Q28 of 30 Page 1

(a) What is the law of dominance of traits? Explain with an example.

(b) Why are the traits acquired during the life time of an individual not inherited? Explain.


(a) Law of Dominance was based on the results of monohybrid cross (crossing plants with one contrasting characters).

● When two homozygous plants with one contrasting character are crossed, the character which is expressed in the F1 generation is known as the dominant character while the character which is not expressed in the F1 generation is known as recessive character.


● Example: If pure or homozygous tall plants (TT) are crossed with pure homozygous dwarf plant (tt), then we obtain all the plants in F1 generation (100%) as tall plants.



The appearance of all tall pants proves the law of dominance.


(b) Acquired traits are the changes in the body which are not passed onto the offspring because these do not cause any change in the DNA/Germplasm of the gametes/reproductive tissues.


The absence of tail in the mouse after surgical removal and low weight of a starving beetle cannot be passed on to the progeny as they are acquired traits and they do not cause any change in the DNA of germ cells. These changes occur in somatic tissues hence are not transmitted to their progeny. Whereas a rudimentary eye of Planaria is controlled by specific genes present in germ cells which can be transmitted from generation to generation.


More from this chapter

All 30 →
26

The position of certain elements in the Modern Periodic Table are shown below.

Using the above table answer following questions giving reasons in each case :


(i) Which element will form only covalent compounds?


(ii) Which element is a non-metal with valency 2 ?


(iii) Which element is a metal with valency 2 ?


(iv) Out of H, C and F which has largest atomic size?


(v) To which family does H, C and F belong?


OR


Define atomic size. Give its unit of measurement. In the modern periodic table what trend is observed in the atomic radius in a group and a period and why is it so?


 27

(a) Why is there a difference in the rate of breathing between aquatic organisms and terrestrial organisms? Explain.

(b) Draw a diagram of human respiratory system and label – pharynx, trachea, lungs, diaphragm and alveolar sac on it.


OR


(a) Name the organs that form the excretory system in human beings.


(b) Describe in brief how urine is produced in human body.


 29

Draw a ray diagram in each of the following cases to show the formation of image, when the object is placed:

(i) between optical centre and principal focus of a convex lens.


(ii) anywhere in front of a concave lens.


(iii) at 2 F of a convex lens. State the signs and values of magnifications in the above-mentioned cases (i) and (ii).


OR


An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirror of focal length 15.0 cm


(i) At what distance from the mirror should a screen be placed in order to obtain a sharp image?


(ii) Find the size of the image.


(iii) Draw a ray diagram to show the formation of image in this case.


 30

(a) What is an electromagnet? List any two uses.

(b) Draw a labelled diagram to show how an electromagnet is made.


(c) State the purpose of soft iron core used in making an electromagnet.


(d) List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.