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MUHORONI DISTRICT JOINT EVALUATION EXAM BIOLOGY PAPER 2 JULY/AUGUST 2014 MARKING SCHEME 1. (a) (i) Parental genotypes Gametes : Aa X A a Aa ; (1mk) A a ; (1mk) ;(1mk) F1 generation: 2. 3 Aa aa; (1mk) Aa (ii) ¼ OR 25% ; (b) Sickle cell anaemia; Colourblindness ; Haemophilia; (a) (b) To determine the rate of transpiration; (1mk) Cut the shoot under water to avoid blockage of xylem vessels by air. - Apply petroleum jelly between the cork/rubber bung and the glass, and between the rubber and shoot to make the apparatus air tight. - Open the reservoir tap when assembling to remove the air bubbles from the tubes - Assemble under water to ensure no air bubbles are enclosed; (1mk) (1mk) (1mk) (1mk) (c) Light ; temperature ; wind; humidity; atmospheric, pressure; (Any 3 mks) (d) In plasma - hydrogen carbonate; In red blood cells - carbanaminohaemoglobin; (2mks) bung (a) Osmosis; (b) Piece A - was placed in a hypotonic solution. The cortex inner cells gained water by osmosis; became turgid and increased in size/length. Epidermal cells are covered by a waterproof and inelastic cuticle hence did not gain water; leading to curvature outwards. (2mks) (c) (1mk) Piece B - was placed in hypertonic solution. Inner cortex cells lost water by osmosis, decreased in length. Epidermal cells did not lose water due to waterproof cuticle, leading to curvature inwards. (i) Absorption of water and mineral salts (1mk) (ii) 4. AA Micro-organisms present synthesize, vitamins K1 B2 and B2; (d) Sap Vacuole; (a) (b) (c) Photosynthesis; Carnivorous; Rej. canivores Aquatic (d) Terrestrial; Algae (e) (1mk) (1mk) Zooplanktons (1mk) (1mk) (1mk) Small fish Bird J Large bird (1mk) (1mk) More snails for bird M, hence increase in population of bird M; - Green plants reduce as are eaten by more snails; 1 ©Muhoroni District Form Four 2014 Biology Paper 2 - Population of large birds may remain constant/decrease/increase; (Accept any 3 correct answer = 1mk) (f). Energy is lost through Respiration;/Heat through radiation, conduction and convection ;egestion; excretion; (Accept any one = 1mk) (g). 5. (a) (b) (c) (d) (e) (a) Drawn on graph paper (6mks) Rate of Reaction 6. Pollution (accept named pollutants); - Farming (accept agrochemicals, pesticides, herbicides); - Fishing; - Deforestation, - Poaching/hunting (Accept any 1 correct answer 1mk) Primary Oocytes (1mk) (i) Germinal epithelium; (1mk) (ii) Mitosis; (1mk) (i) Oestrogen; (1mk) (ii) Healing and repair of the uterine wall following menstruation; Stimulates the pituitary glands to secrete lutetinising hormones;LH (Accept one correct named answer - 1mk) (i) Funnel/fallopian tube/oviduct (1mk) (ii) Luteinising hormone (1mk) Secretes the hormone progesterone which maintains the thickened uterine wall and hence pregnancy in the first three months. (1mk) Temperature (0C) (b) 36.50C ± 0.50C (c) 210C ± 0.50C (d) (i) 50C and 350C rapidly ©Muhoroni District Form Four 2014 (1mk) (1mk) As the temperature increased, rate of reaction increased 2 Biology Paper 2 because enzymes becames more active with increasing temperature within that range; (2mks) (ii) 380C and 500C As temperature increased rate of reaction decreased rapidly because the enzyme are getting denatured √ by the high temperatures. (3mks) (e) (f) (g) (h) 7. Through the action of sodium hydrogen carbonate; present in the pancreatic juice; secreted (within the duodenum). (2mks) Pepsin, Rennin (1mk) (Any correct 1 answer) High temperatures (1mk) Extreme of PH; (1mk) Bascal metabolic rate; Age; Occupation/Activity; sex; body size (Mark any two correct = 2mks) (i) Fossils study (Paleontology) Fossils describes ancestral forms of organisms that were accidentally preserved in naturally occurring materials such as sedimentary rocks and resins√. They provide direct evidence of gradual change from one type of organism to another√. They are preserved in sedimentary rocks in layers; lowest oldest layers contains oldest fossils while uppermost younger layers contains recent fossils √; Fossils show morphological changes of given organism over long period of time e.g human skull, leg of a horse. Earliest fossils were those of monera, followed by protoctista then fungi √; comparisonof fossils of different organisms may give phylogenetic relationship between organisms√. (ii) Homologous Structure (divergent evolution) Presence of homologous structures Implies same ancestry at some time of evolutionary history √; One structure can give rise various different forms - divergent evolution √ divergent forms from same ancestry become adapted to particular function - adaptive radiation √; examples are pentadactyl limbs present in vertebrates, beak structures in birds etc√. (Mark any 1 correct example after explanation) Analogous structures (Convergent evolution) The structures show how adaptation to similar environment can lead to a similarity in structure and function in unrelated organisms; examples wings of birds and wings of insects, eye structure of the humans and octopus√. (Mark any 1 correct example after explanation) (iii) Vestigial structures (organs) They have ceased to function or greatly reduced (rudimentary) in course of evolution √as were selected against as animals became adapted to different modes of life √. Example caecum and appendix in man, coccyx in man, nictitating eye membrane in mammals etc. (Mark any 1 correct example after explanation) (iv) Comparative Embryology Embryos of different vertebrate species have many common features, suggesting a common ancestry e.g all vertebrate embryos have tails √ all vertebrate have gill pouches at some development stage√. The closer the resemblance between the early stage of embryo the closer their evolutionary relationship (Recapitulation theory) √. Showing or indicating different ancestry/phylogeny (v) Cell biology and biochemistry All eukaryotic cells contains same cell organelles as mitochondria lysosomes etc and have chemicals like ATP,RNA,DNA, etc, indicating common ancestry. Blood pigments are of ©Muhoroni District Form Four 2014 3 Biology Paper 2 universal occurrences e.g haemolglobin, haemocyanin , thyolobin etc. Plant cells have cellulose cell wall chloroplast, sap vacuoles etc unlike animal cells√. (vi) 8. Comparative Serology Blood proteins (antigens and antibodies) and their reaction in different animals show phylogenetic relationship; antibody antigen reaction in an immunological reaction leading to precipitate formation when blood sera of of different organisms are mixed shows common ancestry√ . The greater the amount of precipitate formation in two different animals the closer the phylogenetic relationship; (vii) Geographical distribution Initially, the earth was one landmass pangea Due to plate tectonic forces it splited into present day continents; (continental drift). Before the split areas had similar climates√ after split, members of some spheres became isolated √ by barriers complied different climatic regions evolved inadequately adapting√ in the areas isolated landmasses led to evolution of new forms √ of organisms quite distinct from those found in other areas. (viii) Taxonomy Modern classification of organisms id based on the similarities and differences that exists between various natural characteristics. Organisms in some taxonomic unit share similar characteristics indicating or showing a common ancestry or origin√. (35 ticks, maximum 20mks) (a) (i) The auxins are positively geotropic √ diffuse to the lower region of the root tip. High auxin concentration inhibits √ growth in roots thus lower region of root grows slowly; then upper part, thus curvature downwards √. (3mks) (ii) Auxins are positively geotropic, diffuse to lower region of the shoot tip high auxin concentration stimulates growth in shoot, lower region with high auxin grows faster, than upper part, thus curvature upwards √. (3mks) (b) Looking at the sunlight jet Circular muscles in the iris contract; while the radial muscles in the iris relax The pupil becomes small; Less light passes through the pupil to get into the eye; Ciliary muscles in the ciliary bodies relax; Suspensary ligments become stot/tension increases in the suspensory ligaments; The lens becomes long and thin; The jet is brought to focus Looking back at a page Circular muscles in the iris relax while radial muscles contact; The pupil becomes large; More light passes through the pupil to get into the eye Ciliary muscles in the ciliary bodies contract Suspensory ligments loosen/tension is reduced or lost in the suspensory ligaments; the lens becomes short and thick; The printed words in the page are brought to focus Maximum 14mks S – cale C-urve A – xes P-lotting Total ©Muhoroni District Form Four 2014 (14mks) 23 marks, maximum - 20mks) 02 mks; Horizontal and vertical scale workable, consistent 1mk each 01mk; Be smooth and continuous. 01 mk; x –axis, temperature be in 0C (½ mk) y-axis, rate of reaction (½ mk) 02 mks; All points be well plotted. (06mks) 4 Biology Paper 2