CBSE Set Qa1 Biology Sample Test Papers For Class 12th for students online
Biology Class-Xll
(CBSE)
You are on answers 1 to 20
Q.1 Which of the
movable joint makes the hip joint ?
Ans1. Ball and socket joint.
Q.2 Write the
full form of tRNA.
Ans2. Transfer Ribosenucleic Acid.
Q.3 Mention any
two factors by which the environment or the nature checks the pollution size.
Ans3. (i) Competition and struggle.
(ii) Drought and flood.
Q.4 Give two
examples of analogous organs from animals.
Ans4. Wings of :
(i) an insect,
(ii) a bird, and
(iii)a bat are analogous organs.
Q.5 Mention one
difference in the structure of chlorophyll-a and chlorophyll-b.
Ans5. Chlorophyll-a has a methyl (-CH3) group whereas
chlorophyll-b has an aldehyde (-CHO) group.
Q.6 Name the source glands of glucagon and parathormone.
Ans6. Glucagon : Islets of Langerhans in Pancreas
Parathormone: Parathyroid gland
Q.7 Mention one difference between benign tumour and
malignant tumour.
Ans7. A malignant tumour is different from a benign tumour in the formers
capacity to undergo metastasis.
Q.8 Name any two structures in our body, which bear ciliated
epithilium.
Ans8. (i) Kidney tubules, and
(ii) Fallopian tubes
Q.9 A women travels in a crowded compartment along with
people suffering from diabetes, influenza and amoebiasis. With which one of
these diseases she is most likely to be infected during this journey and why ?
Ans9. Influenza; because among diabetes, influenza and amoebiasis only
influenza is a disease communicable through air.
Q.10 Amongst pea tendrils, opuntia spines, lemon thorns and
cucurbit tendril, which ones are homologous structures ? Give reason.
Ans10. Pea tendrils are homologous to Opuntia spines because both are
modifications of leaves; lemon thorns are homologous to Cucurbit tendril because
both are modified stems.
Q.11 Describe one example of artificial selection.
Ans11. Cabbage, cauliflower and kohlrabi are derrived from a comman
ancestor, colewort by artificial selection.
Q.12 Mention two differences in the vascular bundles of
Sunflower and Maize stems
Ans12. Sunflower and maize stems are different in that :
(1) Sunflower has radially arranged, fewer vascular bundles, whereas maize has
randomly distributed numerous vascular bundles.
(2) Sunflower has open (with cambium) vascular bundles, whereas maize has closed
(without cambium) vascular bundles.
Q.13 Give any four examples of human reflexes.
Ans13. (1) Salivation on the sight or smell of a tasty food.
(2) Constriction of pupils on the illumination with bright light.
(3) Blinking of eye lids on the approach of an object close to the eyes.
(4) Jerk in the legs when a pin pricks sole.
Q.14 How were exact replicas of master plate obtained in
Lederberg replica plating experiment ?
Ans14. A sterile velvet disc, mounted on a wooden bloc, was gently pressed
on the master plate. Some bacteria from each colony adhered to the velvet. By
pressing this velvet on to new agar plates, Ledeberg and Lederberg obtained
exact replicas of the master plate because the few bacteria
transferred by the velvet formed colonies on the new plates.
Q.15 In humans, genetically the sex of the child is
determined by the father and not by the mother. Explain
Ans15. Human male is heteromorphic with respect to chromosome: XY. A son
gets one of its chromosomes from the father and the other from the mother. The
mother being homomorphic contributes only X. If the father contributed X, the
embryo develops into a daughter, whereas if he contributed Y, the embryo
develops into a son.
Q.16 Describe how auxins are related with the bending of
shoots towards the source of light ?
Ans16. Auxins promote elongation and growth of stem by stimulating cell
walls to stretch. Auxin is present in the tip of the coleoptile and moves away
from the illuminated side. Once the concentration of auxin increases in the
nonilluminated side, differential growth begins and causes bending of the tip
towards the source of light.
Q.17 Explain any two palaeontological evidences in favour of
organic evolution.
Ans17. (i) Archaeopteryx provides evidences for the evolution of birds from
reptiles.
(ii) Fossils provide evidences of the evolution of modern day horse (Equus) from
Eohippus- Mesohippus.
Q.18 Distinguish between bacterial transduction and
bacterial transformation.
Ans18.
|
Transduction |
Transformation |
|
Transfer of the DNA from one bacterium to the other, mediated through a bacteriophage. The carried DNA bestows some of the properties of the donor to the acceptor bacterium. |
Transfer of the DNA from one bacterium to the other through the solution phase, after which the acceptor bacterium gets the properties of the donor bacterium. |
Q.19 Mention
four aspects in which uricotelism differs from ureotelism.
Ans19.
|
Ureotelism |
Uricotelism |
|
(1)Nitrogen is mainly excreted as urea. (2)Urea is very water-soluble and therefore can be used as the excretory material only if the animal can afford to have a lot of water. (3)Urea formation requires more energy than ammonia. (4)This mode is most suitable for those animals, which can excrete sufficient volumes of water, or can concentrate urea considerably in the urine, or can retain considerable amounts of urea in their blood. |
(1)Nitrogen is mainly excreted as uric acid. (2)Uric acid is water insoluble and
therefore can be excreted without much intake of water. (3)Uric acid formation requires much more energy than the formation of urea. (4)This mode is most suitable to the land animals of drier zones and birds, which have a limited access to water. |
Q.20 Specify how
a pentose phosphate is a CO2 acceptor in the dark reaction of
photosynthesis.
Ans20. 3 molecules of a pentose phosphate (ribulose bisphosphate) accept 3
molecules of CO2 and this carboxylation is mediated by the enzyme
RUBISCO. The 3 molecules of six-carbon intermediate, which form are short-lived
and break down into two molecules of three-carbon phosphoglyceric
acid each.The 6 molecules of phosphoglyceric acid carry the rest of the dark
reaction cycle.