SAMPLE PAPER 1 231/1 1
1. (a) In sheep, the number of chromosomes in mature egg cells is 28. How many chromosomes are found in the somatic cell of sheep? (1 mark) …………………………………………………………………………………………………..
(b) Which cells are haploid and triploid in the life cycle of a typical flowering plant? (2mark)2 …………………………………………………………………………………………………………
2. A mammoth has become extinct with time. Give two reasons why it became extinct. (2 marks)5 ……………………………………………………………………………………………………………………………………………………………………………………………………………………
3. Differentiate between dormancy and hibernation. (1 mark)6
………………………………………………………………………………………………….
4. What is the importance of genetic variations in evolution? (3 marks)9
……………………………………………………………………………………………………………………………………………………………………………………………………………………
5. Blood transfusion of Rh+ve blood was given to a patient with Rh- blood. After one week, a similar transfusion was given to the same patient. What was likely to happen the effect on the second transfusion? (3 marks) 12
……………………………………………………………………………………………………………………………………………………………………………………………………………………
6. Give two adaptations developed by water lettuce, Pistia sp. to floating in aquatic habitat.
(2 marks) 14
……………………………………………………………………………………………………………………………………………………………………………………………………………………
7. Differentiate between a back cross and a test cross. (2 marks)16
…………………………………………………………………………………………………………
8. Explain how consumption of excess carbohydrates and proteins leads to an increase in weight. (4 marks)20
……………………………………………………………………………………………………………………………………………………………………………………………………………………
9. A biologist observed a living cell in a culture shown below:
(i) Name the group of organisms the cell belongs. (1 mark) 21
……………………………………………………………………………………………….
(ii) Give two reasons for your answer. (2 marks)23
………………………………………………………………………………………………………………………………………………………………………………………………
10. What is the role of juvenile hormone in metamorphosis of insects? (1 mark) 24
…………………………………………………………………………………………………
11. Classify the locusts in the two taxa shown below: (2 marks)26
Phylum: ………………………………………………………………………………………………….
Class: …………………………………………………………………………………………………
12. Identify the relationship that exists between the following organisms.
(i) Nitrogen fixing bacteria and leguminous plants. (1 mark) 27
……………………………………………………………………………………………….
(ii) Plasmodium and human. (1 mark) 28
………………………………………………………………………………………………
13. (i) What is osmoregulation? (1 mark) 29
…………………………………………………………………………………………………
(ii) Name the two organs in mammalian body that carry out osmoregulation. (2 marks)31
………………………………………………………………………………………………………………………………………………………………………………………………
14. Why is cell turgidity important to herbaceous plants? (2 marks)33
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
15. Explain why the white blood cells usually don’t undergo haemolysis although they are found suspended in plasma. (2 marks)35
……………………………………………………………………………………………………………………………………………………………………………………………………
16. A research station grows a bean crop to produce seeds for sale to farmers. Give three characteristics the researcher would want to establish in their breeding programme. (3 marks)38
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
17. In a lecture on gene mutations, the following analogy was made regarding an SMS:
Intended message: Paul now arriving at Mombasa.
Actual message: Paul not arriving at Mombasa.
What type of gene mutation was being illustrated by the analogy? (1 mark) 39
…………………………………………………………………………………………………
18. Examination of electron micrographs of a section of an animal tissue showed that the following features: Cells more or less isodiametric, each contained a large spherical and prominent nucleolus, many mitochondria, Golgi apparatus, endoplasmic reticula and granular materials identified as glycogen. Between the cells were bile canaliculi.
(a) From which organ was the tissue obtained? (1 mark)40
……………………………………………………………………………………………….
(b) State the main function of Golgi apparatus. (1 mark)41
………………………………………………………………………………………………
19. Match the terms A, B and C with R, Q, P and T below according to the best description. Write your answer in the spaces after the table. (3 marks)44
A: Autotrophism
B: Heterotrophism
C: Phagocytism
R: Engulfing and digesting food using lytic enzymes in food vacuoles.
Q: Feeding on other organisms but not killing them.
T: Manufacturing one’s own food from simple substances
P: Depending on food manufactured by others
A: …………………………………………………………………………………………………..
B: …………………………………………………………………………………………………..
C: …………………………………………………………………………………………………..
20. What are the function of the following parts of a microscope? (2 marks) 46
(a) Mirror: ………………………………………………………………………………………………
(b) Revolving nose piece: ………………………………………………………………………………………………
21. What is the role of water in seed germination of flowering plants? (3 marks)49
……………………………………………………………………………………………………………………………………………………………………………………………………………………
22. Bean plants that produce brown coloured seeds were crossed with bean plants that produce white coloured seeds. The first generation of the cross produced brown coloured seeds only. Give a reason why there were no white coloured seeds in the first generation. (1 mark) 50
……………………………………………………………………………………………………………………………………………………………………………………………………
23. What is the source of oxygen found in carbohydrates molecules? (1 mark) 51
…………………………………………………………………………………………………
24. A student observed two types of cells, P and Q under an electron microscope.
P-- was small and biconconcave. Nucleus was missing.
Q-- was colourless, larger than P, had a bilobed nucleus and had no definite shape.
Identify the types of cells. (2 marks)53
P: …………………………………………………………………………………………………
Q:
………………………………………………………………………………………………….
25. Briefly explain what you understand by the term double fertilization. (3 marks) 56
…………………………………………………………………………………………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………………………………………………………………………..
26. Suggest a reason for each of the following statements.
(a) A pregnant woman requires more protein than an active man. (1 mark)57
…………………………………………………………………………………………….
…………………………………………………………………………………………….
(b) Adolescent girls require more iron than boys of the same age. (1 mark)58
…………………………………………………………………………………………………………
27. Removal of the apical bud from a shrub is a practice that results in the development of many lateral buds which later form branches. Give reasons for the development of lateral branches after the removal of the apical bud. (2 marks)60
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
28. What are the characteristics of the following?
(i) Leukemia? (1 mark) 61
…..……………………………………………………………………………………………..
(ii) Anaemia? (1 mark)62
………………………………………………………………………………………………….
29. Describe how deamination takes place? (3 marks) 65
…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
30. The diagram below represents a life cycle of an insect.
(i) Name the type of metamorphosis in insects represented by the following diagram.
(1 mark)66
………………………………………………………………………………………………..
(ii) Which stage is dormant? (1 mark)67
……………………………………………………………………………………………….
31. Name two components of balanced diet that are absorbed without being digested.
2 marks) 69
…………………………………………………………………………………………………………
32. Kangaroo rats (Dipodymis) are in fact rodents and not marsupials which live in the desert where years may elapse between rainfalls. They live on seeds and other dry plant material, and eat little or no green and succulent food. They search for these grains at night. Give two adaptive reasons why it is possible for these animals to survive in such harsh environmental conditions without water. (2 marks)71
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….
33. Name two factors that affect the rate of diffusion. (2 marks)73
……………………………………………………………………………………………………………………………………………………………………………………………………
34. (i) What causes tooth decay? (2 marks) 75
………………………………………………………………………………………………….
(ii) Name an element in the diet necessary for the formation of teeth in human beings.
(1 mark)76
…………………………………………………………………………………………………...
35. Differentiate between a prey and a predator. (2 marks) 78
………………………………………………………………………………………………………………………………………………………………………………………………….....
36. Name the tissues whose cells are thickened with:
a) Cellulose and pectin.
…………………………………………………... (1mk)79
b) Lignin. (1mk)80
………………………………………………………………
MARKING SCHEME
PAPER 231/1
1. (a) 56;
(b) Haploid: Pollen grain nuclei – generative nucleus and tube nucleus and Egg cell
(Oosphere); Triploid: Primary endosperm nucleus;
2. Large in size than it could be supported; Coordination system like nervous system was not efficient; Competition with other better adapted animals; Change in climate resulting to inability to control temperature; Change in vegetation e.g. from Pteridophyte to Angiosperm meant no food; [mark 1st 2]
3. Dormancy is a period of quiescent/ rest when there is little growth in seeds particularly; while hibernation is a period of rest an organism undergoes to escape hot weather condition;
4. Brings about a change in genetic equilibrium; by increasing/ decreasing the frequency of certain genes; if environment changes, the selection pressure is altered in favour of a particular gene;
5. Antibodies against Rh+ factor produced after first transfusion; red blood cells of second dose would be made to clump/ clot; which may result to death;
6. Broad leaves giving flattened surfaces to aid in floating, photosynthesis and transpiration; Long/flexible petioles that allow the leaves to move freely within the water;
Stomata on the upper side of the leaf only to allow gaseous exchange and transpiration.
Air spaces/ aerenchymatous tissue to store air for buoyancy/ to allow gaseous exchange;
Fibrous roots to promote buoyancy [mark 1st 2]
7. A back cross involves crossing a hybrid with either of its parents in order to achieve offspring with genetic identity closer to that of the parent; while a test cross involves crossing an individual having a dominant phenotype with a double recessive parent as to identify if its genotype is heterozygous or homozygous;
8. Their excess results in excess availability of glucose and keto group; which is converted to free fatty acids; that combine with glycerol to form fats; These fats are stored in adipose tissue thus increasing body weight;
9. (i) Bacteria; Monera; Prokaryotic
(ii) Organelles which are not membrane-bound; Lack of mitochondria; Reproduce by binary fission; [mark 1st 2]
10. Prolongs larval stage;
11. Phylum: Arthropoda: Class: Insecta;
12. (i) Symbiotism;
(ii) Parasitism;
13. (i) Maintenance of constant osmotic pressure of body fluids/ blood and tissue fluid; (ii) Kidney; Liver;
14. Mechanical support; Maintenance of shape;
15. Their cytoplasm is isotonic to plasma; thus, no net osmosis/ movement of water in and out of the cell;
16. Productivity; Pest resistance; Disease resistance; Drought resistance; Quick maturity;
17. Substitution;
18. (a) Liver; (b) Secrete, package and transports secretions like glycoproteins; Production of lysosomes; [mark 1st 2]
19. A: T; B: P; C: R;
20. Mirror: Reflect light to through the object to the eye of the viewer
Revolving nose piece: Select the desired objective lens;
21. Hydrolysis; Activation of germination enzymes; Softening of seed coat; Medium of chemical reactions; Mobilization of soluble food; [mark 1st 2]
22. The gene for brown colour is dominant over the gene for white colour;
23. Carbon (IV) oxide/ CO2;
24. P: Red blood cell; Q: white blood cell;
25. The one in which one haploid male gamete nucleus fuses with the haploid nucleus of functional egg cell; to form a diploid zygote; while the other haploid male gamete nucleus fuses with haploid polar nuclei; to form triploid primary endosperm nucleus;
26. (a) The embryo obtains amino acids for growth from the mother; Active man requires more carbohydrates than proteins for energy production;
(b) After puberty, the adolescent girl has menstrual flow after every 28 days, thus more iron needed for synthesizes of haemoglobin in the red blood cells to replace the lost ones/ to raise the haemoglobin level of the blood;
27. Apical bud produces auxins/ hormones/ a growth substance; which inhibits the development/ growth of lateral shoots/ buds/ apical dominance;
28. (i) Abnormal high number of WBCs; Acc. over production of WBCs. Rej. Blood cancer. (ii) Low number of RBCs/ low blood volume. Acc. insufficient RBCs, low levels of haemoglobin and RBCs. Rej. lack of RBCs, lack of haemoglobin; lack of iron.
29. Excess amino acids/proteins; are transported to the liver.
Deamination; process of removal of an amino group from an amino acid molecule occurs;
The process gets rid of excess amino acids in the body; as the body is not able to store them;
The amino group enters the ornithine cycle; where it is combined with carbon (IV) oxide to form urea. (3m)
30. (i) Complete/
(ii) D;
31. Mineral salts; water; vitamins; [mark 1st one]
32. They use metabolic water; They do not sweat; They are nocturnal; Their faeces have very little water; They produce hypertonic urine; Their water loss does not exceed their water gain; long loops of Henle to maximize water reabsorption [mark 1st 2]
33. Concentration gradient; Temperature; Size of molecules; Surface area to volume ration; Thickness of tissue/ membrane; Agitation; [mark 1st 2]
34. (i) Bacteria in the mouth fermenting food remains; forming acid that attacks and dissolves tooth enamel;
(ii) Calcium/ Phosphorus;
35. A predator is an organism that hunts, kills and feeds on another organism; which is called a prey;
36. Collenchyma;
Sclerenchyma; vessels; tracheids
(b) Which cells are haploid and triploid in the life cycle of a typical flowering plant? (2mark)2 …………………………………………………………………………………………………………
2. A mammoth has become extinct with time. Give two reasons why it became extinct. (2 marks)5 ……………………………………………………………………………………………………………………………………………………………………………………………………………………
3. Differentiate between dormancy and hibernation. (1 mark)6
………………………………………………………………………………………………….
4. What is the importance of genetic variations in evolution? (3 marks)9
……………………………………………………………………………………………………………………………………………………………………………………………………………………
5. Blood transfusion of Rh+ve blood was given to a patient with Rh- blood. After one week, a similar transfusion was given to the same patient. What was likely to happen the effect on the second transfusion? (3 marks) 12
……………………………………………………………………………………………………………………………………………………………………………………………………………………
6. Give two adaptations developed by water lettuce, Pistia sp. to floating in aquatic habitat.
(2 marks) 14
……………………………………………………………………………………………………………………………………………………………………………………………………………………
7. Differentiate between a back cross and a test cross. (2 marks)16
…………………………………………………………………………………………………………
8. Explain how consumption of excess carbohydrates and proteins leads to an increase in weight. (4 marks)20
……………………………………………………………………………………………………………………………………………………………………………………………………………………
9. A biologist observed a living cell in a culture shown below:
(i) Name the group of organisms the cell belongs. (1 mark) 21
……………………………………………………………………………………………….
(ii) Give two reasons for your answer. (2 marks)23
………………………………………………………………………………………………………………………………………………………………………………………………
10. What is the role of juvenile hormone in metamorphosis of insects? (1 mark) 24
…………………………………………………………………………………………………
11. Classify the locusts in the two taxa shown below: (2 marks)26
Phylum: ………………………………………………………………………………………………….
Class: …………………………………………………………………………………………………
12. Identify the relationship that exists between the following organisms.
(i) Nitrogen fixing bacteria and leguminous plants. (1 mark) 27
……………………………………………………………………………………………….
(ii) Plasmodium and human. (1 mark) 28
………………………………………………………………………………………………
13. (i) What is osmoregulation? (1 mark) 29
…………………………………………………………………………………………………
(ii) Name the two organs in mammalian body that carry out osmoregulation. (2 marks)31
………………………………………………………………………………………………………………………………………………………………………………………………
14. Why is cell turgidity important to herbaceous plants? (2 marks)33
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
15. Explain why the white blood cells usually don’t undergo haemolysis although they are found suspended in plasma. (2 marks)35
……………………………………………………………………………………………………………………………………………………………………………………………………
16. A research station grows a bean crop to produce seeds for sale to farmers. Give three characteristics the researcher would want to establish in their breeding programme. (3 marks)38
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
17. In a lecture on gene mutations, the following analogy was made regarding an SMS:
Intended message: Paul now arriving at Mombasa.
Actual message: Paul not arriving at Mombasa.
What type of gene mutation was being illustrated by the analogy? (1 mark) 39
…………………………………………………………………………………………………
18. Examination of electron micrographs of a section of an animal tissue showed that the following features: Cells more or less isodiametric, each contained a large spherical and prominent nucleolus, many mitochondria, Golgi apparatus, endoplasmic reticula and granular materials identified as glycogen. Between the cells were bile canaliculi.
(a) From which organ was the tissue obtained? (1 mark)40
……………………………………………………………………………………………….
(b) State the main function of Golgi apparatus. (1 mark)41
………………………………………………………………………………………………
19. Match the terms A, B and C with R, Q, P and T below according to the best description. Write your answer in the spaces after the table. (3 marks)44
A: Autotrophism
B: Heterotrophism
C: Phagocytism
R: Engulfing and digesting food using lytic enzymes in food vacuoles.
Q: Feeding on other organisms but not killing them.
T: Manufacturing one’s own food from simple substances
P: Depending on food manufactured by others
A: …………………………………………………………………………………………………..
B: …………………………………………………………………………………………………..
C: …………………………………………………………………………………………………..
20. What are the function of the following parts of a microscope? (2 marks) 46
(a) Mirror: ………………………………………………………………………………………………
(b) Revolving nose piece: ………………………………………………………………………………………………
21. What is the role of water in seed germination of flowering plants? (3 marks)49
……………………………………………………………………………………………………………………………………………………………………………………………………………………
22. Bean plants that produce brown coloured seeds were crossed with bean plants that produce white coloured seeds. The first generation of the cross produced brown coloured seeds only. Give a reason why there were no white coloured seeds in the first generation. (1 mark) 50
……………………………………………………………………………………………………………………………………………………………………………………………………
23. What is the source of oxygen found in carbohydrates molecules? (1 mark) 51
…………………………………………………………………………………………………
24. A student observed two types of cells, P and Q under an electron microscope.
P-- was small and biconconcave. Nucleus was missing.
Q-- was colourless, larger than P, had a bilobed nucleus and had no definite shape.
Identify the types of cells. (2 marks)53
P: …………………………………………………………………………………………………
Q:
………………………………………………………………………………………………….
25. Briefly explain what you understand by the term double fertilization. (3 marks) 56
…………………………………………………………………………………………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………………………………………………………………………..
26. Suggest a reason for each of the following statements.
(a) A pregnant woman requires more protein than an active man. (1 mark)57
…………………………………………………………………………………………….
…………………………………………………………………………………………….
(b) Adolescent girls require more iron than boys of the same age. (1 mark)58
…………………………………………………………………………………………………………
27. Removal of the apical bud from a shrub is a practice that results in the development of many lateral buds which later form branches. Give reasons for the development of lateral branches after the removal of the apical bud. (2 marks)60
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
28. What are the characteristics of the following?
(i) Leukemia? (1 mark) 61
…..……………………………………………………………………………………………..
(ii) Anaemia? (1 mark)62
………………………………………………………………………………………………….
29. Describe how deamination takes place? (3 marks) 65
…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
30. The diagram below represents a life cycle of an insect.
(i) Name the type of metamorphosis in insects represented by the following diagram.
(1 mark)66
………………………………………………………………………………………………..
(ii) Which stage is dormant? (1 mark)67
……………………………………………………………………………………………….
31. Name two components of balanced diet that are absorbed without being digested.
2 marks) 69
…………………………………………………………………………………………………………
32. Kangaroo rats (Dipodymis) are in fact rodents and not marsupials which live in the desert where years may elapse between rainfalls. They live on seeds and other dry plant material, and eat little or no green and succulent food. They search for these grains at night. Give two adaptive reasons why it is possible for these animals to survive in such harsh environmental conditions without water. (2 marks)71
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….
33. Name two factors that affect the rate of diffusion. (2 marks)73
……………………………………………………………………………………………………………………………………………………………………………………………………
34. (i) What causes tooth decay? (2 marks) 75
………………………………………………………………………………………………….
(ii) Name an element in the diet necessary for the formation of teeth in human beings.
(1 mark)76
…………………………………………………………………………………………………...
35. Differentiate between a prey and a predator. (2 marks) 78
………………………………………………………………………………………………………………………………………………………………………………………………….....
36. Name the tissues whose cells are thickened with:
a) Cellulose and pectin.
…………………………………………………... (1mk)79
b) Lignin. (1mk)80
………………………………………………………………
MARKING SCHEME
PAPER 231/1
1. (a) 56;
(b) Haploid: Pollen grain nuclei – generative nucleus and tube nucleus and Egg cell
(Oosphere); Triploid: Primary endosperm nucleus;
2. Large in size than it could be supported; Coordination system like nervous system was not efficient; Competition with other better adapted animals; Change in climate resulting to inability to control temperature; Change in vegetation e.g. from Pteridophyte to Angiosperm meant no food; [mark 1st 2]
3. Dormancy is a period of quiescent/ rest when there is little growth in seeds particularly; while hibernation is a period of rest an organism undergoes to escape hot weather condition;
4. Brings about a change in genetic equilibrium; by increasing/ decreasing the frequency of certain genes; if environment changes, the selection pressure is altered in favour of a particular gene;
5. Antibodies against Rh+ factor produced after first transfusion; red blood cells of second dose would be made to clump/ clot; which may result to death;
6. Broad leaves giving flattened surfaces to aid in floating, photosynthesis and transpiration; Long/flexible petioles that allow the leaves to move freely within the water;
Stomata on the upper side of the leaf only to allow gaseous exchange and transpiration.
Air spaces/ aerenchymatous tissue to store air for buoyancy/ to allow gaseous exchange;
Fibrous roots to promote buoyancy [mark 1st 2]
7. A back cross involves crossing a hybrid with either of its parents in order to achieve offspring with genetic identity closer to that of the parent; while a test cross involves crossing an individual having a dominant phenotype with a double recessive parent as to identify if its genotype is heterozygous or homozygous;
8. Their excess results in excess availability of glucose and keto group; which is converted to free fatty acids; that combine with glycerol to form fats; These fats are stored in adipose tissue thus increasing body weight;
9. (i) Bacteria; Monera; Prokaryotic
(ii) Organelles which are not membrane-bound; Lack of mitochondria; Reproduce by binary fission; [mark 1st 2]
10. Prolongs larval stage;
11. Phylum: Arthropoda: Class: Insecta;
12. (i) Symbiotism;
(ii) Parasitism;
13. (i) Maintenance of constant osmotic pressure of body fluids/ blood and tissue fluid; (ii) Kidney; Liver;
14. Mechanical support; Maintenance of shape;
15. Their cytoplasm is isotonic to plasma; thus, no net osmosis/ movement of water in and out of the cell;
16. Productivity; Pest resistance; Disease resistance; Drought resistance; Quick maturity;
17. Substitution;
18. (a) Liver; (b) Secrete, package and transports secretions like glycoproteins; Production of lysosomes; [mark 1st 2]
19. A: T; B: P; C: R;
20. Mirror: Reflect light to through the object to the eye of the viewer
Revolving nose piece: Select the desired objective lens;
21. Hydrolysis; Activation of germination enzymes; Softening of seed coat; Medium of chemical reactions; Mobilization of soluble food; [mark 1st 2]
22. The gene for brown colour is dominant over the gene for white colour;
23. Carbon (IV) oxide/ CO2;
24. P: Red blood cell; Q: white blood cell;
25. The one in which one haploid male gamete nucleus fuses with the haploid nucleus of functional egg cell; to form a diploid zygote; while the other haploid male gamete nucleus fuses with haploid polar nuclei; to form triploid primary endosperm nucleus;
26. (a) The embryo obtains amino acids for growth from the mother; Active man requires more carbohydrates than proteins for energy production;
(b) After puberty, the adolescent girl has menstrual flow after every 28 days, thus more iron needed for synthesizes of haemoglobin in the red blood cells to replace the lost ones/ to raise the haemoglobin level of the blood;
27. Apical bud produces auxins/ hormones/ a growth substance; which inhibits the development/ growth of lateral shoots/ buds/ apical dominance;
28. (i) Abnormal high number of WBCs; Acc. over production of WBCs. Rej. Blood cancer. (ii) Low number of RBCs/ low blood volume. Acc. insufficient RBCs, low levels of haemoglobin and RBCs. Rej. lack of RBCs, lack of haemoglobin; lack of iron.
29. Excess amino acids/proteins; are transported to the liver.
Deamination; process of removal of an amino group from an amino acid molecule occurs;
The process gets rid of excess amino acids in the body; as the body is not able to store them;
The amino group enters the ornithine cycle; where it is combined with carbon (IV) oxide to form urea. (3m)
30. (i) Complete/
(ii) D;
31. Mineral salts; water; vitamins; [mark 1st one]
32. They use metabolic water; They do not sweat; They are nocturnal; Their faeces have very little water; They produce hypertonic urine; Their water loss does not exceed their water gain; long loops of Henle to maximize water reabsorption [mark 1st 2]
33. Concentration gradient; Temperature; Size of molecules; Surface area to volume ration; Thickness of tissue/ membrane; Agitation; [mark 1st 2]
34. (i) Bacteria in the mouth fermenting food remains; forming acid that attacks and dissolves tooth enamel;
(ii) Calcium/ Phosphorus;
35. A predator is an organism that hunts, kills and feeds on another organism; which is called a prey;
36. Collenchyma;
Sclerenchyma; vessels; tracheids
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