Download enhancement worksheet 1

INDIAN SCHOOL AL WADI AL KABIR
DEPARTMENT OF SCIENCE 2015 -16
Class XII
BIOLOGY
Date: 31/08/15
IMPORTANT QUESTIONS
1. Comment on the similarity between the wings of a cockroach and the wings of a bird.
What do you infer from the above with reference to evolution?
2. Why are analogous structures a result of convergent evolution?
3. (a) Rearrange the following in an ascending order of evolutionary tree:
Reptiles, salamander, lobefins, frogs
(b) Name two reproductive characters that probably make reptiles more successful
than amphibians.
4. Darwin observed a variety of beaks in small black birds inhabiting Galapagos Islands.
Explain. What conclusion did he draw and how.
5. How does the process of natural selection affect Hardy-Weinberg equilibrium?
Explain. List other four characters that disturb the equilibrium.
6. Explain the role of regulatory gene in lac operon. Why is regulation of lac operon
known as negative regulation?
7. Draw a schematic representation of transcription unit showing the polarity of both the
strands. Label the promoter gene and the template strand.
b) Mention the condition when template strand becomes coding strand.
c) Give the function of the promoter gene.
8. a) In human genome which one of the chromosomes has the most genes and which
one has the fewest?
b) Scientists have identified about 1.4 million snps in human genome. How is this
information of their existence going to help the scientists?
9. Study the flow chart given below and answer the questions that follow.
(a) S strain------into mice------mice dies
(b) R strain-------into mice-----mice lives
(c) Heat killed S strain + live R strain-------into mice----(A)
(d) Heat killed S strain+ DNAase ----------into mice-----mice lives
(d) Heat killed S strain+ DNAse+ live R strain-----into mice---(B)
(i) Name the organism and differentiate between its two strains R and S respectively
(ii) Write the results A & B obtained in step © & (d) respectively
(iii) Name the scientist who performed the steps a, b &c
(iv)Write the specific conclusion drain from the step (d)
(B)
10
(C)
(A)------DNA----------mRNA------protein. Look at the above sequence and mention
the events A, B & C.
(b) What does central dogma state in molecular biology? How does it differ in some
viruses?
11. (a) Write the types of sex-determination mechanisms the following crosses show.
Give an example of each type
(i)
Female XX with male XO
(ii)
Female ZW with male ZZ
(b) A colour blind child is born to a normal couple.
(i) Work out a cross to show how it is possible
(ii) Write the pattern of inheritance (Mendelian or chromosomal) and the nature of
gene responsible for this disease
(iii)Name an example for any other disease that follows the same pattern of
inheritance
12. (a)A pregnant human female was advised to undergo M.T.P. It was diagnosed by her
doctor that the foetus she is carrying has developed from a zygote formed by an XXegg fertilized by Y-carrying sperm. Why was she advised to undergo M.T.P?
13. How did Morgan show the deviation in inheritance pattern in Drosophila with respect
to law of independent assortment?
14. Explain how the trisomy of 21st chromosome occurs in humans. List any four
characteristic features in an individual suffering from it.
15. Write the percentage of F2 homozygous and heterozygous populations in a typical
monohybrid cross.
16. Given below are the events in human reproduction. Write them in correct order:
Insemination, gametogenesis, fertilization, parturition, gestation, implantation.
17. The mother germ cells are transformed into a mature follicle through a series of steps.
Provide the missing steps in the blank space:
Oogonia
____
Primary follicle
_____
_____
Graafian follicle
18. Why does corpus luteum secrete large quantity of progesterone during luteal phase of
menstrual cycle?
19. Name the hormonal composition of the oral contraceptive used by human females.
Explain how it acts as a contraceptive.
20. Enumerate the complications that untreated STDs can lead to.
21. Draw the sketches of zoospore and conidium. Mention two similarities between them
and one feature common to both.
22. Honey bees produce their young ones only by sexual reproduction. In spite of this, in
a colony of bees, we find both haploid and diploid individuals. Analyze the reasons
behind it.
23. In an angiosperm embryo sac is haploid, embryo is diploid and endosperm is triploid.
Justify giving reasons for each stage.
24. Explain any three advantages the seeds offer to angiosperms.
25. Explain the process of emasculation and bagging of flowers. State their importance in
breeding experiments.
Prepared by,
Rejitha Sajith