Biology Today — January 2018

(Jacob Rumans) #1
Assertion & Reason

In each of the following questions, a statement of Assertion (A)
is given and a corresponding statement of Reason (R) is given
just below it. Of the statements, mark the correct answer as :


(a) if both A and R are true and R is the correct explanation of A
(b) if both A and R are true but R is not the correct explanation
of A
(c) if A is true but R is false
(d) if both A and R are false.



  1. Assertion : Genetic drift is an evolutionary force.
    Reason : Genetic drift occurs in all types of population
    but is markedly visible in population of large size.

  2. Assertion : Primitive atmosphere of earth was reducing.


Reason : Hydrogen atoms present in primitive atmosphere
combined with all oxygen atoms to form water, leaving
no free oxygen.



  1. Assertion : Fossil ostracoderms probably evolved from
    unarmoured ancestors such as Jamoytius.
    Reason : Before extinction, ostracoderms gave rise to
    first bony fishes.

  2. Assertion : Balanced polymorphism occurs when
    different forms co-exist in the same population in a stable
    environment.
    Reason : In humans, the existence of A, B, AB and O blood
    groups represent balanced polymorphism.

  3. Assertion : Cro-Magnon man is regarded as most
    primitive ancestor of Homo erectus.
    Reason : Cro-Magnon man was first tool maker and
    used tools of chipped stones.


Figure Based Questions


  1. Refer to the given figure and answer the following questions.


Water out

Water in
Water droplets

Water containing
organic compounds

Boiling water

D

A

B

C

Gases

(a) Identify the given figure and the labelled parts A, B, C
and D.
(b) In the given experiment, which gases were used to
simulate primitive atmosphere?
(c) Briefly describe the experiment given in the figure.


  1. Refer to the figures given below and answer the following
    questions.


P Q R S
(a) Identify the diagrammatic structures P, Q, R and S.
(b) What do these structures signify?
(c) Give an example of organs showing similar relationship.
(d) What type of evolution do these structures represent?

SOLUTIONS


CHAPTER-5 : PRINCIPLES OF INHERITANCE AND VARIATION



  1. (c) 2. (b) 3. (b) 4. (b) 5. (a)

  2. (d) 7. (a) 8. (b) 9. (a) 10. (a)

  3. A-(iii), B-(v), C-(i), D-(ii), E-(iv)

  4. A-(iv, x), B-(iii, ix), C-(i, viii), D-(ii, vii), E-(v, xii), F-(vi, xi)

  5. (i) Sutton and Boveri (ii) T.H. Morgan
    (iii) gametes (iv) chromosomes
    (v) genes (vi) meiosis
    (vii) diploid chromosome number
    (viii) segregation
    (ix) law of independent assortment

  6. (c) 15. (a) 16. (a) 17. (d) 18. (b)

  7. (a) The above cross shows the inheritance of haemophilia,
    which is a sex-linked recessive disorder. It shows criss-cross
    type of inheritance.


(b) In the given cross, the ratio of carrier and diseased
offspring would be 1 : 1. If the carrier female (XXh) marries
a normal male (XY), four types of children are produced
as given by the cross (XX, XXh, XhY, XY). In other words,
50% boys as well as 50% girls receive the gene for
haemophilia through the Xh chromosome of their mother.
However, the defect does not appear in the girls because
of the presence of the allele for normal blood clotting
is found on one of the X-chromosome (XXh). Therefore,
the girls remain carrier. 50% of the males who receive
the defective gene for haemophilia (XhY) suffer from the
disease as the Y-chromosome does not carry any allele for
it.
(c) Colourblindness is another sex-linked recessive disorder,
that shows criss-cross inheritance.


  1. (a) W-Deletion; X-Duplication; Y-Inversion;
    Z-Reciprocal translocation

Free download pdf