SECTION - A

1. Pick out the ancestral line of conifers from the list of plants
   given below :
   Seed ferns, Cycads, Herbaceous lycopods, Psilophyton,
   Gnetales.


2. How can be the population density of tigers measured?


3. What do you understand by monosporic type of development
   of embryo sac?


4. How does intake of tobacco raises blood pressure?


5. The egg of a normal animal contains 10 chromosomes, of
   which one is X chromosome. How many autosomes would
   be there in the karyotype of somatic cells of this animal?
   SECTION - B


6. Why are the DNa fragments with sticky ends preferred over
   the DNa fragments with blunt ends to generate a chimeric
   DNa molecule?


7. (a) The gene I that controls abO blood grouping in humans
   has three alleles Ia, Ib, and i. How many different genotypes
   and phenotypes are likely to be present in the human
   population?
   (b) What is the source of heroin? Mention its one effect on
   human body.


8. Why the complete removal of gonads cannot be considered
   as a method of contraception?


9. How is CuT different from LNG – 20?

OR

Select two pairs from the following which exhibit convergent

evolution. Give reasons for your answer.

(a) Forelimbs of man and horse

(b) Wings of insects and birds

(c) Mouth parts of mosquito and cockroach

(d) Pectoral fins of sharks and flippers of dolphins

10. Give two reasons to explain why there is more species
    biodiversity in tropical latitudes than in temperate ones.
    SECTION - C


11. (a) In a pea plant, round and yellow seeds are dominant over
    wrinkled and green seeds. Work out the number of genotypes
    and phenotypes of a cross between a heterozygous pea plant
    and a homozygous dominant pea plant.
    (b) How do you relate dominance, codominance and incomplete
    dominance in the inheritance of characters?


12. With the help of suitable graphs, illustrate how natural
    selection leads to directional change.


13. Give reasons for the following:
    (a) Transcription and translation in bacteria are coupled.
    (b) DNa replication is discontinuous on the template strand
    with polarity 5′ → 3 ′.


14. (a) How are amniocentesis and chorionic villi sampling
    (CVS) different from each other?
    (b) Where and why would the rate of succession be faster - in
    a newly created pond or a forest destroyed by forest fire?

GENERAL INSTRUCTIONS

(i) all questions are compulsory.

(ii) This question paper consists of five Sections a, b, C, D and e. Section a contains 5 questions of one mark each. Section b contains

5 questions of two marks each, Section C contains 12 questions of three marks each. Section D contains 1 question of VbQ type with

four marks and Section e contains 3 questions of five marks each.

(iii) There is no overall choice. However, an internal choice has been provided in one question of 2 marks, one question of 3 marks and all the

three questions of 5 marks weightage. a student has to attempt only one of the alternatives in such questions.

(iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.

BOARD

CB SE

PRACTICE PAPER 2016

21 stMarch

Exam on

Time allowed : 3 hours Maximum Marks : 70