BIOLOGY PAST PAPERS.
[QUESTION AND ANSWERS]
[QUESTION AND ANSWERS]
Movement of molecules against concentration gradient; using energy
2. What is meant by the terms
(i) Hypogynous flower
Conditions where other floral parts are positioned/ arise below the ovary/superior ovary
(ii) Pistillate flower
female flower,
3. Distinguish between analogous and homologous structures.
Analogous- structure which (appear similar and) perform similar / same functions but different origins;
Homologous - structure which have a common origin but (have evolved) to perform different function;
4. (a) State the function of co-factors in cell metabolism.
(b) Give one example of a metallic co-factor.
iron /mg/zn/cu/ca/Mn4/cobalt/molybdenum/k
Fe 2+ Mg 2+ Zn2+ Cu 2+ Ca2+ Mn Acc Correct Ionic Form;
5. Suggest three measures that can be taken to control infection of man by protozoan parasites.
Proper disposal of human waste/feaces;
Destroy breeding sites of vectors
Proper cooking of food /boiling of drinking water;
Use of insecticide against vectors / drugs against pathogens
Use of protective dwelling /mosquito nets to prevent vector bites/ proper hygiene;
6.Explain what would happen to onion epidermal cells if they were placed in distilled water. cell sap is more conc. Than the surrounding water, water get into the cell by osmosis;
the cell swell/become turgid; but doesn’t burst due to the cell wall,
7. State the characteristics that can separate the following organisms into respective classes – millipedes, Tsetse fly and spider.
body parts/division
number of limbs /legs;
body segments
8. Which type of a joint is found at the articulation of
a) Pelvic girdle and femur.
1. Ball and socket;
b) Humerous and ulna
Hinge
9. Name the blood vessel that transports blood from
(i) heart to the lungs.
Pulmonary artery;
(ii) Small intestine to the liver
Hepatic portal vein;
10. State three ways that the tracheole system in insect is adapted for gaseous exchange.
Large surface area;
Thin membrane
Moist surface
11. a) State the role of light in the process of photosynthesis.
To split water/photolysis;
b) Name one of the end products of dark reaction in photosynthesis.
Glucose
12. State the role of the following hormones in the human body.
a) Insulin
Regulation of blood sugar/ control conversion of glucose to glycogen
b) Antidiuretic hormone
control re-absorption of water in the kidneys/ nephron/ loop of Henle /regulation of water in the body osmotic pressure of the blood;
13. a) What happens to excess fatty acids and glycerol in the body?
converted to fat; and stored; (beneath the skin, or around body organs)
b) State two functions of muscles found in the alimentary canal of mammals.
peristalsis
Acts as a valve;
14. a) Name the tissue that is responsible for secondary thickening in plants.
Secondary cambium /cork cambium/ vascular cambium;
c) What is the role of water in a germinating seed?
soften stored food for breakdown; soft seed coat;
Transport dissolved substances;
Medium of enzymes action;
15. a) State two functions of synovial fluid in a joint in a mammalian skeleton
Reduction of friction/lubrication; absorption of shock / distribution of pressure (at joint);
b) Name the three types of muscles found in a mammal.
Smooth muscle /visceral muscles;
Skeletal/ striated muscles;
Cardiac muscles;
16. What is the function of the following cells in the retina of the human eye?
Cones ------Discrimination of colour/details/accurate vision/colour perception/ sensitive to light of high intensity
b) Rods -----. Sensitive to light of low intensity/ dim light vision;
17. Name three types of chromosomal mutations.
Inversion; duplication; deletion; translocation; non-disjunction
18. The graph below shows the effects of sewage on the population of a species of bacteria in a certain river.
Account for the changes in population of bacteria between 2 and 10 Kilometres down the river. 2-5 km population increase – because sewage provide nutrients
5-10 km population decrease because of depletion of nutrients; in sewage/ decomposition of sewage is complete;
19. Explain how tendrils of climbing plants coil around a support
In coming into contact with the support Auxin concentration reduce on the side experiencing touch stimulus; reducing growth rate; making the plant bend round the support;
20. Name the spore producing structures in
a) Bryophytes.
Capsule;
b) Pteridophytes
Sori/ sorus
21. a) During which phase of meiosis does crossing over occur.
Prophase I
b) How do identical and fraternal twins arise?
(i) Identical twins
An ovum is fertilized; and later cells separate in the early cell division
(ii) Fraternal twins
Two ova are released; and fertilized by two different sperms;
22. a) Account for the loss in dry weight of cotyledons in a germinating bean seed.
stored food is used up/broken down by enzymes to provide nutrients for germinating embryo
b) State three effects of gibberellins on shoots of plants.
Promotes cell division/cell elongation; parthenocapy.
Formation of side branches of stems;
Affect leaf expansion and shape /retard leaf abscission
23. Which one of the cell organelles would be more numerous in,
a) An enzyme secreting cell.
Rough/ smooth – endoplasmic/ golgi bodies/ ribosome’s/ lysosomes
b) A rapidly respiring cell in comparison to other cells in the same organism?
mitochondria/ mitochondrion
24. The figure below represents a transverse section of a young root.
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a) Identify parts labelled A and B.
A - Root hair;
B - endodermis
b) State the function of the parts labelled A, C and D.
A- Absorption of water;
C- Transport water, transport mineral salt;
D- transport manufactured food;
25. Give reasons for each of the following;
a) Constant body temperature maintained in mammals.
Most enzymes in the body function within a narrow range of temperature;
High temperature denature enzymes
Low temperature. Inactivate enzymes inhibits enzymes;
c) Low blood sugar level is harmful to the body.
Sugar is a raw material for respiration; therefore less sugar leads to low rate of respiration; hence less energy available to the body / low rate of metabolism;
26. State two ways by which leaves of plants are adapted to gaseous exchange.
Broad/flat lamina; to provide large surface area for absorption of gases;
Thinness to allow gases to pass through a short distance; presence of stomata to ensure efficient diffusion of gases presence of air spaces for gases to diffuse easily/
27. Other than Energy,, name the other products of anaerobic respiration in plants.
carbon iv oxide;
ethanol / alcohol
BIOLOGY PAPER 2 [QUESTIONS AND ANSWERS]
SECTION A
1. During ecological study, students collected and marked 120 ants and released them. After 48 hours, the students captured another 90 ants, 20 of which had been marked previously.
(a) How many ants were there in the compound? Show your working.
Approximate population= No. of organisms in first catch X No. of organisms in second catch
No. of marked organisms recaptured
i.e. P= FM X SC
MR
= 120x90=540 ants
20
(b) What are the limitations of this method in sampling animal populations?
Does not consider migration of organisms into and out of study area;
- Does not consider the effect of paint used in marking on the animal’s behaviour;
- Released animals may not mix freely with the remaining population;
- Marked organisms may not have adequate time to mix with the rest;
- Does not consider the effect of weather on the organisms behaviour;
(c ) State 2 other methods which could be used to determine the population.
- Quadrant method
-Belt transect method
-Line transect method
2. a) Smokers are always at a high risk of suffering from respiratory infections. Explain.
Cigarette smoke inhibits action of cilia in respiratory tract;
This results in the accumulation of dust particles, micro- organism and mucus;
Bacteria invade cells of mucus membrane causing various respiratory diseases
b) The gills of fish and the skin of the frog are efficient in the exchange of gases. Which characteristics do they have in common?
- Large surface area for efficient diffusion of respiratory gases;
- Moistened all the time for respiratory gases to dissolve;
- Well supplied with numerous blood capillaries;
- Thin membranes for rapid diffusion of gases;
- presence of a ventilation mechanism ; Any 4@ 1 mk each
c) Which structures are used for gaseous exchange in plants found in marine water.
Breathing roots/ pneumatophores;
3. The figure below is a pedigree diagram showing the inheritance of phenylketonuria a disease transmitted through a recessive gene.
a) Using the symbols P for the normal gene and p for the phenylketonuric gene, write down the genotypes of the parents 1 and 2.
Both PP;
Explanation--- Both parents are phenotypically normal but produced a phenylketonuric child. This means that both must be heterozygous for the phenylketonuria gene
b) Work out the possible genotypes of the normal child 4.
Parental phenotypes normal X normal ;
c) Marriage between closely related individuals is always not advised in many communities. Give the biological explanation for this.
Marriage between closely related individuals leads to unmasking of harmful mutations; that were hidden in the heterozygous state;
4. Study the diagram below and answer the questions that follow.
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a) Which part(s) marked a-d, when defective after implantation may lead to abortion. Give a reason for your answer.
C; it is the uterine wall where implantation occurs;
b) The part labelled b can be removed after 4 months of pregnancy without interfering with the pregnancy. Explain.
Part b secretes the hormones oestrogen and progesterone before 4 months of pregnancy;
. This role is taken over by the placenta hence they have no active role; Progesterone and oestrogen maintain pregnancy
c) Under each of the following, state the name of the causative organisms.
i) Syphilis ------ Treponema pallidum;
ii) Candidiasis----- Candida albicans;
iii) Gonorrhea ----- Neisseria gonorrhea;
iv) AIDS ------- human immuno deficiency virus Rej. HIV
d) State 2 disadvantages of external fertilization.
e) Water;
- Replaces water lost in urine, sweat, faeces, expiration; in order to maintain a constant volume of body fluids;
- Water required for elimination of waste products from the body;
5. a) Define the following terms.
i) Ingestion.-- Ingestion refers to the process by which food materials are taken into the animals
body through the mouth;
ii) Egestion---- Egestion refers to the elimination of undigested and indigestible waste food materials from an organisms body
b) The breakdown of starch stops shortly after food enters the stomach. Explain
Hydrochloric acid - kills salivary amylase stopping its action on starch;
C] Give 2 non-nutrient components of a balanced diet and state the importance of each.
i) Water;
- Replaces water lost in urine, sweat, faeces, expiration; in order to maintain a constant volume of body fluids;
- Water required for elimination of waste products from the body;
{ii} Roughage;
- Stimulates peristalsis necessary for the movement of indigestible and undigested food towards the rectum;
Provides bulk to intestinal contents hence preventing constipation
d) Highlight 2 functions of hydrochloric acid contained in gastric juice.
- kills bacteria present in food ; provides a suitable PH for enzyme pepsin;
activates pepsinogen to pepsin
-Unfold proteins to enable pepsin to act on them;
SECTION B
6. Carbohydrates used during respiration and those formed during photosynthesis by a certain plant was measured over a period of 24 hours at an interval of 3 hours
Time of day
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12AM
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3AM
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6AM
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9AM
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12PM
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3PM
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6PM
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9PM
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11PM
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carbohydrates formed during photosynthesis (mg)
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0
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0
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5
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30
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60
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30
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5
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0
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0
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Carbohydrates used during respiration (mg)
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10
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10
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10
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10
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10
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10
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10
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10
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10
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Using the same axes,
(a) plot a graph of carbohydrate formed during photosynthesis and carbohydrate used during respiration against time.
Hints
Title- 1MK
Labelled axes 1MK
Correctly used scale 2MKS
Plotting of points. Any 3 correctly plotted points in each case 1 mk each
Labeling of curves 1 mk each
b) Calculate the net carbohydrate formed by the plant .
Carbohydrates formed during photosynthesis
0+0+5+30+60+30+5+0+0=130 mg;
Carbohydrates used during respiration
10+10+10+10+10+10+10+1010=90 mg;
Net carbohydrates formed=
Total carbohydrates formed – total carbohydrates broken down;
130-90=40 mg ;
OR
TITLE CARBONHYDRATES FORMED DURING PHOTOSYNTHESIS AND CARBONHYDRATES USED DURING RESPIRATION MEASURED OVER A PERIOD OF 24 HOURS SCALE.
x – axis 1 cm rep . 1 ½ hours ( 90 minutes)
y – axis
1 cm represents 5 mg of carbonhydrates
c) At what time of the day do the light compensation points occur?
6:36 Am ± 10 minutes ;
5:24 P.m± 10 minutes
d) Account for the shape of graph on carbohydrates.
(i) Between 12.00a.m and 3a.m
No carbohydrates; 1mk formed due to lack of sunlight;
(ii) Between 3.00a.m to 12.00noon.
Gradual increase in carbohydrates formed; 1mk due to increasing light intensity;
e) How could foggy weather influence the net amount of carbohydrates formed over the 24 hour period?
Reduced light available; hence carbohydrates formed becomes low
f) Give other external factors apart from temperature and light intensity that influence the rate of photosynthesis.
carbon (IV) oxide;
Moisture/ water
g) In which form are carbohydrates stored in
(i) Plant bodies.
Starch
(ii) Fungi.
Glycogen;
f) (a) What is homeostatis?
Homeostatis refers to the control and maintenance of a constant internal environment
around cells in the body irrespective of fluctuations in the external environment;
b) Discuss the homeostatic functions of the mammalian liver.
Regulation of blood sugar level;
Excess glucose is converted to glycogen ;and stored in the liver under the influence of the hormone insulin secreted by the pancreas. Another hormone called glucagon; stimulates the conversion of glycogen to glucose; when there is shortage of glucose in the body; Glucagon is also secreted by the pancreas
- Deamination;
The liver breaks down excess amino acids; The amino group is removed as ammonia; and the remaining carbon skeleton oxidized to carbon IV oxide and water; This process leads to release of energy. The carbon skeleton may be converted to glucose to be used during respiration;
- Detoxification;
Ammonia from the process of deamination is converted in the liver into urea; which is less toxic. Bacterial toxins are converted to less toxic substances by liver cells;
- Regulation of plasma proteins;
The liver produces most of the proteins found in blood; fibrinogen and prothrombin which play a role in blood clotting. Albumin and globunis are also produced by the liver. Globulins act as antibodies;. Albumin contributes to the maintenance of osmotic pressure in the body; Non essential amino acids are synthesized by the liver;
- Storage of vitamins A, B,D,E and K and mineral salts;
The liver store vitamins A, B, D, E and K. Iron released from the breakdownof erythrocytes is stored in the liver cells; in the form of a compound called ferritin. The liver therefore is a good source of these vitamins and iron;
- Heat production;
The various metabolic activities of the liver lead to release of heat energy; This energy is distributed by the blood to other parts of the body hence contributing to maintenance of constant body temperature;
- Inactivation of hormones and drugs;
After performing their functions, hormones and drugs are chemically modified to inactive compounds; The by-products are eliminated through the kidneys and faeces and via bile;
- Storage of blood;
The large size and high capacity for contraction and expansion of its veins enables the liver to hold a large volume of blood; It therefore regulates the volume of blood in the general circulation depending on the body’s requirements ;
- Regulation of fat metabolism;
When carbohydrates are in short supply in the body, fats in different parts of the body are mobilized and taken to the liver; The fats are oxidized to carbon (IV) oxide and water with the production of energy or modified and sent to tissues for oxidation;
Any 1 point with explanation 2mks
8. Discuss the adaptations seeds and fruits to dispersal.
Animal dispersal
Presence of hooks on ovary walls/ calyx e.g. in Bidens pilosa; for attachment on animals hair/ fur or clothes of human beings;
Succulent fruits; brightly coloured and scented fruits that attract animals; Some fruits are eaten together with seeds. The seeds have coats which are resistant to digestive enzyme; hence pass through the gut undigested and passed out through faeces far from the parent plant; e.g. passion, tomato, guava, lantana
- Water dispersal
Fruits and seeds dispersed by water are light; hence float on water. Their seed coats are waterproof; This avoids soaking;
In some fruits e.g. coconut, mesocarp is fibrous and spongy; Air is trapped making the fruit light.
Some water plants e.g. the waterlilly have seeds whose coats trap out bubbles. The bubbles make the seeds float on water; and can be carried away from the parent plant. The pericarp and the testa are waterproof; hence seeds remain afloat without soaking and sinking;
- Wind dispersal
Fruits and seeds should be light; and small; to be carried away by air currents.
Some fruits and seeds have hairy; and feather- like projections; that increase the surface area; for them to be carried away by air currents and dropped far from the parent e.g. sonchus sp and cotton
Some fruits and seeds have wing-like structures;e.g. jacaranda, sycamore, tridax and nandi flame. Extensions increase the surface area; so that they are easily carried away by air currents;
- Censor mechanism
Some fruits are capsule- shaped; Some have pores at the top;e.g tobacco split along lines of weakness. The capsule is attached to a long stalk; hence when swayed by the wind.the seeds are released and scattered away from the parent plant;
- Self dispersal
This method occurs in legumes. When the pod dries up; the seeds break off from the placenta; The pod opens along the lines of weakness throwing seeds away from the parent; e.g. beans, castor oil, peas, crotalaria
Any 1 point with explanation 2 mks i.e. 1 point 1 mark. Explanation 1 mark. (10x2=20 mks)
PAPER 2 BIOLOGY . Q &A
1. Study the diagram below and answer the questions that follow.
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a) Name the parts labeled A,B,C, and D.
A - Trachea
B - Bronchus
C – Pleural membranes
D – Bronchioles
b) State the function of the fluid found between the parts marked C.
Reduce friction making the lungs to move freely in the chest cavity
c) How is the part labeled E adapted to its function.
- Moist
a. Highly supplied with blood capillaries
b. Enclosed by thin membrane
c. Numerous – large surface area
d) State the significance of rings of cartilage found around the part marked A and B.
prevent it from collapsing during breathing
2. a) State three functions of cerebrum.
- Integration of sensory impulses such as vision, hearing and taste;
- Controls voluntary body movements e.g. limbs, lips and neck;
- Controls learning memory and human individuality;
b) (i) Name the fluid found in the cavities of the brain:
Cerebrospinal fluid;
(ii) State the function of the fluid named in b(i) above;
(ii) - Provides nourishment (to brain tissues);
- Serves as a shock absorber from mechanical damage
(iii) In which layer of the meninges do we, find the fluid named in b(i) above.
Arachnoid layer;
iv) State two other components of the meninges and describe their location.
(iii) - The dura matter – tough outer most membrane;
- The pia matter – inner most membrane;
3. a) In a certain family with two children, one child was of blood group A while the other is blood group O. Work out the genotype of the two children, if the mother is blood group B and the father is blood group A.
B O A O;
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B O A O ;
AB BO AO OO;
AO, OO;
b) Below is a drawing of chromosomes of human and the genes located on it. Use the drawing to answer the questions that follow.
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4. a) Define the term Denature.
denature – change in protein structure so that some of its original properties/configuration stop functioning;
b) In an experiment to investigate the action of pepsin on egg albumen, equal amount of pepsin were added to equal amounts of egg albumen in different test-tubes. The test tubes were placed in water baths at different temperatures. The graph below shows time taken for the enzyme to digest protein in each .
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i) What is the optimum temperature for the enzyme?
Optimum temperature 36 + 1
ii) Account for the time taken to digest egg albumen at 450C.
At 45º C time taken is more than at 35º C because the enzyme/ pepsin is being denatured;
c) (i) In which form is the enzyme pepsin secreted.
Pepsinogen;
(ii) Give a reason for your answer in c (i) above.
digest stomach/ digest lumen in its active form (pepsin) in absence of protein food;
d) Name four plant tissues which lack chloroplast.
epidermal tissue
parenchyma;
Schlerenchyma;
Xylem tissue;
Collenchyma
e) State the function of the pad of gum in herbivorous feeding.
d) Provides surface on which food /grass is pressed and cut:
5. The diagram below represents the pathway of water from the soil into the plant.
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a) Name the structures labeled K and L.
. K. - Root hair;
L – xylem vessel
b) Explain how water from the soil reaches the structure labeled L.
- Water moves from the soil into the root hair by Osmosis;
- Because concentration of cell sap is higher than water in the soil;
- The cell sap in the root hair get diluted;
- Thus making it less concentrated than neighbouring cell;
- Therefore water moves into the neighbouring cells;
- It is actively separated into structure
c) Name the process by which mineral salts enter into the plant.
Active transport
acc diffusion
SECTION B (40 MARKS)
Answer question 6 (compulsory) and either question 7 or 8 in the spaces provided.
6. The glucose level in mg per 100ml of blood of two people A and B; who had been fasting for 12 hours was determined. The people were then fed on equal amounts of glucose and the levels of glucose determined at 30 minutes intervals for two hours. The results were as shown
in the table below.
Time in Minutes
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-
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0
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30
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60
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90
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120
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Blood Glucose (mg/100ml of blood)
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A
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157
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184
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194
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187
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180
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B
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90
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118
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125
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108
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84
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a) Using a suitable scale, draw a graph of blood glucose (mg/100ml) ) of blood against time in minutes.
Axis - 1mk
Scale - 2mks
Plotting - 2mks
Curve - 2mks
Label - 1mk
b) Account for the level of glucose in person B.
(i) during the first 30 minutes.
Blood glucose rose; (to over 100 mg/100 ml/ to about 120 mg/ 100ml) glucose is absorbed from the gut/liver has not yet converted excess glucose to glycogen
(ii) between 60 and 120 minutes.
Blood glucose declines to normal level/ about 85 mg/100ml; due to excess glucose being converted into glycogen; which is influenced by insulin; some of the glucose is used for respiration/ metabolism
(c ) Account for the glucose level in person A at the end of the two hours.
The person is (severely) diabetic (mellitus) hyperglycemia; due to lack of insulin/ pancrease damaged; glucose is not converted to glycogen; the slight fall is due to excretion;
d) If the normal glucose level in a healthy person is between 80 and 100mg per 100ml of blood, which one of the graphs represents the data for a person who is
(i) Healthy
C;
(ii) Severely diabetic
B;
7. Explain how the following types of plants are adapted to their habitats
(i) Xerophytes
Xerophytes
- Root extensively developed; to provide large S. A
- root grow deep/ long roots; to reach water source deep in the ground;
- succulent/ possession of water storage tissues; to store water / to survive drought;
- possession of thick waxy cuticle; to reduce rate of transpiration;
- hairy leave;
- sunken stomata;
- reduced leave sizes / spines/ scales/ thorns/ needle like/ reduced number of stomata;
- rolled leaves/ folded leaves shedding leaves;
- reversed stomata rhythm
- short life cycle/ quick growth after rains; to make use of the available water quickly;
(ii) Hydrophytes
(ii) Hydrophytes
- Air spaces/ large intercellular spaces/ aerenchyma tissue/ long fibrous roots;
- For buoyancy to float in water/ mineral absorption
- Poor developed conducting tissues/ xylem and phloem;
- Plants obtain water by diffusion.
- Poor developed supporting tissues/ schlerenchyma;
- Because water provides the necessary support
8. Describe how a male reproductive system is adapted to its functions.
The penis: it is spongy with large spaces that becomes gouged with blood causing it to erect;
The glands of the penis is highly sensitive due to nerve supply; and during copulation it is easily stimulated to bring about erection and ejaculation;
The penis is highly supplied with blood capillaries; that supply enough blood to the spongy spaces for erection;
The scrotum; is a sac like skin that suspends the testis outside the body at a lower temperature than that of the body ideal for spermatogenesis; the testis; contains numerous seminiferous tubules that nourish the sperms until they become mature; the epididymis; is long and coiled; to provide a large surface area for temporary storage of sperms;
The vas deferens; is muscular and upon contraction of its muscles it pushes sperms out and allows ejaculation;
The accessory glands like seminal vesicles; cowpers gland; and prostrate glands; provided fluids / seminal fluids that nourish spermatozoa; and provide it with a suitable swimming medium;
