INSTRUCTIONS TO CANDIDATES
- This paper consists of sections A and B answer all questions in section A
- In section B answer question 6 compulsory and either question 7 or 8
- Answer all the questions
- The figure below represents a set up that was used to investigate a certain process in a plant.
- State the aim of the experiment. (1mk)
- Why was sodium hydrogen carbonate added to water in this experiment? (1mk)
- Explain why the number of bubbles reduced by evening. (2mks)
- Explain the use of the following in this experiment
- Water plant (2mks)
- Wooden block (1mk)
- Write a word equation to represent the chemical process being investigated. (1mk)
- The figure below represents a diagram of a potometer
- What is the potometer used for ? (1mk)
- State the precautions which should be taken when setting up a potometer (3mks)
- Explain what you will expect if set up was placed under the following environmental conditions;
- Dark room (2mks)
- Leafy shoot enclosed in polythene bag (1mk)
- In a current of air created by a fan (1mk)
- In an experiment to investigate on aspect of digestion, two test tubes A and B were set-up as shown in the diagram below;
The test tubes were left in the bath for 30minutes.The content of each test tube was then tested for starch using iodine solution:-- What was the aim of the experiment? (1mk)
- What results were expected in test-tube A and B (2mks)
A
B - Account of the results you have given in (b) above in test tube A and B
Test tube A (2mks)
Test tube B (2mks) - Describe the procedure of testing for starch (1mk)
- The diagram below represents a part of thoracic region of a human being;
- Name the structures labeled K and L (2mks)
K
L - How does structure R bring about inhalation (4mks)
- Give the scientific name of the organism that causes whooping cough (1mk)
- Name the main site of gaseous exchange in human being. (1mk)
- Name the structures labeled K and L (2mks)
- The diagram below shows the vertical section of a female reproductive system
- Name the parts labeled A and B (2mks)
A
B - Name the gonadotrophic hormone that affects the part labeled A (1mk)
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- State a hormone(s) produced by each of the following structures in a female: (2mks)
Ovary
Placenta - State one effect of each of the above hormones on uterine wall (2mks)
- State a hormone(s) produced by each of the following structures in a female: (2mks)
- Name a sub-division in the kingdom plantae that exhibit double fertilization (1mk)
SECTION B (40 MKS)
Answer question 6 (Compulsory) and either question 7 or 8 in the spaces provide after question 8
- Name the parts labeled A and B (2mks)
- The table below shows the changes observed in the dry weight (in milligrams) of a barley seedling, its embryo and endosperm during the first ten days after the onset of germination.
DRY WEIGHT IN MILLIGRAMS TIME (DAYS) EMBRYO ENDOSPERM WHOLE SEEDLING 0 2 41 45 2 2 39 43 4 7 32 41 6 15 21 38 8 22 11 35 10 35 6 43 - Using a suitable scales on the same axis, plot graphs of dry weight of embryo endosperm and whole seedling against time. (8mks)
- State and account for the changes in dry weight shown by:
- Embryo (4mks)
- Endosperm (4 marks)
- Explain the role of water during germination. (4 marks)
- Using a suitable scales on the same axis, plot graphs of dry weight of embryo endosperm and whole seedling against time. (8mks)
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- Describe the process of fertilization in a flowering plant. (15mks)
- State the changes that take place in a flower after fertilization. (5mks)
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- Describe the dentition of carnivorous mammals and their adaptation to the mode of feeding. (10mks)
- Activities of humans are contributing to the pollution of water bodies. Describe the causes and methods of controlling water pollution in Kenya. (10marks)
MARKING SCHEME
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- The aim of the experiment is to test the plant for photosynthesis.
- Adds carbon (IV) oxide to the water;
- At evening the light intensity has reduced; hence reduction in the rate of photosynthesis;
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- Water plants are able to extract dissolved carbon(IV)oxide in water;
- Water plants are able to use low light intensity under water;
- Facilitate air circulation/ movement in water;
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- Measure rate of transpiration;
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- Assemble apparatus under water;
- Apply vasectomy between cork shoot contacts;
- Open the reservoir tap;
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- The air bubble will not move, no photosynthesis in absence of light/ dark place;
- Water droplets will be seen in the polythene because of trapped and condensed water vapour;
- Air bubble will move faster due to increased rate of transpiration. Air current drive away water moisture around the leaves of plants and increase the saturation deficit
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- To investigate the effect of boiled saliva on starch/to show the effect boiled/denatured enzyme amylase has on starch;
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- A - brown colour/ colour of iodine persists;
- B - blue black/ blue colouration;
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- A - starch has been digested/ starch has been broken down/ amylase hydrolyses starch; hence no colour changes;
- B - enzymes/amylase denatured; hence no starch digested;
- Put the 2cm3 of food substance into a test tube add 2/3/4 drops of iodine solution;
- Note: a known volume mentioned eg Rj if the volume is presented as 2cm. A definite number of drops mentioned Rj. A range eg 2-3 drops
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- K - pleural membrane ;
- L – intercostal muscles; acc external and internal muscles
rej intercostal muscle 2mks
- R (diaphragm) muscles contract; causing it lie flat / flatten; This increases volume of the thoracic cavity / lungs; (hence lowering the pressure inside) and air is forced in; 4mks
- Bordetella pertussis scientific rules to be followed 1mk
- Alveolus/ alveoli 1mk
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- A...........ovary
- B...........cervix acc uterine wall 2mks
- FSH (Follicle Stimulating Hormone) rej F.S . H 1 mk
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- Ovary --- oestrogen / progesterone
- Placenta – progesterone 2 mks
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- Oestrogen – causes repair and healing of endometrium 1mk
- Progesterone-----
- causes thickening of endometrium
- Causes increased blood flow any 1 = 1mk
- (vascularisation ) to the endometrium
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- Angiospermaphyta
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- The weight of the embryo is steadily increasing; cells of the embryo undergo mitotic cell division; and synthesis new protoplasm; hence the increase in weight;
- 1st to 2nd days, the dry weight remains the same; because the enzymes breaking down the food reserve in the endosperm are being activated;
- From 3rd day up to the end of the dry weight increases; because the products of hydrolysis in the endosperm are translocated to the embryo, and used in synthesis of new cellular components;
- Decrease in weight; stored food is hydrolysed; and transported to growing regions; for respirations and synthesis of new
- 1st and 2nd days, dry weight decreases gradually; due to the hydrolysis of food reserve in the endosperm;
- From the 3rd day, dry weight decreases rapidly until the decreases rapidly until the 8th day after which the decrease is slow; due to further hydrolysis of food reserve, the products are translocated to the embryo during germination; cellular materials;
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- Hydrolysis of stored food;
- Activation of enzymes and germination hormones;
- Medium for chemical reactions;
- Medium for transport for hydrolysed nutrients to growing regions.
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- Pollen grains a stick in the stigma surface; that surface of stigma produces a chemical substance ; which stimulates the pollen grain to produce a pollen tube/germinate. The pollen tube grows down ( into the tissue of the style) from where it derives nutrient; the generative nucleus divides to give rise to two male nuclei and the embryo sac contains eight nuclei, 2 synergids, ovum two polar nuclei, and three antipodal cells, when pollen tube reaches the micropyle the vegetative nucleus/ pollen tube nucleus in the pollen tube disintegrates and male nucleus fuses with the egg cell and form the triploid nucleus/ zygote.
- The other male nucleus fuse with the two polar nuclei to form a triploid nucleus/ primary endosperm.
- The process involves double fertilization.
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- Intergument changes into seed coat/ testa
- Zygote into embryo
- Ovary wall into pericarp
- Ovary into fruit
- Petals dry and fall off
- Intergument and embroyonic mother cell form the seed
- Flower stalk into fruit stalk
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- Have sharp pointed incisors ; for tearing and stripping flesh from bones
- Have canines that are long / curved / pointed; for piercing , grasping and holding the prey;
- Have got the carnassial teeth (upper fourth premolar and lower first molar) with smooth sides; sharp edges to shear and slice flesh from tendons and crush the bones;.
- Have powerful jaw bones for powerful muscle attached; This prevents dislocation of jaws for cutting and shearing of flesh;
- Have sharp and curved claws; for holding and grasping prey; ( 10mks)
- Causes of pollution/water pollutants.
- Domestic effluents/garbage/animal bones/broken glasses/plastics/polythene;
- Human waste/sewage;
- Phosphate detergents;
- Industrial wastes e.g heavy metals such as lead/copper/mercury/chromium;
- Hot water;
- Oil spillage;
- Agro chemicals ;eg inorganic fertilizers;
- Herbicides/insecticides/fungicides/pesticides;
- Silting/soil erosion;
Methods of control: - Treating domestic water; utilizing human waste in biogas production;
- Using biotechnology;
- Recycling of plastic/glass/polythene;
- Banning the use of phosphate detergents;
- Treating industrial effluents /cooling hot water before discharging;
- Establishing industries away from water bodies;
- Cleaning spilt oil using biotechnology/bacteria eg pseudomonas;
- Penalizing the companies/industries/individuals that cause oil spills/water pollution;
- Use mechanical/biological methods to control pests/weeds;
- Use biodegradable/manure/organic fertilizers/pesticides.;
- Use appropriate farming methods/contour farming/re aforestation/building of gabions/terracing/avoid farming on steep grounds; Total : max 10mk
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