CCHY 2013 Bio Yearly TYS ANS

6093 Biology Yearly TYS 2013 No Paper 1 Marks Remarks 1 B 1 2 C 1 3 C 1 4 D 1 5 D 1 6 A 1 7 D 1 8 C 1 9 D 1 10 C 1 11 C 1 12 D 1 13 A 1 14 A 1 15 D 1 16 B 1 17 C 1 18 C 1 19 B 1 20 D 1 21 D 1 22 B 1 23 A 1 24 C 1 25 B 1 26 B 1 27 B 1 28 A 1 29 B 1 30 B 1 31 B 1 32 B 1 33 D 1 34 C 1 35 C 1 36 B 1 37 B 1 38 A 1 change option A to 23 + 1X for chromosomes in ovum 39 B 1 40 A 1 Total 40

Paper 2 Section A 1ai P: right atrium Q: bicuspid valve/ chordae tendineae 1 1 1aii Line drawn pointing to aorta with label X 1 1b Oxygenated blood from lungs flows into LA through pulmonary veins; muscles of LA contract increasing P(LA)+ When P(LA) is higher than P(LV), bicuspid valves open allowing blood to flow from LA to LV; muscles of LV contract increasing P(LV)+ when P(LV) is higher that P(LA) bicuspid valves closes to prevent backflow of blood into LA; When P(LV) is higher than P(aorta), semilunar valves open to force out of LV into aorta at high pressure , transported to all parts of the body; When P(aorta) is higher in P(LV), semilunar valves closes to prevent backflow of blood into LV; 1 1 1 1 Entry of blood into heart Atrial contraction Ventricular systole Closure of valves R: atrium contract A: muscles of the atrium contracts 1ci P(LV) = Line 2 P(LA) = Line 3 P(aorta) = Line 1 P(LV) > P(LA) = 0.1 P(LV) < P(aorta) = 0.4 0.4 – 0.1 = 0.3s 1 1cii Line 2 1 Total 9

2a Translocation is the transport of m anufactured food substances such as sucrose and amino acids by active transport; Occurs through the phloem from the leaves to the other parts of the plants vice versa/ bi-directional; 1 1 substances process location direction 2bi Left side beside the cambium nearer to pith 1 2bii Right side, darker region nearer to epidermis 1 2c Weed killers are soluble in water / dissolves in water in soil; weed killer diffuse into the root hair cells down concentration gradient + diffuse from RHC into t he adjacent root cells down concentration gradient until the xylem; weed killers move u p the xylem vessel in the stem by transpiration pull; Weed killer reaches the x ylem vessel in the leaf veins + reaching the chloroplasts in the mesophyll cells in the leaf; 1 1 1 1 solubility soil to RHC to RC to xylem process xylem to leaf to MC Total 8

3a P: branch of renal artery 1 3bi Protein content: 0.0 Glucose content: 0.1 1 1 3bii Proteins are present in P but not in R + at glomerulus, proteins are retained in the glomerular capillaries; they are too large to pass through the walls of the glomerular capillaries and the partially permeable basement membrane + no proteins in R; 1 1 3biii Absence of glucose in R + at PCT, most glucose are selectively reabsorbed through the walls of the tubule into the surrounding blood capillaries by diffusion and active transport; 1 3c Increase water potential above normal level in blood plasma stimulates hypothalamus in the brain to trigger pituitary gland to release less ADH into bloodstream; Less ADH stimulates cells in the walls of the collecting ducts to become less permeable to water + less water reabsorbed from the collecting duct into the blood capillaries; Larger volume of urine + urine produced is more diluted; / decrease water potential below normal level in blood plasma stimulates hypothalamus in the brain to trigger pituitary gland to release more ADH into bloodstream; more ADH stimulates cells in the walls of the collecting ducts become more permeable to water + more water reabsorbed from the collecting d uct into the blood capillaries; smaller volume of urine + urine produced is more concentrated; 1 1 1 Stimulus Total 9

4a Energy needed to start a chemical reaction + lowered in the presence of enzymes 1 4bi Boiling tube 1: Protease digests proteins/gelatine into polypeptides + protease works best/most active/ rate of reaction of protease is the highest in acidic medium; Gelatine layer breaks down + silver particles are released into the water forming a suspension; Boiling tubes 2 and 3: In boiling tube 2, protease cannot digest proteins in neutral pH + in boiling tube 3, protease cannot digest proteins in akaline pH because enzymes are denatured + active site altered + e-s complex not formed + no enzyme reaction; Gelatine layer did not break down + silver particles are not released into the water; 1 1 1 1 Effect of pH on enzyme Effect of enzyme Effect of pH on enzyme Effect of enzyme 4bii Temperature of each boiling tube/ Volume of water in each boiling tube/ Length of photographic film/ Amount of time taken to conduct experiment/ Volume of protease solution in each boiling tube 2 Any 2 Total 7 5a microscopic green plants  zooplankton  small fish  carnivorous fish  large carnivorous birds 1 1 5bi microscopic green plants + water plants 1 5bii Producer such as water plants and microscopic green plants provide other organisms with energy and oxygen; Contain chlorophyll which traps and convert light energy into chemical energy; photosynthesise to synthesise glucose from carbon dioxide and water + produce oxygen as a by-product; 1 1 1 Total 6

6a 1: Bb; Reason: both parents 1 and 2 have a genotype that is in a heterozygous condition because they are brown-eyed and has a daughter (individual 5) who inherits one recessive allele from each parent; 10: Bb Reason: Individual 4 is homozygous recessive (bb) blue-eyed, so individual 10 who is brown -eyed must be heterozygous Bb as he inherit a dominant allele from mother and recessive allele from father; 1 1 1 1 6b 2, 6, 8, 10 1 6c Discontinuous variation 1 Total 6 7ai Hormones are chemical substances produced in minute/small amounts by an endocrine gland + transported by the blood to target organs; hormones influences growth, development and activity of an organism; after hormone performed its function + destroyed by the liver; 1 1 1 describe mode of transmission effect of hormones after 7aii Transport milk from the glands to the nipple 1 7b Add sugar into the cow’s milk 1 Total 5

Section B 8a Axes labelled correctly + equal intervals + correct orientation; All points plotted correctly; Best fit line; Graph occupies at least 2/3 of grid; 4 8bi 700mm 1 8bii 15 kJ per kg per hour 1 8biii Mean rate of heat production decreases with increasing mean body length 1 8c Aerobic respiration 1 8d When blood and skin temperature increases above normal level, temperature receptors in the skin detects the change produce nerve impulses sent to hypothalamus in brain that stimulates decrease in metabolic rate so as to reduce the amount of heat released; Arterioles in skin dilate + shunt vessels constrict + increase blood flow to capillaries in the skin + increasing heat lost by radiation, convection, conduction; Sweat glands becom e more active causing an increase in production of sweat + more water in sweat evaporates into water vapour, increasing heat loss by latent heat of vaporisation; 1 1 1 Total 11 0 5 10 15 20 25 30 200 400 600 800 1000 1200 1400 mean rate of heat production/ kJ per kg per hour mean body length/ mm Graph of Mean Rate of Heat Production against Mean Body Length

9a Transgenic organism is any organism which acquires a foreign gene; Genetic engineering is used to transfer genes from one organism to another + transfer of genes involved inserting the genes of interest into a vector; eg. Genes can be transferred from human cells to bacteri