Home Teachers' Resources FORM 3 BIOLOGY PP2 END TERM 2 EXAMS PLUS MARKING SCHEMES

FORM 3 BIOLOGY PP2 END TERM 2 EXAMS PLUS MARKING SCHEMES

FORM 3  BIOLOGY PAPER 2 

END OF TERM 2

Answer all the questions in SECTION A in the spaces provided.

  • In section B answer question 6 (Compulsory) in the spaces provided and either question 7 or 8 in the space provided after question 8.

 

SECTION A (40MKS)

  1. The two cells shown below are obtained from two different potato cylinders which were immersed in two different solutions P and Q.

 

  • (i) Name the structures labelled A and C     (2mks)

 

A         –

 

B         –

 

 

(ii)       State the function of structure B. (1mk)

 

 

 

 

  • Suggest the identity of the solution Q (1mk)

 

 

 

  • Account for the change in Cell 1 above (2mks)

 

 

 

 

  • State two importance of the physiological process being demonstrated above in living organisms. (2mks)

 

  1. Study the following food web and answer the questions that follow.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  • (i) Name the organisms that occupy the second trophic level (2mks)

 

 

 

(ii)       What is the other name for the second trophic level (1mk)

 

 

 

  • Write down two food chains from the web that
  • End with hawks as tertiary consumer (1mk)

 

 

 

  • End with hawks as Quaternary consumer. (1mk)

 

 

 

 

  • Giving reasons state;
  • The organism with largest biomass (1mk)

 

 

 

 

  • The organism with least biomass (1mk)

 

 

 

 

 

  • Name the source of energy in the above ecosystem. (1mk)

 

 

 

  1. The diagram below represents a longitudinal section through the ileum wall.

 

 

 

 

 

 

 

 

 

 

 

 

  • Identify the structure labeled A and B (2mks)

 

A         –

 

B         –

 

  • State one function of A and B (2mks)

 

A         –

 

B         –

 

  • State two functions of the ileum. (2mks)

 

 

 

 

  • Explain the role of the liver in digestion. (2mks)

 

 

 

 

  1. The equation below represents a metabolic process that occurs in a certain organ in the mammalian body.

 

Ammonia                  enzymes                                    Organic compound Q + water

Carbon (IV) Oxide

 

 

  • Name the process represented in the equation. (1mk)

 

 

 

  • Name the organ in which the process occurs. (1mk)

 

 

 

  • Why is the process important to the mammal? (1mk)

 

 

 

 

  • Identify the organic compound Q. (1mk)

 

 

 

 

  • What happens to organic compound Q ? (1mk)

 

 

 

 

  • A person was found to pass large volume of dilute urine frequently. Name the;      (3mks)

 

  • Disease the person was suffering from.

 

 

 

  • Hormone that was deficient.

 

 

 

  • The gland that secretes the above hormone.

 

 

 

 

  1. Some glucose was boiled and cooled in a boiling tube. Some yeast was added and a layer of oil put on top. The set up below was used.

 

 

 

 

 

 

 

 

 

 

 

 

 

  • Why was the glucose solution boiled before the experiment. (1mk)

 

 

 

 

 

 

  • What is the use of the oil film in the experiment ? (1mk)

 

 

 

 

  • Name the process being investigated by the above experiment. (1mk)

 

 

 

 

  • State what happens to the lime water as the experiment proceeds to the end. (1mk)

 

 

 

 

  • Explain what would happen if the temperature of glucose and yeast was raised beyond 450 (2mks)

 

 

 

 

 

  • State two industrial applications of the process being investigated above in the experiment. (2mks)

 

 

 

 

 

 

 

SECTION B (40MKS)

Question 6 (Compulsory) and either question 7 or 8.

 

  1. In an ecological study, a locust population and that of crows was estimated in a grassland area over a period of one year. The results were tabulated as shown below:-

 

Months J F M A M J J A S O N D
Number of locusts 90 20 11 25 200 450 652 15 10 35 192 456
Number of crows(birds) 4 2 0 1 8 16 22 2 1 1 5 15
Amount of rainfall 20 0 55 350 520 400 350 10 25 190 256 350

 

  • Draw a graph of population of locusts and crows (birds) against time. (8mks)

 

 

  • (i) State the relationship between rainfall and locust population. (1mk)

 

 

 

 

(ii) Account for the relationship you have stated in (b) (i) above (1mk)

 

 

 

 

  • What happens on the populations of locusts and crows in the months of January to

March ? Give a reason. 2mks)

 

 

 

 

 

  • State one method used to estimate the population of locust. (1mk)

 

 

 

 

  • (i) State the trophic level of the;             (2mks)

 

Locusts           –

 

 

 

Crows              –

 

 

 

(ii)       Construct a simple complete food chain involving these organisms (2mks).

 

 

 

 

 

 

 

 

 

  • If the locusts were removed from the food chain, what would be its effect ? (1mk)

 

 

 

 

 

  • Define the following terms (2mks)

 

(i)Biomass

 

 

 

(ii)Ecosystem

 

 

 

 

 

 

  1. Describe how hydrophytes and xerophytes are adapted to deal with environmental problems in the regions where they grow. (20mks)

 

 

  1. Describe how the mammalian skin regulates body temperature.(20mks)



 

FORM 3  BIOLOGY PP 2  MARKING SCHEME

END OF TERM 2

 

1(a)(i) A         –           Nucleus

C         –           Cell wall

 

(ii)       –    Maintain the shape of the cell;

  • Providing support to herbaceous plants; (any 1)
  • Stores sugar and salts;

 

(b)       Hypotonic solution / dilute solution / dilute sugar / salt solution.

 

(c)       The potato cell sap was lowly concentrated than the surrounding solution; hence lost

water molecules by osmosis (through semi-permeable membrane) to become plasmolysed.

 

(d)       –           Opening and closing of stomata.

–           Absorption of water by root hairs.

–           Absorption of water in intestines.

–           Reabsorption of water in kidney nephron.   (any 2)

–           Feeding in insectivorous plants.

–           Movement of water from cell to cell.

–           Osmoregulation.

 

2(a)     Cartepillars

  • Aphids

Mice                      each (1/2 mk)

Slugs

 

  • Primary consumers

 

(b)(i)   Plants              Cartepillars                 Insectivorous                          hawks ;

Birds

 

(ii)   Plants              Slugs                           Frogs               Snakes             Hawks           (any 1)

 

 

Plants              Aphids                        Beetles                        Insectivorous              Hawks

Plants

 

(c)(i)   Largest Biomass  –    plants

Directly obtain energy from the sun.

 

(ii)       Least biomass  –   Hawks

  • Loss of energy in form of heat, respiration, defaceation, excretion.

 

  • Sun / solar energy.

 

 

 

 

3(a)     A  –   Villus

B  –   Lacteal

 

(b)       A  –  Increases surface area for maximum digestion and absorption.

B  –  Absorption of fatty acids and glycerol.

 

(c)       –           Final digestion of food.

–           Absorption of soluble products of digestion.

 

(d)       Produces bile juice which contain bile salts that emulsify fats; and neutralizes the acidic chyme from the stomach;

 

4(a)     Deamination

 

(b)       Liver

 

(c)       –           Removal of excess amino acids.

–           Availing of energy in the body.                       (any 1)

–           Formation of glycogen / fats for storage.

(award any one)

(d)       Urea

 

(e)       It is transported to the kidney where it is excreted.

 

(f)        (i)        Diabetes inspidus

 

(ii)       Antidiuretic Hormone / Vasopressin

 

(iii)      Pituitary gland.

 

5(a)     To remove / expel dissolved air from the glucose solution.

 

(b)       To prevent entry of oxygen into the yeast – glucose solution.

 

(c)       Anaerobic respiration.

 

(d)       Becomes white precipitate.

 

(e)       High temperature kills the yeast cells; hence the reaction stops;

 

(f)        –           Making of beer / Brewing / Ethanol / Alcohol.

–           Baking industry / Raising of the dough.                        (any 2)

 

 

6(a)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  • Axes labelling (2mks)

Scale (x and y – axis)  (2mks)

Curve plotting  – each (1mk)  total 2mks

Curve labeling  –  each (1mk)  total 2mks

 

(b)(i)The population of locusts increase with increase in the amount of rainfall.

 

(ii)Increased amount of food;

Improved breeding conditions;

 

  • The population of both decreases;

Less food availability to locusts and crows.

 

  • Capture – Recapture method.

 

  • (i) Locust – Primary consumers

 

Crows – Secondary consumers

 

(ii)       Grass              Locusts               Crows

 

  • Grass would increase

crows would reduce

 

  • (i) Biomass – The total dry weight of organisms at a particular trophic level.

 

  • Ecosystem – A natural unit composed of abiotic and biotic factors whose

interactions lead to a self-sustaining system.

 

  1. Xerophytes
  • Have thick cuticle to prevent cuticular transpiration.
  • Have reduced stomata on lower leaf surface to lower transpiration.
  • Fold or curl leaves in dry weather to protect stomata from direct sunlight.
  • Have reversed stomatal opening rhythm where they open at night to reduce water loss.
  • Have succulent stems and leaves to store water for use in dry season.
  • Some have superficial roots to absorb light showers of rain.
  • Some are deep rooted to absorb water from water table.
  • Shedding of leaves during dry season.
  • Some have short life cycles and survive as underground perennating structures or seeds during drought.
  • Hairy leaves.
  • Sunken stomata 1 x 10 = 10mks.

 

Hydrophytes

  • Submerged plants have dissected leaves to increase surface area for maximum light absorption.
  • Emerged plants have broad leaves with stomata on upper surface to increase transpiration.
  • Have aerenchyma tissue to increase buoyancy and for gaseous exchange.
  • Floating water plants have raised flower for pollination.
  • Poorly developed roots that lack root hairs to reduce absorption of water.
  • Some submerged plants have sensitive chloroplasts that photosynthesise in low light intensities. 5 x 2 = 10mks

 

 

  1. High body temperature above normal:
  • Sweat glands; Produce sweat; water in the sweat evaporates / sweat evaporates; absorbing latent heat of vaporization producing a cooling effect;
  • Hairs lie flat; due to relaxation of erector pilli muscles; no / little air is trapped; hence increased heat loss from the body;
  • Blood vessels / arterioles; vasodilate / dilate; more blood flow to the skin hence loss of heat from the body, by radiation and convection;

When body temperature is low below normal:

  • Sweat glands produce less / no sweat; no latent heat is absorbed; more heat retained in the body;
  • The hairs stand upright / erect; to trap air between them; that insulate the body against heat loss; more heat retained in the body.
  • Blood vessels / arterioles vasoconstrict / constrict;

Less blood flow to the skin; reduces heat loss / more heat is retained in the body;

 

(20mks)

 

(;) means a marking point.

 

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