BIOLOGY PAPER 1 Marking Scheme - 2017 KITUI MOCK EXAMINATION

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BIOLOGY PAPER 2 - 2017 KITUI MOCK EXAMINATION

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Living organisms unlike motor vehicles, show the following characteristics; reproduction, growth and development, irritability / sensitivity, respiration, gaseous exchange and nutrition. Any 3 points (3 marks)
1. Sucking small insects/small animals from rock surfaces and bark of trees. (1 mark)
2. Attracting and trapping small crawling animals. (1 mark)
1. Site for protein synthesis; (1 mark)
2. Contains lytic enzymes that destroy the worn our cells / organelles / entire cell. (1 mark)
1. Moves the body tube through smaller distances to bring image into sharp focus; (1 mark)
2. Is the platform where specimen on the slide is placed; (1 mark)
to enable easy manipulation or positioning of specimens as wetness causes the slide with the specimens to stick onto the stage; (1 mark)

1. The visking tubing will become swollen / bigger / enlarged / increase in size / turgid; (1 mark)
2. Sucrose solution is hypertonic compared to the water in the beaker (or water is hypotonic compared to sucrose in the beaker); water moves from the beaker into visking tubing by osmosis through semi-permeable visking tubing; making the visking tubing to swell or to increase in size; (3 marks)

Diffusion	Active Transport
Molecules move from a highly concentrated region to a lowly concentrated region	Molecules move from a lowly concentrated region to a high concentrated region
Movement of the molecules is along a concentration gradient	Movement of molecules is against the concentration gradient
No energy is required	Energy is required
Does not require protein carrier molecules	Requires protein carrier molecules

Any 2 marks

1. - Absorption of water from the soil by root hair cells;
  - Opening and closing of the stomata;
  - Support in herbaceous plant due to the turgidity of the cells;
  - Feeding in insectivorous plants; Mark first one point
2. - Water reabsorption by blood capillaries from renal lubules / absorption of water in colon or gut;
  - Movement of water from cell to cell in animals; Mark first one point

Nitrogen; Magnesium; iron Mark first two points

1. To increase the respiratory enzymes hence increasing the rate of respiration. (1 mark)
2. 1. Stroma; (1 mark)
  2. - Bearing photosynthetic pigments or chlorophyll molecules hence site for light dependent reaction where light is trapped for photolysis;
    - It provides a large surface area for maximum chlorophyll hence photolysis; (Any 1 mark)

Hydrogen ions; Oxygen gas; ATP (Any 2 marks)
1. They activate the enzymes (1 mark)
2. Iron (Fe²⁺); magnesium (Mg²⁺); Zinc (Zn²⁺); Copper (Cu²⁺); Calcium (Ca²⁺) (Mark first one point)
In the stomach there is acidic medium due to presence of hydrochloric acid (HCl) and ptyalin only acts at slightly alkaline medium hence it is denatured or destroyed by a low pH; (1 mark)
- Source of energy when oxidized;
- Act as storage materials;
- For structural compounds; Mark first two points

1. Xylem; (1 mark)
2. Phloem tissues; (1 mark)
3. Apical meristems; (1 mark)
1. Cohesion force enables the water molecules to stick together in a continuous column in the vessels since water molecules attract one another; (1 mark)
2. Adhesion force enable water molecules to stick or get attracted to the vessel walls hence water rises up the vessels; (1 mark)
1. Open circulatory systems; (1 mark
2. 1. Hepatic portal vein; (1 mark)
  2. Pulmonary vein; (1 mark)
1. - Thrombosis (Coronary thrombosis)
  - Varicose veins;
  - Hypertension;
  - Arteriosclerosis; Mark first one point
2. - Have biconcave in shape to increase the surface area for packaging of more haemoglobin hence absorption of gases;
  - Absence of nucleus to increase surface area for packaging of haemoglobin;
  - Presence of red pigment (haemoglobin) that has high affinity for oxygen;
  - Ability to change their shape thus can squeeze through narrow capillaries Mark first two points NOTE: Feature must be followed by a reason

Carboxyhaemoglobin is a very stable compound that does not easily dissociate; therefore reduces the capacity of haemoglobin to transport oxygen to the tissues; (2 marks)
- Thin wall / thin epithelium for faster diffusion of the respiratory gases / reduces the diffusion distance for diffusing molecules;
- Always moist for respiratory gases to dissolve and diffuse in solution form;
- Large surface area for maximum diffusion / gaseous exchange;
- Highly vascularized to maintain a steep concentration gradient; (4 marks) NB: Feature must be accompanied by reason

1. Bordetella pertussis; (1 mark)
2. Streptococcus pneumoniae (1 mark)

- Ethanol / Ethel / Ethanoic acid / Alcohol;
- Carbon (IV) oxide;
- Energy (ATP); (3 marks)

- Body size;
- Sex;
- Age;
- Basal metabolism rate;
- Activities / every day’s activities; Mark first two points

Muscles respire anaerobically; resulting in accumulation of lactic acid in the tissue, causing fatigue/muscle crumps/pain. Since lactic acid is toxic, it must be broken down into carbon (IV) oxide and energy; therefore extra oxygen must be taken in to oxidise lactic acid; (2 marks)
1. Diabetes insipidus; (1 mark)
2. Antidiuretic hormone (ADH); (1 mark)
- Cools the body when latent heat of vaporization is carried away;
- Gets rid of waster / materials of excretion e.g urea, sodium chloride, uric acid, lactic acid;
- Contains antiseptic properties therefore kills the micro-organisms in the skin; Any 2 marks

- The amino acids are broken down into amino group (NH₂) and carboxyl group (COOH), a process referred to as deamination;
- The amino group combines with hydrogen forming highly toxic ammonia; which immediately goes into ornithine cycle where it combines with carbon (IV) oxide
- forming urea that is less toxic that is removed by the kidneys; the carboxyl group is converted to glucose / carbohydrates and then oxidized to yield energy or is converted into neutral fats and deposited in adipose tissue; (3 marks)

- Some waste products are stored in non-toxic form in leaves, flowers, fruits and old bark which age and drop off;
- Some waste products such as oxygen are reused or recycled;
- Some waste products are formed slowly thus little accumulation of wastes;
- Some wastes e.g gases easily diffuse out of the plant tissues;
- Some waster products are mainly made from carbohydrate and hence are not as harmful as proteinous materials;
- Plants are less active; (4 marks)

Chilopoda	Dipolopoda
A pair of walking legs per segment	2 pairs of walking legs per segment
Body flattened dorsoventrally	Body cylindriocal in shape
Body divided into head and trunk (2 body parts)	Body divided into head thorax and trunk (3 body parts)
Have a long antennae	Have short antennae
Have poisonous claws	Lack poisonous claws
Posterior geniotal aperture	Anterior genital arpeture

1. - Numerous chloroplasts that are highly sensitive to trap light of low intensity;
  - Deeply dissected leaves into straws to increase surface area hence trap more light and more gases;
  - Large air spaces for storage of air hence buoyancy and parenchyma tissue for storage of air;
  - Have no cuticle to facilitate exchange of gases rapidly; Any 2 marks
2. - Albinism;
  - Sickle cell anaemia;
  - Haemophilia;
  - Colour blindness Mark first two points

Rods	Cones
Perceives light of low intensity	perceive light of high intensity
Not sensitive to color	sensitive to color
Have low visual acuity since they have retinal convergence	Have high visual acuity since they lack retinal convergence

Mark first two points

- Supports or protects the delicate inner parts against mechanical injury or infections;
- Prevents drying out of organism / desiccation since it is waterproof;
- Provides surface for attachment of the muscles; Mark first one point

BIOLOGY PAPER 1 Marking Scheme - 2017 KITUI MOCK EXAMINATION

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