Biology Paper 2 Questions and Answers - Joint Pre-Mock Exams 2021/2022

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Instructions to candidates;

  • Answer ALL questions in section A.
  • In section B, answer question 6 (compulsory) and either question 7 or 8.
  • Candidates should answer the questions in English.


  1. A common species of rats has individuals with white, black or grey coats. During a study, a rat with white coat was crossed with a rat with black coat. Both parents were pure lines. All the off springs in F1 generation had grey coats. Using letter B to represent the gene for black coat and W for white coat, answer the questions that follow.
    1. Work out the phenotypes of the F1 generation. (4marks)
    2. Give a genetic explanation of the nature of off springs in the F1 generation. (1mark)
    3. State the significance of a Test cross in the study of genetics. (1mark)
    4. State the importance of crossing over in meiosis. (1mark)
    5. Name one example of a characteristic in man that is transmitted by multiple alleles. (1mark)
  2. The diagram below shows some of the processes that take place in a female reproductive system.
           Bio Joint PM PP2 Q2 2122
    1. Name process labeled; (1mark)
      I. ……………………………………
    2. Name structures labeled; (2marks)
      T. ……………………………………….
      R. ……………………………………….
    3. Identify hormones responsible for formation of structures. (2marks)
      T. ………………………………………….
      R. ………………………………………….
    4. Explain what leads to process at II. (3marks)
  3. A group of students set up the apparatus below to investigate a physiological process. Temperature changes were recorded for a period of one week.
            Bio Joint PM PP2 Q3 2122
    1. State the observation made in temperature reading in flask X (1 mark)
      Give a reason (2marks)
    2. Why are micro-organisms killed in boiled beans? (1mark)
    3. Give a reason as to why the flasks were not fully filled with seeds (1mark)
    4. Why were flasks inverted upside down? (1mark)
    5. Why is the experiment carried out in a vacuum flask? (1mark)
    6. What alteration would be made in the set up to make the results more reliable? (1mark)
  4. Gastrin is a hormone produced by mammals.
      1. Where is the hormone produced. (1mark)
      2. What is the function of gastrin? (1mark)
    2. What stimulates the production of gastrin? (1mark)
    3. The diagram below shows part of the human intestine.
            Bio Joint PM PP2 Q4 c 2122
      1. Identify the parts labeled A and B. (2marks)
      2. To which circulatory system does the part labeled B belong. (1mark)
    4. State any two adaptations of the human large intestine to its function. (2marks)
  5. The diagram below represents part of a xylem tissue.
        Bio PP2 Q5 JPM
      1. Name the parts labeled P and Q. (2marks)
        P ………………………………………………………………………………
        Q ………………………………………………………………………………
      2. Give the function of the part labeled P. (1mark)
    2. State the function of the phloem tissue. (1mark)
      1. State how the functioning of the phloem tissue is affected if the companion cell is destroyed. (1mark)
      2. Give a reason for your answer. (1mark)
    4. State any two structural differences between phloem and xylem tissues. (2marks)

Answer question 6 (Compulsory) and either question 7 or 8 in the spaces provide after question 8.

  1. Two species of parasitic wasps X (Vespula vulgaris) and Y (Vespula acadica) were introduced in an orchard in order to control to control the population of aphids. The numbers of each species of wasps were counted at two-month intervals and recorded. The table below shows the population of the two wasps over a 18-month period in the orchard.
     Time     0   2   4   6   8   10   12   14   16   18

     Species X   400   1000   2800   4400   5400   6000   6400   6400   6200   6400 
       Species Y   400  1800  2400  2200  1800  1400  800  600  400  600
    1. Plot a graph of wasps against time on the grid provided. (7marks)
    2. State the type of relationship between the two wasp species. (1mark)
    3. Account for the differences in population of the two wasp species between:
      1. 0 – 3 years (3marks)
      2. 4 – 14 years (3marks)
    4. The experiment was continued for another 8 months. On the 18th month the population of species X increased and surpassed that of Y. account for this observation. (3marks)
    5. Explain how the population of the wasps was determined. (3mks)
  2. Describe the role of the following organs in excretion and homeostasis.
    1. The liver (10 marks)
    2. The skin during hot environmental conditions (10 marks)
  3. Discuss the various evidences, which show that evolution has taken place. (20marks)


    1. Parents’                               ♂                 ♀
      Parental phenotype        black coat     white coat
      Parental genotypes         BB x WW ;
      Gametes                         Bio Joint PM PP2 Ans 1 2122
      Phenotypes – all grey ;
    2. Incomplete dominance/ partial dominance;
    3. To establish the genotypes of the off springs/organism;
    4. Results in new gene combination/recombination; causing variations/hybrid vigour;
    5. Blood groups;
    1. I – ovulation;
    2. T – Graafian follicle;
      R – Corpus luteum;
    3. T – follicle stimulating hormone;
      R – Luteinizing hormone;
    4. (When sperm comes into contact with egg)
      • Acrosome bursts open and releases lytic enzymes which dissolve egg membrane;
      • Acrosome then turns inside -out forming a fine filament that penetrates the egg; 
      • Head of sperm enters ovum, tail is left outside the ovum;
      • Vitelline membrane undergoes chemical reorganization which stops any other sperm from entering ovum; once in cytoplasm head burst releasing male nucleus which then fuses with female nucleus to form a diploid zygote;
    1. A rise in thermometer reading/Increased temperatures; (Rise in Temperature)
      • During germination seeds use oxygen for respiration; to produce energy, some in heat form; hence rise in temperature.
    2. To prevent bacterial respiration hence heat production;
    3. For easier circulation of air within the flask;
      • To prevent heat loss; (warm air is less dense rises up in the flask)
      • To allow carbon (IV) oxide to escape because it is denser than air.
    5. Conserve heat; / to prevent heat loss or heat gain
    6. Use a thermometer with a narrower capillary bore.
      1. Walls of stomach;
      2. Stimulates the secretion / production of gastric juice; √
    2. Presence of food in the stomach;
      1. A – Blood capillaries; REJ CAPILLARY B – Lacteal;
      2. Lymphatic system
      • Produces plenty of mucus to lubricate coarse/indigestible material during peristalsis;
      • Wide human accommodates /store indigestible food
      • Elongated to increase surface are for absorption of water.
      • has muscles to enable peristalsis when they contract;
      1. P – Tracheids Q – pits
      2. P- water conduction
    2. Function of phloem – translocation/ transport of organic substances from the leaves to the rest of the plant;
      1. Translocation of food will not occur acc. Slow translocation
      2. Reason – it is the companion cell that contains numerous mitochondria which provide adequate energy for translocation;
       Phloem    Xylem 
       1) Made of living cells
       2) Have companion cells
       3) Have cytoplasmicstrands
       4) Lack lignin deposits 
      - made of dead cells 
      - lack companion cells
      - lack cytoplasmic strands
      - have lignin deposits;       (any2x1=2mks) 
    1. Graph of population against time
      Bio PP2 Ans 6a JPM
    2. Competition; Accept parasitism
      1. Both populations increase; due to more food and hence less (interspecific) competition for space and food; the increase in population of species Y is higher/ faster than that of X; Y has a shorter life cycle than X; Y has faster growth and maturity rate than X; Y lays more eggs/ has faster reproduction rate than X;
      2. Population of X is higher than that of Y; population of X increases with increase in time; population of Y decreases with increase in time; X is a better competitor for food; X has a longer life expectancy/ span than Y; X could be parasitic on Y; a disease infestation that only affects Y;
    4. Another organism predatory to X migrated or were introduced into the orchard; X migrated out of the habitat; spraying of the orchard with a pesticide/ chemical that kills X; high explosion on the number of aphids so no competition for food;
    5. Capture recapture method; as many wasps as possible were caught; marked and counted; the number was recorded as first marked; the exercise was repeated 24 hours later; as many wasps as possible were caught; their number counted and recorded as second capture; the number of wasps in the second capture that had the original mark was determined and recorded as marked recapture; the population was calculated as;
      Population = First marked x Second capture;
                                 Marked recapture
  7. Describe the role of the following organs in excretion and homeostasis. 
    1. The liver (10 mks)
      • Regulation of blood sugar; when blood sugar is below normal/90mg/100cm3glucagon; Stimulates/triggers the conversion of glycogen to glucose in the liver/by the liver cells/hepatocytes; the glucose is released into the blood stream; Glucose level returns to normal; When the blood sugar is in excess/above normal/90mg/100cm3, insulin; causes/triggers/stimulates the liver cells to covert glucose to glycogen/fats which is stored; by increasing the rate of metabolic activitie,energy is produced; Excretion of bile pigments/biliverdin and bilirubin produced due to breakdown of worn out red blood cells; deamination/removal of amino group from excess amino acids to form urea; and detoxification/poisonous substances are made harmless/less toxic;    Max 10
    2. The skin during hot environmental conditions (10 mks)
      • Sweat glands excrete urea; excess water and salts; hence maintaining salt and water balance in the blood/osmoregulation; evaporation of sweat; cools the body due to loss of latent heat of vaporization; when the body temperature rises above normal; blood vessels in the skin vasolidate; allowing more blood to flow near the skin surface; thus heat is lost to the environment by radiation/convection;Erector pili muscles relaxes; hair on the skin surface flattens/lie flat; reducing insulation/trapping less air; hence heat is lost from the body by radiation/convection;  Max 10
    1. Fossils records.
      • Fossils are preserved remains of ancestral forms that lived long time ago mainly formed from preserved hard parts found on sedimentary rocks; when fossils of related organisms are arranged in chronological order which is made possible by carbon dating, they from form fossils records which reveal trends in evolution overtime in the organism concerned; this gives direct evidence of the type of organism that existed at certain geological algae.
    2. Geographical distribution of organisms.
      • The theory of continental drift supposes that at some time the present day continents were one single landmass which later drifted apart; closely related organisms were separated and isolated from one another thus evolving differently which leads to formation of different species through natural selection; each set of organism adapted to different set of environmental conditions eg. Camels in Africa and illama in South America.
    3. Comparative embryology.
      • Embryology is the study of formation and development of an embryo. The embryos of different vertebrate groups (fish, birds, amphibians, reptiles and mammals) are morphologically similar during the early stages of development; This relationship is as a result of their common ancestry. The closer the resemblance between the early stage embryos, the closer is their evolutionary relationship; this theory is called recapitulation theory.
    4. Comparative anatomy
      • This is comparing the form and structures of different organisms in those organisms which show similarities suggest that they have a common or related ancestry; Adaptive radiation is where the divergent forms originating from a single ancestral form may become adapted to different ecological niche in a given habitat; Homologous structures are those parts that have a common embryonic origin but may be modified to perform different functions ;e.g. the forelimb of a bat is modified to form a wing for flight, the forelimb of a horse is elongated to enhance speed in running.
      • Analogous structures are those structures that have different embryonic origin but have evolved to perform similar functions due to the exploitation of the same kind of environment; Examples of analogous structure are wings of birds and those of insects have different embryonic origin but both are adapted for flight.
        Vestigial structures are those structures that have in the course of time ceased to be functional and therefore have become reduced in size or rudimentary; eg coccyx in humans, nictitating membrane in the eye of the mammals.
    5. Comparative serology
      • Experiments with serum (serological tests) are used to show phylogenetic relationships e.g. If human serum is injected into a rabbit, the proteins in the serum act as antigens. The rabbit produces antibodies against the human proteins. When blood with antibodies is drawn from the rabbit and mixed with serum from different animals, an immunological reaction occurs forming a precipitate. The amount of precipitate formed varies from one animal to the other. The greater the amount the closer the phylogenetic relationship between the animal and the human being; the lesser the precipitate shows that few or no antigen is common in organism hence are far apart i.e no common ancestry;
    6. Cell biology
      • The cells of all higher organisms show basic similarities in their structure and functions. Thus all these cells contain cell membranes and organelles such as ribosome, Golgi bodies, and mitochondria;
      • They also have some biological chemicals in common e.g. ATP and DNA. This strongly indicates that all cell types have a common ancestral origin;
      • Also plant cells contain cellulose cell wall, cell sap, chloroplast etc. all these features are absent in animal cells.Among animals blood pigments are of universal occurrence. These include haemoglobin (vertebrates and invertebrates), haemocyanin (moluscs and crustaceans) and chlorocruorin (annelids).

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