KCSE 2012 Biology Paper 1 with Marking Scheme

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KCSE 2012 Biology Paper 2 with Marking Scheme

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How does nutrition as a characteristic of living organisms differ in plants and animals? (2 marks)
The diagram below represents a certain organism collected by a student at the sea shore.
1. Name the class to which the organism belongs. (1 mark)
2. Give three reasons for your answer in (a) above. (3 marks)
The figure below is a fine structure of a generalized animal cell as seen under an electron microscope.
1. Name the parts labeled A and B. (2 marks)
2. How is the structure labeled B adapted to its function? (2 marks)
In an investigation, a student extracted three pieces of paw paw cylinders using a cork borer. The cylinders were cut back to 50 mm length and placed in a beaker containing a solution.
The results after 40 minutes were as shown in the table below.

Feature Result

Average length of cylinders (mm) 56mm

Stiffness of cylinders stiff
1. Account for the results in the table above. (3 marks)
2. What would be a suitable control set-up for the investigation? (2 marks)

The table below shows results of a study of three plants C, D and E growing in different habitats.

Feature	Plant C	Plant D	Plant E
Number of stomata on upper surface of leaf per square area	4	20	6
Number of stomata on lower surface of leaf per square area	6	0	8
Thickness of leaf cuticle (mm)	0.4	0.1	0.2
Surface area of roots (cm²)	2000	1000	1200

Which one of the plants C, D and E grows in the area of relatively low water availability? (1 mark)
Explain your answer in (a) above. (3 marks)

The diagram below represents part of the gaseous exchange system in human.
1. Name the parts labelled F and G. (2 marks)
2. State one function of each of the parts labeled H and J. (2 marks)
The diagram below represents a set-up that students used in an investigation.
1. Name the physiological process being investigated. (1 mark)
2. State the role of potassium hydroxide in flask K. (1 mark)
3. Account for the observation in boiling tube L and flask N. (2 marks)
What is the probability of a couple with blood group AB getting a child with blood group AB? (4 marks)
State the importance of negative phototaxis in termites. (1 mark)
What is meant by the term irritability? (1 mark)
1. State two ways in which the heart muscles are special. (2 marks)
2. Name the muscles found in the following organs: (2 marks)
1. Name the part of a light microscope used to bring an image of a specimen into sharp focus. (1 mark)
2. Why is it recommended to keep the stage of the microscope dry? (1 mark)
State three factors that affect the rate of diffusion. (3 marks)
1. Name the type of respiration that is most effecient. (1 mark)
2. Give a reason for your answer in (a) above. (1 mark)
What name is given to a group of hormones that control the development of secondary sexual characteristics in a human male? (1 mark)
The diagram below represents an experiment set-up by students to investigate a certain process.

Flower Q produced seeds while P did not. Account for the results. (3 marks)
Name two substance that leave the foetal blood through the placenta. (2 marks)
Why are plants able to accumulate most of the waste products for long? (1 mark)
List four symptoms of diabetes mellitus. (4 marks)
State three aspects that can be used to estimate growth in seedlings. (3 marks)
Name the process through which free atmospheric nitrogen is converted into nitrates. (1 mark)
State the importance of divergent evolution to organisms. (2 marks)
Name the strengthening materials found in the following support tissues: (2 marks)
1. collenchyma; ................................................................................................
2. xylem. .........................................................................................................
State four characteristics of apical meristem cells. (4 marks)
State the role of the following hormones in the life cycle of insects: (2 marks)
ecdysone hormone; .......................................................................................
juvenile hormone. ..........................................................................................
1. State the theories of evolution proposed by the following scientists. (2 marks)
  Charles Darwin .............................................................................................
  Jean-Baptiste de Lamarck. ..............................................................................
2. State the evidence of the evolution based on (2 marks)
  1. cell organelles .......................................................................................
  2. fossils ...................................................................................................
What is the function of contractile vacuoles in amoeba? (1 mark)
State two differences between open and closed circulatory systems. (2 marks)
Name two nutrients that are absorbed without being digested by enzymes in humans. (2 marks)
Name the organelle that is involved in each of the following: (2 marks)
1. manufacture of lipids; ........................................................................................
2. formation of lysosomes........................................................................................

MARKING SCHEME

Plants make their own food from Carbon (IV) Oxide and water in the presence of light autotrophic/ photosynthesis; while animals eat ready made food from plants or animals/heterotrophic nutrition;
(2 marks)
1. Crustaceae/crustacea; (1 mark)
2. - Head fused with thorax/has a cephalothorax;
  - Have two pairs of antennae;
  - Have compound eyes/a pair of compound eyes;
  - Have several pairs of limbs/five to twenty pairs of limbs;
  - Exoskeleton is hard;
  - Have external gills;
  - Four pairs of mouth parts consisting of maxilla, maudiblis, labium and labrum.
    (max 3 marks)
1. 1. A-nucleopore;
  2. B-Rough Endoplastic Reticulum;
    (2 marks)
2. Surface covered with ribosomes; for protein synthesis; Has interconnected channels: for transportation of proteins; (2 marks)
1. The solution was hypotonic/less concentrated compared to the cell sap of pawpaw cylinder cells; The tissue/cells gained water by osmosis; becoming turgid/longer/stiff, (3 marks)
2. Pawpaw cylinders of the same size/length; placed in an isotonic solution; Boiled potato cylinders of the same size; placed in a similar solution;
  (2 marks)
1. Plant C; (1 mark)
2. - Thick cuticle reduces water loss;
  - Low number of stomata reduces water loss;
  - Large root-surface area enhances water absorption;
    (3 marks)
1. F- Bronchiole;
  G - Intercostal muscles/external intercostal muscles;
  (2 marks)
2. H - (Pleural membranes) secretes encloses pleural fluid to lubricate lungs/protect lungs: (1 mark)
  J - (Diaphragm) separates chest cavity from abdominal cavity/works to effect volume and pressure changes in chest cavity necessary for inhalation and exhalation/ ventilation/breathing; (1 mark)
1. Respiration/aerobic respiration; (1 mark)
2. Flask K Potassium hydroxide removes Carbon IV Oxide from atmospheric air; (1 mark)
3. L-Lime water remains clear because Carbon (IV) Oxide has been removed;
  Flask N lime water forms a white precipitate because the respiring cockroaches produce Carbon (IV) Ovide; (2 marks)
Parental genotype is AB

Probability is ½ or 0.5/50%; (4 marks)
Reduces dehydration; Avoid predators; (max) (1 mark)
Ability of an organism to detect, interpret and respond to changes in the environment/stimulus;
(1 mark)
1. Can contract continuously without fatigue; Their contraction is started by the muscles themselves/myogenic; (2 marks)
2. stomach: smooth;
  bone: skeletal; (2 marks)
1. Fine adjustment knob; (1 mark)
2. Avoid refraction of light;
  Prevent wetting of the slide; (1 mark) (max)
Temperature; surface area; distance that particles have to travel; diffusion/concentration gradient; size/density of particles, surface area to volume ratio; thickness of membrane: medium of diffusion
(3 marks)
1. Aerobic respiration; (1mark)
2. It releases more energy per unit mass; (1 mark)
Androgens; (1 mark)
The plant/flower is self sterile/not successfully self pollinated; covering prevents pollination; in flower P. Flower Q received pollen from other plants/cross pollination; (3 marks)
Carbon IV Oxide;
Nitrogenous waste/urea; (2 marks)
Most of the waste products are harmless; Converted into harmless products; (1 mark)
Passing urine frequently/polyuria; glucose/excess glucose in blood/hyperglycaemia; constant feeling of thirst/dehydration; loss of weight; excessive eating/increased appetite/polyphagia/ hyperphagia; poor resistance to diseases; (4 marks)
height/length; weight/mass; surface area; (3 marks)
Nitrogen fixation; (1 mark)
Results in adaptations that enable organisms to exploit different ecological niches, leads to the formation of new species; (2 marks)
1. Cellulose;
2. Lignin;
  (2 marks)
Small/round; central nucleus/prominent nucleus; dense cytoplasm/protoplasm, no vacuoles; continuously dividing; thin cell walls (4 marks)
Ecdysone causes metamorphosis; towards adult stage
Juvenile hormone maintains larval characteristics; (2 marks)
1. Theory of natural selection; (1 mark)
  Theory of environmental influence on inherited characteristics; (1 mark)
2. 1. Similar organelles performing similar functions in different organisms suggest a common ancestry/cell biology; (1 mark)
  2. Fossil records/palaeontology/by comparing fossils to show phyllogenetic relationship between organisms/common ancestry: (1 mark)
Removes excess water/waste products/Homeostasis; (1 mark)

Open	Closed
Blood flows in haemocoel/ sinuses/body cavity directly in contact with cells	Blood confined in vessels;
Blood flows at low pressure	Blood flows at high pressure;
Blood lack pigments	Blood has pigments for oxygen and Carbon (IV) Oxide transportation

(2 marks)