K.C.S.E Biology Q & A - MODEL 2014PP1QN10
What is meant by each of the following terms?
(i) Crenated cell.
(ii) Flaccid cell.
(i) Crenated cell is a shrunk animal cell that has lost water by osmosis;
(ii) Flaccid cell is a flabby /shrunk plant cell that has lost waster by osmosis;
K.C.S.E Biology Q & A - MODEL 2014PP1QN10
Explain two roles of diffusion in human beings.
K.C.S.E Biology Q & A - MODEL 2014PP1QN05
The diagram below shows a set up for an experiment to demonstrate a certain physiological process.
(a) What nature of solution is represented by 20% sugar solution?
(b) Explain the observation made on the set up after one hour.
K.C.S.E Biology Q & A - MODEL 2013PP1QN30
State two ways in which osmosis is significant to plants.
K.C.S.E Biology Q & A - MODEL 2013PP1QN05
Describe how turgor pressure builds up.
K.C.S.E Biology Q & A - MODEL 2013PP1QN01
Explain how an increase in temperature affects the rate of active transport.
K.C.S.E Biology Q & A - MODEL 2012PP2QN03
(a) In an investigation, equal amounts of water was placed in. three test-tubes labelled G, H and J. Pondweeds of equal length were dropped in each test tube. The test-tubes were then placed in identical conditions of light and carbon (IV) oxide at different temperatures for five minutes. After the five minutes, the bubbles produced in each test-tube were counted for one minute. The results were as shown in the table below.
(i) Name one requirement for this process that is not mentioned in the investigation.
(ii) Name the gas produced in this investigation.
(iii) Account for the results in test-tubes H and J.
(b) State two ways in which the human intestinal villus is adapted to its function.
(a) (i) chlorophyll;
(ii) oxygen; (1 mark)
(iii) Test tube H is at optimum temperature for enzyme activity; hence high rate of
photosynthesis/more bubbles. In test tube J most enzymes have been denaturedby the high temperature; hence low rate of photosynthesis/fewer bubbles.
(b) — The villus epithelium is thin; for faster diffusion of dissolved food substances;
— The epithelium has goblet cells; which produce mucus to lubricate food passage;
— They have microvilli; which further increase their surface area for absorption;
Have lacteal; for absorption of fatty acid & glycerol/transportation of lipids;
Highly vascularised; for absorption of digested food.
K.C.S.E Biology Q & A - MODEL 2012PP1QN16
The diagram below represents an experimental set-up used by students to investigate a certain process.
Flower Q produced seeds while P did not. Account for the results.
K.C.S.E Biology Q & A - MODEL 2012PP1QN13
State three factors that affect the rate of diffusion.
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
K.C.S.E Biology Q & A - MODEL 2012PP1QN07
The diagram below represents a set-up that students used in an investigation.
(a) Name the physiological process that was being investigated.
(b) State the role of potassium hydroxide in flask K.
(c) Account for the observation in boiling tube L and flask N.
(a) Respiration/aerobic respiration;
(b) Flask K Potassium hydroxide removes Carbon IV Oxide from atmospheric air;
(c) 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;
K.C.S.E Biology Q & A - MODEL 2012PP1QN04
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.
(a) Account for the results in the table above.
(b) What would be a suitable control set-up for the investigation?
(a) 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;
(b) Pawpaw cylinders of the same size/length; placed in an isotonic solution;
Boiled potato cylinders of the same size; placed in a similar solution;
K.C.S.E Biology Q & A - MODEL 2011PP2QN06
Explain how the osmotic pressure in the human blood is maintained at normal level.
K.C.S.E Biology Q & A - MODEL 2011PP1QN07
The diagrams below show an experimental set-up to investigate a certain process in a plant tissue.
Explain the results obtained after 30 minutes.
K.C.S.E Biology Q & A - MODEL 2010PP2QN06
In an experiment to investigate a certain physiological process, a boiling tube labelled A and a test tube labelled B were covered with cotton wool. The two tubes were simultaneously filled with hot water and fitted with thermometers. The experimental set-up was as in the diagrams below.
Temperature readings were taken at the start and after every two minutes for twenty minutes. The results were as shown in the table below.
(a) Using the same axes, draw graphs of temperature against time.
(b) (i) Work out the rate of heat loss in the boiling tube labelled A and test-tube labelled B between the 5th and 15th minutes.
(ii) Account for the answers in (b) (i) above.
(iii) How does the explanation in (b) (ii) above apply to an elephant and a rat?
(c) (i) State the role of the cotton wool in this experiment. ,
(ii) Name two structures in mammals that play the role stated in (c) (i) above.
(d) State three advantages of having constant body temperature in mammals.
(b) (i) A: 56—48.5 7.5C
7.5C/10 Minutes ; = 0.75C Per Minute; ±0.05
14C/10 Minutes ; =1.4C Per Minute; ±0.05
(ii) B has a larger surface area to volume ratio; making it to lose heat to the surrounding faster; (the converse is true)
(iii) A rat has larger surface area to volume ratio compared to an elephant; making the rat to lose heat at a faster rate than an elephant;
(c)(i) Insulation/insulate against heat loss; (to surrounding);
(ii) Subcutaneous fat layer / adipose tissue;
Fur / hair; .
(d) Are active always; (even under very cold conditions)
Are able to escape from predators/search for mates/food; (because they are active always)
Can survive in a wide variety of habitats: (both cold and hot)
K.C.S.E Biology Q & A - MODEL 2010PP1QN07
Distinguish between haemolysis and plasmolysis.