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Bomet biology PPR2 Answers

BOMET COUNTY JOINT EXAMINATIONS – 2015

231/2 BIOLOGY PAPER 2

MARKING SCHEME

  1. a) Genetic diseases can be easily eliminated; Gene exchange /mixing leads to hybrid vigour;

b) Heterostyly; protogyny; protandry; incompatibility of alleles;

c) i) Production of spermatozoa;

ii) Provides passage for the ovum to the uterus after fertilization; fertilization takes place in the upper region of the oviduct;

iii) Produces an alkaline fluid that neutralizes acid in the vaginal/urethra (male); the fluid contains nutrients for the sperm; and also activate sperms; ( mark 1st point)

  • a) i) Kingdom protoctista;Acc.protista

Reason: Unicellular; eukaryotic, reproduce by a sexual fission;

ii) Structure labeled A

Cilia;

iii) Part C function

To get rid of excess water by osmosis;

b) i. Red blood cells; rej singular red blood cell

ii. Oxygen;

iii.Formed from part of blood minus blood cells and plasma that ultra filtrates to fill in channels and spaces between the cells;

iv.Leucocyte; Acc-White blood cell/Phagocyte

  • a. Female have two x chromosomes in a gamete while males have only one x chromosomes

the gene for hemophilia is located on the x –chromosomes ,such that in heterozygous condition a female does not show the trait

b) H- Normal gene

h-Gene for hemophilia

Parental phenotype: carrier x normal;

Parental genotype: XHXh   X   XHY;

XH
Xh
XH
Y
XHXH                XHY       XHXh                     XhYhHHJhhhhhhhhhfffffg
; ;

Gametes

Children: XHXH:,XHY:,XHXh:,XhY;

c) Colour blindness;

d) Vertebrates embryos have similar morphological features; with suggest a common ancestry;      (2mks)

Accept: 3 classes or 3 examples of vertebrates and specify any two features e.g. single circulatory system ;( segmented) myotomes notochord; gills; pharyngeal; cleft; tail;

  • a) M increase; less N formed, therefore less p;

b) Peptidase;

c) i) More N is formed;   (1mk)

ii) N accumulates, no P is formed;3

d) Temperature

PH value rej; Ph, PH

 Concentration of substances;

Enzymes and product;

  • a.i) parts labeled N,P,U and V

N-Plumule ;

P-Radicle ;

U- Hypocotyl ;

V- Epicotyl;

ii) Functions of

M- Store food for the seedlings;

T- Allows entry of water and oxygen;

b)  State type of germination exhibited by a garden pea

Hypogeal germination;

c)  In garden pea; cotyledons remain underground while broad bean; cotyledons are thrust above the ground; (mark as a whole// score 0 or 1mk)

  • a. On the graph paper

b) 80-18/2.5 = ; =2.480c/min;

c) Control;

d) Rate was faster in tube A because the film of methylated spirit evaporated; removing heat from the tube;

e) Convection;

Radiation; 

  1. lower rate of heat loss;
  2. i.Birds

feathers

ii.Mammals

fur;

  • i.Skin;

ii.Hypothalamus;

  • a) Distinguish between tissue respiration and breathing

Breathing is inhalation of oxygen rich air and exhalation of air rich in carbon (Iv) oxide

Respiration is chemical breakdown of food in body cells, to release energy

b) Describe how carbon dioxide produced by respiratory liver cells reaches alveoli cavities in the mammalian lungs

From the liver cells the carbon (IV) oxides diffuses into the surrounding blood capillaries;

  • Once in blood most carbon(iv) oxide dissolves in the red blood cells cytoplasm to form weak carbonic acid  while some dissolves in the plasma to form carbonic; acid and the rest combines with hemoglobin; to form carbon carbaminohaemoglobin;
  • It is transported in these forms in blood from the blood capillaries; to the hepatic venules which unite to form the hepatic vein;
  • From the hepatic vein the carbon(iv) oxide in blood is transported to the inferior venacava; then to the right atrium;
  • The right atrium drains into the right ventricle; via the bicuspid valves;
  • The right ventricle then contracts; forcing the blood with the carbon(iv) oxide into the pulmonary artery; via the pulmonary semi-lunar valves;
  • The pulmonary artery branches into pulmonary arterioles; then into capillaries and alveoli; into the capillaries in the lungs; then to the alveoli capillaries;

The carbon (iv) oxide then diffuse past the thin epithelia of blood capillaries and alveoli; into the alveoli cavity; from where it is exhaled into the environment; (20 points maximum 16 marks)

8. a)Describe the roles of the following hormones in growth and development of plants

Auxins /indole acetic acid;

  • Promotes cell division ;
  • Influences tropic responses;
  • Promotes formation of abscission layers;
  • Promotes fruit formation ;
  • Promotes cell differentiation;
  • Causes apical dominance/inhibits growth and development of lateral buds ;
  • IAA with cytokinins induce formation of callus tissues;
  • Promote growth of adventitious roots;

Ethylene

  • Stimulate lateral bud development;
  • Ripening of bananas /fruits ;
  • Induces thickening of stem/inhibits stem elongation;
  • Promotes germination of certain seeds ;
  • Causes abscission of leaves/fruits/leaf fall;   mark 1st 10 points (10mks)

b.Leaves covered with thick/waxy cuticle; that is water proof /impermeable; to water; allowing for reduced rate of transpiration;

  • sunken stomata; water vapour accumulate is the pits; reducing the rate of transpiration
  • have few or no stomata on the upper surface of the leaf/more stomata or can lower surface sheltered from direct sunlight; the fewer the stomata the less the water loss from the plant
  • Some plants have small stomata/small stomata/ pore; thus reducing transpiration  rate
  • Plants with small/needle-like leaves/spines; expose less surface area; hence reduce the rate of transpiration
  • Leaves with shinny surface; reflects light resulting is reduced leaf temperatures; thus reducing the rate of  transpiration
  • Some plants have  leaves covered with hairs/scales; which trap a layer of moisture; reducing the rate of transpiration;.