Zoology Solved Past Paper 2nd year 2015 Karachi Board

solved MCQs Pass Papar 2015 Zoology

solved MCQs Pass Papar 2015 Zoology

solved MCQs Pass Papar 2015 Zoology

solved MCQs Pass Papar 2015 Zoology

SECTION ‘B’ (SHORT – ANSWER QUESTIONS)

2.i) Write about the different types of Neurons.
Neurons: “Neurons are the structural and functional unit of nervous system. They are exitable ceUs of which nervous tissue is made.”
TYPES OF NEURON: Neurons are classified on following bases.
1- Structural basis.
2- Number of cell processes basis.
3- Physiological basis.

1-STRUCTURAl BASIS
i) Myelinated Neuron: A fatty cell i.e. the Schwann cell repeatedly wind around axon of a nerve cell and makes it insulation, so anow rapid flow of electrical imp Ise through it.
ii) Non Myelinated Neuron: They do not-have myeline sheath around them.

2-NUMBER OF CELL PROCESSES BASIS:
i) Unipolar Neuron: In this type, onry one cell processes (axon) arises from soma. Some times this cell processes (axon) divides into two then called as pseudounipolar neurons.
Location: They are found in mesencephalic nucleus and post root ganglia
ii) Bipolar Neuron: In this type Axon and dendrites arise from opposite poles of soma.
Location: They are found in retinal bipolar cells and spinal and vertibular ganglia.
ii) Multipolar Neurons: In this type Axon arises from one pole of soma and dendrites arises from several poles of soma.
Location: They are found in central nervous system i.e. Brain. and
spinal cord.
3 – PHYSIOLOGICAL BASIS: There are three types of neurons,
1-Sensory Neuron: It receives information from receptor cell and transmit it to central nervous system (CNS) i.e. (Brain & Spinal cord).
2-lntemeuron: It is interposted between sensory and motor neuron.
3-Motor Neuron: It transmit impulses i.e. messages from central nervous system (CNS) to effector organs.
Receptor cell
Sensory neuron
CNS

ii) Write a note on Uthotripsy or Acid Rain.
Uthotripsy: Lithotripsy is used for non surgical removal of kidney stone. It is the technique used to break up the stones that form in the kidney, ureter or gall bladder. There are several ways to do it, although U1e most common is extra corporeal shock wave (ECSW) lithotripsy. High concentrations of X-ray or ultrasound are directed from a machine outside the body to the stone inside. The shock waves break the stone in tiny pieces or into sand, which are passed out of the body in urine.
Acid Rain: Many industries produces harmful gases like S02, C~ and N02 in air. These gases reacts with moisture in air or In rain water, which comes to earth with rain and causes to increases acidity of land water which harm animal lives in sea water and plant live in irrigating water. This acid rain can directly harm human beings and man made structure e.g statues of archaeogical importance. This whole process is called acid rain.

iii) Describe Osmoregulation in Terresterial animals.
Osmoregulation is important mechanism in all groups of animals. The terrestrial animals have developed number of strategies to maintain osmoregulation of their body.fluid, like,
a- Water Proof Exterrral Coverings: To prevent water loss through
external surfaces, vertebrate like reptiles, birds and mammals have water proof keratinized epidermis. Similarly, the insects have developed an external water-proof layer called cuticle.
b- Storing and Excretion of Solid Wastes: Reptiles, birds and insects excrete uric acid as nitrogenous waste, which is insoluble in water. It is stored temporarily in cloaca where water is reabsorbed from it before its removal from the body in semi-fluid form.
c- Use of Metabolic Water: Some mammals like camel, kangaroo, rat etc. make use of water produced during the break down of body fats.
d- Storing the Wastes: Mammals do retain some urea in their kidneys where reabsorption of water occurs

iv) Define Renewable and Non-renewable resources and give examples.

Renewable and Non-renewable resources

Renewable and Non-renewable resources

v) Write the basic steps of Recombinant DNA technology.
Recombinant DNA contain DNA from two different sources. The basic step in the recombinant rDNA technology or genetic engineering are as under.
1- Prepartion of recombinant (rDNA) molecule.
2- Insertion of rDNA into host cell.
3- Multiplication and production of numerous copies of host with rDNA.
1-Preparation of Recombinant rDNA (rDNA) Molecule: Recombinant DNA molecule contains DNA from two different sources. Preparation of rDNA required vector (plasmid, bacteriophage), restriction enzyme (molecular scissors) and DNA ligase enzyme.
a) Vector: It is a DNA molecule into which a gene is inserted. It is capable of replication in host. It acts as a vehicle to transport rDNA.
Example: Bacterial plasmid and bacteriophage virus.
b) Restriction Enzyme: It is another tool for rDNA and consist of group of enzymes, which are required to cut a source DNA molecule into small pieces and to cut plasmid, make a gap where foreign gene has to be filled in it. These are naturally found in bacteria for protection against viruses. They are called restriction enzyme as they restrict growth of virus. These are first discovered in 1960. The cut end of DNA has specified sites called sticky ends. These sticky points are used in laboratory to join DNA pieces-.
c) DNA Lygase Enzyme: The third tool in rDNA technology is DNA
Iygase enzyme. These enzyme seal the cut fragments with sticky ends of vector. .
2-lnsertion of rDNA into Host Cell: In r-DNA technology, usually a host is a bacterial cell. The bacterial cells take up r-DNA when they are treated with calcium chlroride to make them more permeable.
3-Multipication of Host With rDNA: When host cell divides and redivide, the copies of rDNA molecules are passed to progency” and further replication of vector i.e. plasmid take-place, After a large number of cell division a clone of identical host cell is produced. Each cell in clone contains one or more copies of rDNA molecule.

Thus the gene carried by this rDNA is said to be cloned.
4-Selection of Bacteria or Gene of Interest: There are three possible
ways to get a gene of interest. .
1- To isolate-it from chromosome.
2- To chemically synthesize it.
3- To make it from m-RNA.

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vi) Explain Hardy Weinberg Law.
In 1908, G.H. Hardy, English mathematician and W.Weinberg, German phycician gave relationship between frequencies of alleles and genotypes in popultaion. According to them,
“The frequencies of dominant and recessive allels in a population will remain constant (unchanged) from generation to generation provided certain conditions exist.”
They gave an equation, which is an expression of binomial expressions (p+q)”, where “p” is the frequency of one allele and “q” is the frequency of another allele. Yeild the formula of Hardy-Weinber equation,

formula

formula

If the genetic equilibruim found in a popplation (as in above example) then the deme of population remains unchanged. Evolution can only takes place when genetic equilibrium is upset.

Question Answer

Question Answer

These highly variable and virtually unique lengths of non-functional DNA are passed on to the offspring alongwith the compliments of genes in a Mendelian fashion. Since RFLPs of each human are unique analogous to the fingerprints, which are used as marks of identity, so RFLPs can be termed as DNA fingerprints .
xi) Name the marked parts of the following diagram

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a- An oily liquid called synovial fluid helps the joint move smoothly
b- The synovial membrane around the joint stops the synovial fluid from draining away.
c- The bones at a joint are held together by strong fibres called ligaments.
d- Where the bones rub together they are covered by a slippery layer of cartilage. .

xii) Write four differences between Diffused and Centralized nervous system.

differences between Diffused and Centralized

differences between Diffused and Centralized

xiii) Write a note on Oestrous cycie.
The mature egg under effect of hormonal secretion in female initiate certain behavioural changes that indicate their readiness for mating and animal is said to be in heat. In heat means the period of sexual receptivity. The process occurs in cyclic manner, so it is called as “oestrous cycle”. It occurs only once a year in mammal while in some cases it occurs more often, This cycle ensures that Ova is mature and ready for fertilization. This cycle never occur in human being.

xiv) Explain the role of Brain in the regulation of body temperature.
The body temperature regulation in humans is based on complex homeostatic systems facilitated by feedback mechanisms. The homeostatic thermostat is present in the-hypothalamus, a brain part. It responds to the changes in the temperature above and below a set point which is 37°C.

In case of increase in temperature above the set point, certain warm
temperature sensitive thermoreceptors in skin, hypothalamus and other parts of nervous systems send the signals to the system that increase the blood flow to the skin and also cause sweat gland activation and the sweat is evaporated for the cooling.

In cold temperature, the cold receptors send the impulses to hypothalamus to inhibit heat loss mechanisms and activate the heat conservation mechanisms. This includes constriction of superficial blood vessels and stimulating shivering mechanisms.

xv) What is the function of Pelvic girdle? Name its three important bones.
The pelvic girdles serve to attach the legs with the vertebral column at the hip region. Each pelvic girdle called innominate bone is formed by the fusion of three bones (i) Ilium, (ii) Ischium, (iii) Pubis. The bones of leg include a femur, in the thigh, connecting the leg with pelvic girdle by a ball and socket joint, two long parallel bones the tibia and fibula in the shank with a small patella bone at the knee joint. There are present 7 small tarsal bones in the ankle, 5 long slender bones in the sole metatarsal and 14 bones the phalanges arranged in five rows one row in each of the five toes.

xvi) Describe the functions of Encapsulated receptors of the Skin.
The nerve endings of these receptors are enclosed in capsule of connective tissues. Following capsulated receptors lie in the skin. Meissner’s Corpuscle: Abundant in hair-less areas of skin such as finger tips, lips, eye-lids, nipples, palms, soles etc, these are sensitive to touch. Their capsules consist of thick collagen fibers with spiral and highly coiled nerve ending.
Pacini an Corpuscle: In this corpuscle, the sensory nerve ending is
surrounded in concentric, onion-like layers of membranes  lternating
with fluid filled spaces. These are located in dermis as well as in some intemal organs and freely moveable joints. Pacinian corpuscles respond to rapid change ill pressure associated with touch and vibrations.

SECTION ‘C’ (DETAILED – ANSWER QUESTIONS)

3. Define Menstrual cycle. Describe its various phases and the changes occurring in each phase.
The monthly maturation of egg and uterine preparation are collectively called Menstrual cycle. Mestrual cycle is the preparation of uterus for posible pregnancy. It is controlled by harmones and completes by every 28-days. It divides grossly into two halves of cycle.
A – Proliferation phase
i) Mensturation or M-phases
ii) Follicle or F-phase
B – Secretory phase
i) Ovuiation or O-phase
ii) Corpus Luteum or L-phase (if fertilization occurs)

A· PROLIFERATION PHASE:
i) Menstruation or M-Phase:” rAersstruation is a secondary sexual character of females occuring at puberty. Menstruation is cyclic shedding of endometrium with passage of blood from broken down capilleries in sponqy and compact layer of endometrium, unfertilized ovum and secretions from ge P,t~1’rac. It starts at age of 12-14 year, continues thro g child beanng tlge stops usually at age of 45-50 years.
Endometrial Changes: The endometrium respons to ovarian hormones. The endometrial cycle is divided into, Follicle phase and Ovulation phase.
ii) Follicle Phase or F-Phase: This is of variable duration (14±7 days). It starts on first day of menstruation. This phase corresponds to ovarian cycle (proliferative phase) during wbich oestrogen produces frqm granulose cells of ovarian follicles under influence of FSH from anterior pituitary. This phase consist of following.

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a- Menstruation: Menstruation last for 2-8 days. Withdraw! of hormones (from ovary and endometrium) causing shedding of superficial (compact) and intermediate (Spongy) layer of endometruim. The blood loss in menstruation is about 5-80 ml (ave- 30 ml).

b- Reparative stage: The repair of endometrium starts during menstruation. The blood vessel and glands in the Basal layers start to proliferate. This proliferation occur under influence of hormone OESTROGEN. The endometim become thicker 3-4 mm (from 1-2mm) but the secretory activity is not started in this phase.
B- SECRETORY PHASE: This phase is of constant duration i.e, 14 days. The proliferative activity is continuous but the secretory activity is more dominent.
This phase consists of following .
i) Ovulation or 0 phase: The release bf ovum from ovary at 14th day of Menstrual cycle (Endometrial cycle) is called ovulation. At this time there is. sudden increase in LH (Lutenizing hormone) from anterior pituitarf gland,which cause ovum to -elease,
ii) Luteum phase or l- phase: The endometrium is now divided into 3
layer

Compact (Superficial) layer.
Spongy (Intermediate) layer .
Basal layer

During ‘last’ 2·3 days of this phase oedema of spongy layer disappeared and blood vessels are shrinked and hemorrhagic areas appear.
If Fertilization Occur: The Mem,turation ‘does not occur, and the fertilized ovum start to grow and take nourishment from secretions of secretory phase, and get enter into tne Luteurn phase of ovarian cycle.
Corpus leutin works till 12 weeks.
If Fertilization does not occur: Menstruatic~l’ occurs ‘with, released of blood withs hedded epithelial cells, gl,:mdutar secretions .and unfertilized ovum and corpus luteum degenerates .jft r 4-5 days ofwor!<ing.

OR Define endocrine glands. Describe Pituitary gland as Master  gland.
Endocrine Glands: “The glands which do not have ducts and ·they pour their secretions directly into blood stream are called endocrine g ands and their secretions are called “Harmones”, They are also called ductless glands.”
The important endocrine glands In our body system are as follows,

Answer

Answer

1- Anterior lobe or pars anterior.
2- .Median space or pars Intermedia.
3- Posterior lobe or pars Posterior.
Anterior lobe: Six hormones are released from anterior lobe.
i) Growth Hormone (GH):
It effects growth rate of an organism and its skeleton in particular .
The excessive secretion of this hormone before maturity of an individual results in “Gigantism”
Deficiency of this (G.H) hormone results in “Dwarfism” in which the hormone is released long time after maturity which causes short
height ofthe individual.
In adults its excess results “ACROMAGAL yo.
ii) Adrenocorticotropic Hormone (ACTH): It controlls secretions of hormones frorr =drenal cortex (i.e. cortex of adrenal gland).
iii) Follicle-Stimulating Hormone (FSH): It stimulates growth 0’1 graffian follicles in ovary.
iv) Thyroid-Stimulating Harmone (TSH): It acts on thyroid gland to produce thyroxine.
v) Prolactin: It stimulate mammary glands to produce milk.
vi) Luteinizing Hormone (lH): It stimulates ovutation and formation of
corpus luteum.
II-Median Lobe: The hormone MSH i.e. Melanocytes stimulating hormone is released from it which acts on melanocytes to produce melanin pigments from skin.
III-Posterior lobe: Two hormones are released from posterior lobe.
i) Oxytocin:
It controls regression of uterus during parturation (child birth) ~
It helps in ejection of milk from mammary gland during lactation.
ii) Vasopressin:
It is also called Antidiuretic hormone (ADH).
It regulates amount of water in the body by increasing the reabsorption of water from kidney.

4. Describe Nerve impulse under the following headings:
(a) AMP .
(b) RMP
(c) SYNAPSE
Nerve impulse is an electrochemical signal developed by a neuron for communication and coordination. The mechanism is as follows.
i) Resting membrane Potential (RM.P)
ii) Action Potential (A.P)
iii) Propagation of impulse
iv) Synapse. .
i) Resting membrane Potential (R.M.P): The resting membrane potential of neurons ranges from (-40 mv to -90 mv) Usually it is (-65 mv). This potential is due to ions present on both sides of membrane (neurolemma). More sodium ions (positive) are present out side membrane than inside. Similary, more potassium ion inside than outside. Also the negative ions like protein and organic acids are accumulated .inside, the membrane. So there is positive charge outside and negative charge inside the cells.

ii) Action Potential (A.P): It is temporary or local reversal of polarity of neurolemma. This change is due to electric shock, touch, sound, vibration etc. Action potential consist of two parts.
1- Depolarization
2- Repolarization

1. Depolarization: In this phase the polarity of neurolemma changes to +40 mv. This change is due to travelling of sodium ions from outside to inside of cells.
2. Repolarization: In this phase the sodium channels (gates) are shut down and the potassium ions start to move outwards and the potential becomes (-65 mv).
The A.P takes only few milliseconds to take place.

iii) Propagation of Impulse: The A.P which is generated in neuron, it spreads along the entire length of axon (Neurolemma).

iv) Synapse: The site where the impulse move from one neuron to other is called Neuro- neuronal synapse and if the impulse move.from one neuron to the cell membrane of muscle fiber it is called myo-neuron synapse or motor end plate.
The synapse consist of
1- Pre synaptic membrane (Axon terminal)
2- Synaptic cleft (narrow space)
3- Post-synaptic membrane (Dendrite of other neuron or muscle cell membrane)

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5. Describe Darwin theory of Natural selection and the objections raised against it.
The word ‘evolution’ refers to’ the gradual development of something i.e. evolution of earth, evolution of man, evolution of plants and so on and so forth. The evolution with reference to plants or animal or both is referred to as organic evolution. Broadly, evolution can be said to be the development of an entity in the course of time through gradual sequence of changes from simple to complex state. Organic evolution is the qrsdual and orderly development of living organism from simple and unorganized form to complex and organized

Darwin’s Theory of Evolution
Introduction: Charles Darwin alonqwith- another scientist Wallace worked together and in 1858 Darwin published his famous book “THE ORIGIN OF SPECIES” by means of “NATURAL SELECTION”.
In his book he proposed the theory ofevolution. The theory explains the origin of species and hence of evolution. postulates of the Theory: The theory Of natural selection proposed by
Darwin has following points.
1- Over production
2- Str.Jggle for existance
3- Variations
4- Survival of the fittest or natural selection.
5- Structural modification

1-Over. Production: Darwin pointed out that all the living. organisms have high rate of reproduction. Each and every living organism produce . more individuals that can survive .
Evrttence and Examples:
Example 1: The cod fish lays 5-7 million eggs and if all eggs develop into fish, oceans of world would soon be chocked with cod fish.
Example 2: The elephant is the slowest breeder. It reaches reproductive age at 30 years and continue to produce offsprings till the age of 90. During this period a single female produces 6 young ones.
Darwin conclude that after a period of 750 years, single pair of elephant can produce nineteen million descendents.
2-Struggle for Existance: The tendency of organisms to produce greater number of offspring than it can possibly survive results in sever competition for food, for space and other essentials of life this is called struggle for existance.

There are three types of struggle.
(i) Interspecific Struggle: It is the competition between differente species to get available benefits.
(ii) Intraspecific Struggle: It is the competition between members of the same species. It is much more fierce and’ dangerous than interspecific struggle.

 

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(iii) Enviromental Struggle: It is the struggle of survival against the catastrophies, seasonal chanqes, enviromental horrors and climatic factors
3 Variations: Organisms of the same species are not similar to each other Instead they are sltghtely different from each other. This IS called vanations
4- Natural Selection or Surv’val of the Fittest: Some species possess more usefull vanations and are therefore. better adapted to their environment than the others This Individual was called by Darwin as fittest or natural selection
5- Structural Modifcatlons (Formation of New Species)’ Individual with usefull vanations I. . fittest live to maturity and transmit their favourable vana Ions to their offsprings. The selective process continuous genera ‘on te generation and in the course of a very long. time these favourable var.atons accumulate to such an extent that the species is modified this IS called origin of species.
Hence the gist f Darwm= theory IS,
“In any vaned population of organisms only the best adapted to that envirornent will tend to survive and reproduc I Objections of Darwinism. Although Darwin’s theory of Natural sel chon was so reasonable and well suported by arguments and examples Thu It was soon accepted by many biologists, but stili have som 0 the objections which are as under.
Larwm was unalbe to explain the origin of variation. Sm .l vanation can not be responsible for origin of new species H . did not mention about natural variation.
3- He d-d not rr.entlon the role of mutation In evolution.
4- He d.d not exp’ain ‘he presence of vestigial structures in the body of new orqan=rn
5· He did nol explain the over specilization of certain structures. his theory explains the survival of fittest not the arrival of fitte

Posted on January 5, 2016 in 2nd Year 2015 Karachi Board Past Papers

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