A group of students set up an experiment to investigate a certain physiological process. The set up
was as shown in the diagram below.
(a) What physiological process was being investigated? (1mk)
(b) (i) State two major observation that was made after some time. (2mks)
Distilled in the Irish potato would reduce in level; (1mk)
Level of concentrated salt solution would increase in the Petri dish(2mks)
(ii) Account for the above observation in b (i) above. (4mks)
Concentrated salt solution in the Petri-dish has higher osmotic pressure than the cells of the Irish potato; these cells lost water to the salt solution by osmosis; these cells become more concentrated and drew water from the neighbouring cells; this process continued until the cells in contact with water in the potato drew it up. (4mks)
(c) State the significance of the biological process involved in the experiment. (1mk)
The diagram below shows a specialized cell from a human being.
(a) Identify the cell. (1mk)
(b) Name the parts labelled A,B, and C. (3mks)
(c) State the functions of the part labeled D. (1mk)
Propels the sperm forward
(d) A student observed cells under a microscope and counted six (6) cells a cross the diameter of view. The diameter of field of view was found to be 1.25mm. Calculate the length of one of the cells observed. ( Answer in micrometer). (3mks)
A person accidentally touches a hot pan and responds as illustrated in the diagram below.
(a) Explain how the response illustrated above occurs. (b) Explain how auxins are utilised as selective weed killers in agriculture.
(a) The stimulus /heat/pain is detected by temperature/pain receptor( Thermo receptors) in the skin/dermis; An impulse is generated; impulse is transmitted along a sensory neurone to the CNS/spinal cord; (chemical) transmission across synapse to relay neurone; Across a synapse to motor neurone; across a synapse to biceps muscles,/effector via motor neurone; muscles/effectors contracts; (hand moves away). This is known as (simple reflex action);
In cats, the gene for fur colour is sex-linked. Letter G represents the gene for ginger fur colour while letter B represents the gene for black fur colour in a given cat species. These genes are co-dominant. Heterozygous females have ginger and black patches of fur and their phenotype is described as tortoise-shell.
(a) With reference to the information given above, what is meant by the term co-dominance? (b) Explain why male cats with a tortoise-shell phenotype do not usually occur. (c) A tortoise-shell female was crossed with a black male. Determine the genotypes and phenotypes of the offspring.
In an experiment, students treated seedlings as illustrated below.
(i) Account for the observations made in seedling I. (ii) Explain the similarity in the end results made in seedlings II and III. (iii) State the likely treatment that would make seedlings II and III respond like seedling I.
(i) Positive phototropism/tip bends towards light; light causes migration of auxins (produced at the tip) to the darker sides; (of the shoot) resulting in faster division of cells/ elongation/growth on the darker /opposite side of the shoot hence bending towards light
(ii) both seedlings remain upright; ( erect) seedling II does not have tip while seedling III the tip has been covered by opaque material preventing light causing unequal distribution of auxins; . uniform/even distribution of auxins)
(iii) Fitting a gar block treated with auxins at the decapitated end of seedling II; Removing the opaque material covering the tip of seedling III/ replacing the opaque cap with a transparent one;
The table below shows results of blood cell counts per mm3 of blood from a sample of people living at different altitudes.
(a) Explain the relationship between: (i) red blood cells count and the altitude; (ii) white blood cells count and the altitude. (b) Explain why chances of nose-bleeding increase with altitude in humans.
(a) i) Number of red blood cells increase with altitude; to increase oxygen carrying capacity (by haemoglobin molecules in blood); since oxygen concentration is lower at higher altitude;
ii) white blood cells serve to protect the body against harmful microorganisms/pathogens; thernadites of pathogen of the body to microbial attack is not dependent on the altitude (to be countered by the white blood cell); hence 6 the number of white blood cell count is constant at whatever altitude;
(b) Atmospheric Pressure decreases with the increase in altitude; the imbalance between the (outer) atmospheric pressure at high altitude and the internal blood pressure (generated by the heart) results in (one) nose bleeding at high altitudes/ internal blood pressure is higher than the (outer) atmospheric pressure.
In an experiment to investigate the effect of sodium chloride on the growth rate in a spinach seedling, seeds were treated with different concentrations of sodium chloride. The results are as recorded in the table below.
(a) From the results in the table above, explain the effect of increasing the concentration of sodium chloride. (b) Apart from a ruler, state two other equipment one would need to determine the rate of growth in the roots. (c) With a reason, state one other part of the seedling the students would focus on to determine the effect of sodium chloride on growth. (d) State the likely effect on the seedling of increasing the concentration of sodium chloride to 2.20mol/l
(a) Increased Nacl concentration/having more Nacl ions decreases water potential/decrease osmotic potential/ increase osmotic pressure/makes water potential more negative outside the seed/seedling in the surrounding solution to be hypertonic to the cell sap in the seedling ; seeds cells take in water by osmosis) are dehydrated/lose water molecules to the surrounding solution , reducing the growth enzyme activity; have reduced growth rates;
Pen; Marker (pen);
Dye/water proof ink/ bloating paper/tissue paper
(c) Rate of growth/ increase in length of shoot tip/apex
it is a region of (active) cell division/growth
(d) The seedling will be (dehydrated) /lose water (hence) wither/die/dry
The photograph below represents a plant in a Certain Division
(a) (i) Name the Division to which the plant belongs.
(ii) With reference to the Photograph, state three observable features of the Division named in a(i) above.
(b) Name the part labelled N and P.
(c) Explain how the part labelled Q is adapted to its function
a) i. Bryophyta; ii. Has capsules (for enclosing spores);
Has (long) setae (for supporting the capsules/for effective propagation of spores); (Developed) rhizoids (for anchorage/absorption of water/mineral salts);
Thalloid in nature/Thallus/undifferentiated; b) N — Capsule;
P—Seta; (c)Numerous/hair-like to increase the surface area for absorption;/to enhance rate of absorption of water/nutrients/dissolved mineral salts;
Numerous/hair-like to hold firmly on the surface/not to be easily blown away/displaced/anchorage;
The diagram below illustrates the arrangement of bones in a human arm.
(i) the type of joints formed at points H and M.
(ii) bone G
(b) Name bone J and state how it is adapted to its functions.
(c) State one functional difference between a tendon and a ligament.
a) i. H-Ball and socket (joint);
M - Gliding/planar/plane ii. Clavicle; b) Scapula;
Has a spine to increase surface area for muscle attachment;
It is broad/flat to increase the surface area for muscle attachment;
Forms flexible attachment above the ribs that allows movement of the arms;
Has a glenoid cavity/depression for articulation with the humerus/forming the ball and socket joint;
Has acromion for articulation with clavicle/for muscle attachment;
Has coracoid process to increase surface area for muscle attachment; c) Ligaments hold the bones together (at a joint) while tendons attach muscles to bones;
The amount of blood flowing tough certain pans in the mammalian body at different activity levels was measured and results tabulated as Shows in the table below.
(a) Account for:
(i) the high blood flow through the cardiac and skeletal muscles during strenuous exercises.
(ii) the results obtained for the alimentary canal at rest.
(b)Name two waste materials excreted by both the skin and the kidneys.
Below is a graphical representation of students’ height in a classroom.
(a) Name the type of curve illustrated.
(b) (i) State the type of variation represented by the curve.
(ii) State two meiotic processes that lead to variation among organisms.
(iii) Explain the role of variation in organisms.
(c) Explain the need for genetic counselling in present day health facilities.
a) Normal distribution curve;
b) i. Continuous (variation);
ii. Independent assortment;
iii. Organisms/individuals with advantageous traits/variations are favoured/selected by nature; and survive to reproduce/pass on/propagate the advantageous/favourable traits to their off-spring; Or
Variation ensures propagation of desirable/favourable traits; to the future generations/off-spring, ensuring improved/quality population; c) Provides information/advice to individuals/families/communities about genetic disorders;
Helps identify/test/advice families/communities on possible risks of genetic disorders;
Provides supportive services/serves as patient advocates/refer individuals/families to relevant health professionals;
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