MANGA SUB-COUNTY
231/2
BIOLOGY
Paper 2
July/August- 2015
MARKING SCHEME
1
a)
3:1
b)
i)
Genotype
b)
(ii)
Genotypic ratio:Rr:rr
1:1
Phenotypic ratio:Red:white
1:1
2
c)
Alternate form of a gene in a pair that determine a characteristic;
a)
Soda - lime /sodium hydroxide ; To absorbs the carbon (IV) oxides produced:
b)
To maintain an almost constant temperature during the period of the experiment ; a small
rise in temperature causes air to expand ; a small fall in temperature causes air to contract
leading to erroneous results;
(3mks)
c) The level if water in the capillary would rise;
(lmk)
d) The insert respired taking up oxygen ; releasing carbon (IV) oxide ( which is absorbed
by soda lime), up take of oxygen caused a decrease in air pressure within the flask;(3mks)
e) A control can be set up by substitution a living insert with a dead one;
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3
4
(a)
(b)
Second / Third
(lmk)
(c)
Sea grass
(d)
The population of molluscs / insect larvae would increase; due to decreased
insect
small
Eagle
Larvae
Fish
predation;
(2 marks)
(e)
Shows the actual amount of energy flow of a food chain;
(1mark)
a)
Is the study of the functions of cell structures / the process in which cells work (lmk)
b)
i)
Osmosis
ii)
Hypertonic / more concentrated solution
iii)
Inner cells / Cut surface absorbed water fast’ by Osmosis become swollen /
(lmk)
turgid faster than the outer epidermis cell the inner cells enlogate hence curving
outwards.
(3mks)
c) Water logging prevents aeration of the soil hence less oxygen slowing down
respiration
in root hairs leading to less energy released for active transport necessary for the
absorption of mineral ions, salts. Max of
a)
Max of (2mks)
H-Eustachian tube;
J-Semi-circular canals;
b)
H-Tubular/hollow with air to equalizes pressure between the outer and the inner ear;
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M-Funnel shaped to collect sound waves;
N-contains perilymph endolyph which transmits waves to structure K;
6
c)
Deafhess;
d)
Endolymph
e)
Body balance/posture;
a)
i)
Plasma proteins molecules too large ; to pass through the capillary walls of the
glomerula hence left in blood;
ii)
Glucose and amino acids selectively reasbsorbed; along the kidney tubules
completely
b)
c)
i)
Nitrogenous wastes, mineral salts and water; any two.
ii)
Osmoregulation , / conservation of glucose and amino acids; any one.
i)
High pressure;
ii)
Blood reaching the renal artery being at high pressure due to pumping of
heart; narrow glomerular capillaries cause pressure build up due to blood
flow; / afferent renal artery has a wider lumen ; than the efferent renal
artery lumen. Rej if c (i) is wrong.
d)
Excess amino acids are deaminated in the liver to form urea ; Amino acids break into a
nitrogen component and carboxyl group; The amino group combine with carbon IV Oxide
to form urea;
e)
i)
C:
Ammonia is very toxic and require a lot of water to dilute hence the mammal releasing a
lot of dilute urine;
ii)
D;
Shortage of water in Desert, mammal excrete little amount of urine to conserve water;
iii)
Long loop of henle in D than in A / shorter loop of henle in A than in D; more
glomerular in A than in D;
iv)
ADH make the walls of the tubule permeable to water resulting to little amount of
concentrated urine; (The reverse is true)
7
-
Cerebrum ; controls learning ittellingence , reasoning ; thought ; memory ; speech; hearing
;smell; taste;
-
Hypothalamus ; controls body temperature ; ability to sleep and wake up ; appetite;
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osmoregulation ; secrection of hormones;
-
Pituitary gland ; secretes hormones likes ADH / F.S.H / L.H/ Prolactine! ‘O xytocin;
-
Thalamus ; integrates sensory impulses eyes ; ear; skin and sends them to cerebrum; Of
factory of likes ; controls sense of smell;
-
Ventricles contains cerebral spinal fluid which supplies nutrients and oxygen ; to brain
tissues; removes metabolic wastes for brain tissues ; acts as a shrink absorbs;
-
Optical lobes ; control movement of the eye;
-
Cerebellum ; controls body balance / movement! posture;
-
Medulla oblongate : controls involuntary movement sneezing/ vomiting / blood circulation
/ breathing;
8
-
Vetricles / meninges ;‘ protection against mechanical damage.
-
Arachnoida layer; setuctes cerebral spinal fluid;
Comparative anatomy;
Comparisons of structures of different organism show resemblances in structure; and functions; e
.g Digestive systems; Homologous structures ; like pentadactyly limb; invertebrates are similar
but perform different functions; showing common ancestry; analogous structures; are
morphologically different but perform similar functions; showing convergent in Evolution;
Comparative embryology;
Embryos of vertebrates have great similarity showing common ancestry; e.g the long thin and
other body system;
Cell biology ; Compartive serology;
Cells from different organism have similarity in structure; and functioning ; closely related
animals have similar plasma proteins; suggesting common origin;
Geographical distribution;
Organisms originated from a common dispersal centre; when the continents were joind;
continental drift occurred isolating the organisms bring different patterns of evolution due to
adaptations ; e.g the gala pages finches
Taxonomy;
Classification based on Evolution relationship show great similarity in organism of the same
Taxa; e.g phylum having less common features while species have the highest common features.
(Max 20 mks)
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