Download kaloleni-rabai district joint mock exam

KALOLENI-RABAI DISTRICT JOINT MOCK EXAM
231/2
BIOLOGY THEORY
PAPER 2
01/08/2013
2 HOURS
Marking scheme
1.
a)(i)
Man = XbY
Bb
Woman X X ;
(ii)
P. Phenotype
colour blind man
x
B
P. Genotype
P. gametes
B b
XY
X
b
Y
x
x
XX;
B
b
X
X√
Cross
F1 generation
2.
carrier woman
;
Bb
bb
XX
XX
B
b
XY
XY;
(b) (i) ¼ ;
(ii) ¼ ;
(c) Males have a single ‘X’ chromosome which makes it 50% chance for the occurrence of colour
blindness i.e. requires only one gene Y; Y chromosome does not associate with sex linked
disorders; No carrier males;
(a) (i) Non – living components/ physical factors in an ecosystem;
(1mk)
(ii) Living components in an ecosystem;
(1mk)
(b) A – Arid/semi arid/dry land;
(3mks)
B – Forest/well watered soil;
C – Aquatic/fresh water;
(c) Sunken; hairy; reversal/rhythm; small stomatal/pores/apertures (3marks_
3.
X
Y
– Vacuole / Sap vacuole
– Tonoplast;
Z
– Chloroplast;
(3marks)
(a)Cellulose
(1mark)
(b)Active transport
(1mark)
The cell sap is hypertonic to the solution / distilled water; hence water molecules move into the
cell; by osmosis; making it to swell and eventually burst;
(3ma2.
(a) X – Phalanges ;
Y – Humerus;
Z – Carpals;
4. (b)
(i) Homologous structures;
(ii) Adaptive radiation/divergent evolution;
(iii) Enables organisms to exploit different ecological niche and avoid competition;
(c) He argued that characteristics acquired by an organism during its life would be passed on to the
offspring; it’s was later proved that only characteristics in ones genes were inherited; (2marks)
5.
(a)
(2mks)
(b)
(c)
(i)
A;
(1 mark)
(ii)
Exhaled air has more carbon (iv) dioxide; (than B);
- Poisonous if it accumulates;
- Muscle clump;
1 mark)
(d)
(e)
(e)
Respiration
- Fatigue
Mark any two correct
Cardiac muscles;
(1 mark)
- Kill microorganisms (lactobacillus) bacteria R; germs;
- High temperature derative bacteria enzymes / stops anaerobic respiration; R;
alone or aerobic respiration; Rj germs
A-Intermittent /Discountinous growth;
6a)
(1 mark)
B- Continous growth;
b) Rigid/hard exoskeleton; prevents growth; the exoskeleton is shed during moulting; this
allows
rapid growth ;to occur before the new exoskeleton hardens up;(4mks)
c)
Ecdysone/ moulting hormone;
(1mk)
(d) i) P&Q
Slow rate of growth, due to small number of cells dividing; the young organism is still b
adapting
to new environment;
iii) Q & R
e)
-
Rapid/ fast rate of growth; due to large number of dividing cells;
-
The organisms has adapted to the environment;
-
No limiting factors like space, wastes e.t.c.;
(4mks)
i) Internal fertilization;
ii) Provide protection to the developing embryo from harsh environment;
Less number of gametes are involved./ No waste of gametes;
Developing embryo experiences little environmental changes; (2mks)(Any two)
f) i) Meiosis;
ii) Crossing over;
(1mk)
Synapsis/ formation of bivalents;
(2mks)
7.
- Just after menstruation, the pituitary gland secrets follicle stimulating hormone (FSH) √; which
is carried by blood to the ovary; √
- FSH stimulates the development of graafian follicles; √
- It also stimulates the follicles within the ovary to secrete oestrogen hormone √which is
carried by
blood throughout the body; √
- Oestrogen stimulates the development of secondary female characteristics; √and initiates
healing
and repair of uterine wall (endometrium) following menstruction; √
- As oestrogen levels rise, a negative feedback message is sent to the pituitary gland to turn
secretion of follicle stimulating hormone; √
- Simultaneously the rise in oestrogen levels stimulates the pituitary gland to secrete lutenising
hormone, √ which is carried by blood;
- Lutenising hormone (LH) causes ovulation√
-
8.
b)
LH also stimulates the graafian follicles to form a functional corpus luteum; √
It also stimulates cells of corpus luteum to secrete oestrogen and progesterone; √
The build up of progesterone (and oestrogen) will stimulate the proliferation √ (thickening)
of the endometrium in readiness for implantation; √ should fertilization occur;
- The build up of oestrogen and progesterone levels activate the second negative feedback; √
by inhibiting the secretion of the FSH and LH by the pituitary gland; √
- Without gonadotropins (FSH and LH); √ the corpus luteum begins to deteriorate, slowing
oestrogen and progesterone production; √
- The drop in ovarian hormones (oestrogen and progesterone) signals the beginning of
menstruation; In this case the endometrium, denied hormonal support will slough off to be
released as menstrual fluid (blood & tissue debris); √
- Another cycle soon begins; √
Total 25mks
Max 20mks
(a)
Describe the characteristics and functions of the three types of muscles found in the
mammalian body. (1 lmks)
Skeletal muscles or striated muscles
Attached on the skeleton.
Have strips running across them thus called striped or striated
Made up of a bundle of long fibres running the length of the
Are multinucleated.
The covering of a muscle fibre is called sarcolemma.
The functional unit of the muscle is the myofibril.
The muscle is innervated by the voluntary part of the nervous system
Have numerous mitondria.
ii)
Smooth muscles of visceral muscles
Found on the walls of tubular visceral organs.
Cells are spindle shaped with a single nucleus.
Lack striations
Innervated by the autonomic part of nervous system (are involuntary)
iii)
Cardiac Muscles
Each muscles fibres consists of short cells with centrally placed
nuclei and numerous striated fibrils.
Ends of cells marked by interacalated discs
Are myogenic and independent of nervous stimulations
Capable of continuous contraction without fatigue.
Explain how the various components of blood are adapted to perform their functions. (9mks)
i)
Plasma
90% water in which substances are suspended or dissolved.
ii)
take
infected
Contain glucose, mineral salts, hormones, some enzymes, amino acids and lipids; plasma
proteins.
Red blood cells
Have no nucleus to increase room for package of haemoglobin . (This enables it
carry more oxygen.)
Haemoglobin is a protein; which containes iron and readily combines with
oxygen to form oxyhaemoglobin /Haemoglobin has high affinity for oxygen
Are numerous of facilitate oxygen / CO2 / gases transport
Due to their biconcave shape are capable of squeezing through the capillaries
The biconcave shape increase surface area overwhich gaseous exchange can
place.
White blood cells. (Leucoytes)
Number increase with increase in infections
Granulocytes have lobed nuclei and granulated cytoplasm.
Use amoeboid movement to pass through the walls of the capillaries into
area.
A granulocytes lack granules in their cytoplasm
Produce antibodies which are antitoxins to neutralize the toxins.
Platelets (Thrombocytes)
Fragments of red large cells.
Prevent excessive bleeding through clotting and formation of fibrin, a meshwork
of fibres.
4.