CBSE ANNUAL PAPER - 1999

BIOLOGY

(SET-I)

Time Allowed : 3 Hours

Max. Marks : 70

General Instructions :
(i) All questions are compulsory.

(ii) Marks for each question are indicated against it.

(iii) Q. Nos. 1-11 are very short answer type carrying one mark each only. Answer them in one word one sentence.

(iv) Q. Nos. 12-23 are short answer questions carrying 2 marks each. It is appropriate to answer them in about 30-50 words.

(v) Q. Nos. 24-28 are short answer questions carrying 3 marks each. It is appropriate to answer them in about 30-50 words,.

(vi) Q. Nos. 29-32 are long answer questions carrying 5 marks each. It is appropriate to answer them in about 40-100 words.

(viii) Do not unnecessarily make the answer lengthier than desired.

Section - A

Q. Nos. 1-8 are of very short 1-20 words each.

Name the process in which are bacteriophage picks up a piece of DNA from one bacterial cell and transfer the same to another bacterial cell on infection.

Which fraction of soil H₂O is readily available to plants for absorption ?

(i) Kidney

(ii) Urinary bladder.

(ii) Urinary bladder - Mesoderm.

What provided energy for abiotic synthesis on the primitive earth ?

Name the two curable sexually transmitted disease.

Section - B

Q. Nos. 9-18 .....20-30 words each.

In most plants the terminal bud suppresses the development of lateral buds. What is this phenomenon called. Name the phytohormone that can promote the phenomenon.

Apical Dominance. P_R Promotes this phenomenon.

Sieve tubes in angiousperms are associated with specialised paprenchyma cells. Name those cells. How do they help sieve tube members ?

Companion cells. They help in physiological functioning of sieve tubes.

Digested fats are covered with water molecules to form micelles. They are absorbed in this form and is transported as chylomicrons.

Muscles that work in opposite directions but from same plane are antagonistic muscles. For e.g. Flexor and extensor.

Describe the methods of birth control by which fertilization of Ovum by sperm is prevented.

The method is IUCD. In this method Copper - T or Loop is inserted in the uterus of female so that fertilization does not take place.

What is artificial selection in terms of evolution ? Name one plant that has been produced as a result of artificial selection.

It is a process in which hybridisation occurs between two organisms of desired characters. In plants cabbage, cauliflower and caulrabi are obtained from clueucort.

'Birds have evolved from reptiles'. How does palaentology provide evidence in support of the above statement ?

With the help of 'Archaeopteryx' we are able to find that birds have evolved from reptiles because it has beak with teeth, wings with claws and tail with vertebral column.

Who discovered the co-acervetes? List the biological properties of co-acervates.

(i) They are self-duplicating.

(ii) They are Chemoheterotrophs.

Mycorrhiza is a symbiotic association between fungus and roots of higher plants. It act as biofertilizer as its hyphae moves to the soil depth and bring minerals for the plants. They also store various minerals in their mantle.

When the body immune system, turns against its own body the diseases are auto immune diseases. For eg - AIDS, Chronic anemia.

Section - C

Q. Nos. 30-50 words each.

What is transformation? Describe Griffith's transformation experiment.

In 1928, an English bacteriologist, Fredrick. Griffith conducted experiments with the bacterium that causes pneumonia, Diplococus pneumonia. There are two main types of this bacteria, smooth (S) and routh (R). S-type cells have a capsule around capsule, are virulent and cause pneumonia. The R-type bacteria do not have the capsule and are avirulent and harmless. The S-type bacteria when injected into mice cuase pneumonia and subsequent death of the animal whereas the R-type bacteria when injected into mice are found to be harmless. Griffith found that the s-type bacteria when killed by heat prior to injection into mice did not cause the disease. However, when heat killed S-type bacteria were injected into mice along with a virulent, R-type bacteria, mice suffered from pneumonia and died. Examination of the dead mice revealed that death occurrred due to the living S-type bacteria. Griffith concluded from this experiment that the a virulent R-type bacteria bacteria had been transformed into S-type, capsule variety. In other words, the dead S-type bacteria had transmitted their virulence to the living R-type a virulent bacteria. This experiment showed that some component of the bacterial cell is responsible for the phenomenon of transformation.

What are linked genes ? Diagrammatically represent a cross between a white eyed female and red eyed male Drosphilia.

When genes are very closely present on the chromosomes so that they cannot be separated. They are called linked genes.

How does an excess of tryptophen cause "SWITCHING OFF" of the tryptophan Operon ?

When tryptophan is produced in excess it combines with repressor molecule to form co-repressor. This then kinds to the operator. The Switch of operator is off. It can no longer give order to structural genes and structural genes slopes the synthesis of tryptophane in the medium.

If biotic origin of life is in progress on a planet other than earth, what should be the conditions there ? Explain.

(2) Reducing atmosphere.

(3) High temp.

(4) Energy supply by UV radiations.

Oogenesis occurs in ovary. It is a process of formation of ova in the ovary. During this process egg mother cells produce oogania (2n). Oognia develops into primary oocytes. these primary oocyte under gomeiotic division as a result of which one functional OVA and three polar bodies are produced. Later on three small polar bodies disappears. Thus only one ocyte is functional. It is non motile, large sized ovum.

Describe the robe of red blood cells in the transport of oxygen and carbon dioxide by blood.

(i) Oxygen get attached to hemoglobin to form oxyhemoglobin and is transported in this form in the blood.

(ii) The three forms in which CO₂ is carried by blood in human body are :

(a) As bicarbonates of Na and K ( about 85 % of CO₂ is carried in this form).

(b) As carbiminohemoglobin With Hb ( 10 % of CO₂).

(c) As carbonic acid in plasma ( 0.5 % of CO₂).

(iii) Carbonic anhydrase.

Draw a diagram to show the cultural structure of human heart. Label six parts in all including at least three values.

What is metastasis ? List any four danger signals of cancer.

Danger signals of cancer :

(1) Any persistent lump in breast / tongue or lips.

(2) Any wound that does not heal up easily.

(3) Unusual bleeding from any part of the body.

(4) A rapid change in wart or mole.

(5) Change in bowel in wart of mole.

(6) Hoarseness in voice.

What is meant by biotic synthesis ? Who proposed this idea and who supported it experimentally.

In the beginning, the earth was very hot & everything was in gaseous form. Gradually, cooling took place. Life originated about 4600-3600 million years ago. Cyanobacteria like organism appeared first. The earth's atmosphere at that time was reducing. When complex molecules were formed from simple molecules present in the earth's primordial soup. The energy for these reactions came from heat, Cosmic rays and lightning. (Oparin - Haldane theory) Experimentally Urey & Miller supported the theory given by oparin Haldane.

1. Unwinding of interwinded DNA at several points by the action of enzyme helicase and topoisometrase.

2. unwinding of the strand give the DNA a Y shaped structure.

3. DNA polymerase start synthesizing new strand of DNA in 5 -- 3' direction this is known as leading strand.

4. It opposite direction it synthesize DNA fragment in 5'--x' these are called okazaki fragments.

5. These fragments are then joined together by the action of the enzyme ligase to complete the replication process.

Specify how C₄ photosythetic pathway increases CO₂ concentration in bundle sheath cells of sugarcane. How much is C₄ pathway more energy expensive than C₃ pathway.

The anatomy of leaves of C₄ plants is different from leaves of C₃ plants. This type of anotomy is called Kranz anatomy. In the leaves of such plants. Palisade tssue is absent. There is a bundle sheath around the vascular bundles. The chloroplasts in the bundle sheath cells present are large and without or less developed groove whereas in the mesophyll cells the chloroplasts are small but with well developed groove.

CO₂taken from atmosphere is accepted by 3 carbon compound. Pyruvate in the chloroplasts of mesophy II cells leading to the formation of 4-C compound the malic acid. It is transported to the Chloroplasts of bundle sheath cells. Here malic acid (C₄) is converted to Pyruvic acid (C₃) with the release of CO₂ . Thus concentration of CO₂ increase in the hundle sheath cells. These cells contain enzymes of calvin cycle. because of high concentration of CO₂ RuBP Carboxylase participate in calvin cycle is transported into the phloem.

Pyruvic acid generated in the bundle sheath cells re-enters mesophyll cells and regenerates phosphoenol pyruvic acid by consuming one ATP. Since the conversion results in the formation of AMP ( not ADP), needs 12 glucose molecule, whereas C₄ Pathway requires 30 ATP.

What is a synapse ? How is the nerve impulse transmitted across a synapse ?

Synapse is the junction between two neutrons where one axon gives the information to another through dendrites. Synapse is formed when the two meeting dendrictes looses its myelin sheath to form synaptic knob. this synaptic knobs are separated by synaptic claft filled with synaptic fluid. Messages are present within the synaptic knob in the form of chemicals like adrenaline or a acetylcholine. These chemicals are confined with in the synaptic vesicles . the vesicles carrying the chemicals moves from the donor dentrite to the recepient dendrite through synaptic fluid. Thus there is movement of messages from one neuron to another.