands lying between the arms of the star √.
      • Presence of root hairs

    3. State the functions of the parts labeled A and C (2 mks)
      A - Increases the surface areas for absorption of water, mineral salts and gases √.
      C - Transport of water and dissolved minerals to the stem and the leaves √ (1).
  10. Give an example of an animal with (2 mks)
    1. Open circulatory system - Arthropods e.g insects any correct
    2. Closed circulatory system -  mammals etc

SECTION B 40 MARKS

  1. The diagram below show the internal structure of a mammalian heart
    Biof2midt1q12
    1. Using arrows show the direction of blood flow in and out of the heart ( 2mks)
      Biof2midt1a12
    2. Name the parts labeled (2 mks)
      A - Aorta √ (1)
      C - Semilunar valves √ (1) (at the base of the aorta)
    3. The muscular wall of chamber D is at least three times thicker than the wall of chamber E. give a reason for this difference (1 mk)
      Because D (left ventricle) has to pump blood all over the body whereas E (right ventricle) only pumps blood to the lungs. (Thicker walls helps D to exert pressure to force blood all over the body) √ (1)

    4. Name two special characteristics of heart muscles which distinguishes it from other parts of muscles (2 mks)
      • They have inherent contractility i.e they contract on their own without stimulation of nerve or hormones (myogenic) √ (1)
      • They can contract rhythmically throughout without fatigue

    5. In what way does the artery labeled G differ from other arteries in the body (1 mk)
      (pulmonary artery) carries deoxygenated blood from the right ventricle to the lungs √ (1).

  2. The figure below is a diagram of a potometer
    Biof2midt1q13
    1. What is it used for? (1 mk)
      To estimate the rate of transpiration by measuring the rate of water uptake by a plant shoot.

    2. State one precautions which should be taken when setting up a photometer (1 mk)
      • Stem of the shoot should be cut and fixed into to potomoter under water to prevent air entering into the xylem vessels. 
      • All joints should be water tight √ (1)


    3. The rate of transpiration was determined under normal conditions in the laboratory. Giving reasons, explain the differences you would expect if the measurements were repeated under the following conditions.
      1. The shoot is placed close to the heat source (2 mks)
        The rate of transpiration would increase √ (1). Because heat causes temperature to increase hence increasing the rate of evaporation √ (1) of water from mesophyll cells of the leaf and reduces relative humidy of the air outside the leaf √ (1).

      2. Some leaves are removed (2 mks)
        Rate would decrease √ (1). Because removal of the leaves reduces the surface available for transpiration √ (1).

      3. The shoot is placed in a current of air created by a fan (2 mks)
        Rate would increase √ (1). Because moving air washes away layers of water vapour √ (1) immediately outside the leaf. This lowers humidity of air outside the leaf thus increasing the relative humidity difference (saturatiry deficit) between the inside and outside of the leaf.

  3. The figure below is a diagram of a vertical section of a mammalian tooth
    Biof2midt1q14
    1. Name the parts labeled A – F (2 mks)
      1. Enamel √ 
      2. Gum √ (1) 
      3. Dentine √ (1)
      4. Pulp cavity √ 
      5. Cement √
      6. Peridontal ligament

    2. How are the structures labeled A and D adapted to their functions (2 mks)
      A – it is made up of hard organic substance consisting of mineral salt crystals (calcium sulphate) and carbonate) board together by keratin √ (1). It forms an efficient, hard biting surface.
      D – Contains blood vessels provide nourishment for the dentine √ (1)/Nerve endings for sensibility of the tooth √ (1)

    3. List down three ways of preventing teeth diseases (3 mks)
      Regular brushing
      Avoiding very sugarly food
      Proper exercise of the teeth by eating tough fibrous food e.g. carrots, maize and vegetables.
      Eating food rich in vitamin C
      Regular dental checkup

  4.    
    1. Give two reasons why clotting of blood is important (2 mks)
      Prevent loss of blood √ (1)
      Prevent entry of disease causing micro-organism √ (1)

    2. Name one enzyme and one metal ion that are required in the blood clotting process (2 mks)
      Enzymes – Thromboplastin √ (1)/ Thrombin √
      Ion: Calcium ions (Ca2+) √ (1)

    3. Explain why excessive bleeding may lead to death of a patient (3 mks)
      • Excess bleeding causes a decrease in blood volume √ (1) leading to reduction in the total number of circulating red blood cells √ (1) and hence a deficiency of oxygen supply √ (1) to tissues. There is also reduction of nutrients supply since some dissolved substances are lost. Tissues also get dehydrated √ (1) reducing their metabolic activity.

    4. Explain why deficiency of vitamin K leads to excessive bleeding even from small cuts (1 mk)
      Vit. K is necessary for the formation of a protein called prothrombin √ (1) in the liver. Which is important factor in the blood clotting process.

  5. The diagram below illustrates an experiment to show carbon (IV) oxide is necessary for photosynthesis. The corks have been smeared with Vaseline to prevent entry of gases.
    Biof2midt1q16
    1. Why is it necessary to place the plants in the dark for two days before starting the experiment?(1 mk)
      To remove all starch from the leaves (To destarch the leaves) √ (1)

    2. What is the role of soda lime? (1 mk)
      To absorb carbon (IV) Oxide √ (1)

    3. Give the results you would expect if the leaves A and C were subjected to an iodine test after being in bright sunlight for 6 hours.
      A (1 mk)- would be stained brown √ (1)
      C (1 mk)-Would be stained blue – black √ (1)
    4. Explain the results given in (C ) above (2 mks)
      Leaf A was deprived off carbon (IV) Oxide, √ (1) which prevented photosynthesis from taking place.
      Leaf C had access to carbon (IV) Oxide; √ (1) photosynthesis took place

    5. A part from carbon (IV) oxide, name two other factors which are necessary for photosynthesis to take place (2 mks)
      • Water
      • Light

SECTION C 20 MARKS

  1.    
    1. The figure below is a diagram of an intestinal villus. Study it and answer the questions that follow.
      Name the parts labeled A – D (2 mks)
      Biof2midt1q17
      1. – Microvilli 
      2. – Lacteal
      3. – Venule
      4. – Arteviole

    2. What is the importance of the villi? (1 mk)
      To provide a large surface area for the digestion and absorption of food

    3. What is the function of the part labeled F (1 mk)
      is network of capillaries where soluble end products of digestion diffuse into the blood stream

    4. Most of absorption of digested food in mammals takes place in the ileum. In what ways is it adapted for this function (4 mks)
      • It is very long and the inner lining is highly folded offering a large surface area for absorption.
      • Its surface area is increased further by villi and microvilli.
      • Its epithellum is very thin allowing soluble food materials to pass through faster.
      • It is richly supplied with blood capillaries and lacteals for transport of absorbed food materials.

    5. Name two nutrients that are absorbed in mammalian gut without chemical digestion (2 mks)
      • Vitamins (any)
      • Inorganic ions

  2. State and Explain five factors that determine energy requirements in human beings (10 mks)
    1. Basal metabolism √ (1).
      This is the energy required to maintain life it includes the energy used to drive vital processes as blood circulation, breathing maintenance of body temp etc. or basal metabolic rate (BMR). This is the lowest level of energy production √ (1).
    2. Sex √ (1) 
      Males require more energy than females because males are more muscliline than female. Females have more fats males use more energy compared to females.
    3. Body size √ (1) explanation √ (1)
      Small bodies people have a small volume which leads to a large surface area to volume ratio. Their bodies lose a lot of heat to the surrounding. They therefore require more energy than big bodied people who have small surface area to volume ratio.
    4. Occupation/activity √ (1) –
      manual workers require more energy than for example an office worker (any correct explanation by use of an example)
    5. Age √ (1) explanation √ (1)
      Young children have many actively dividing cells and they are physically active. Therefore their Basal metabolic rate is higher than that of adults.

 


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