Q20 of 40 Page 1

Write the structure and functions of placenta in a human female.

Placenta connects baby with mother’s body. It is a disc-like structure embedded in the uterine wall. It is a special tissue formed by the interlocking of two sets of villi, one set given by wall of the uterus and another set from the embryo. It is the site of exchange of materials between the blood of mother and baby. It provides nutrients, oxygen from mother to foetus and removes excretory substances, carbon dioxide from the foetus.


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19

Why are certain compounds called hydrocarbons? Write the general formula for homologous series of alkanes, alkenes, and alkynes and also draw the structure of the first member of each series. Write the name of the reaction that converts alkenes into alkanes and also writes a chemical equation to show the necessary conditions for the reaction to occur.

 20

Write the functions of each of the following parts in a human female reproductive system:

(i) Ovary


(ii) Uterus


(iii) Fallopian tube

 21

With the help of one example for each, distinguish between the acquired traits and the inherited traits. Why are the traits/experiences acquired during the entire lifetime of an individual not inherited in the next generation ? Explain the reason of this fact with an example.

 22

Analyse the following observation table showing a variation of image-distance (v) with object-distance (u) in case of a convex lens and answer the questions that follow without doing any calculations:


(a) What is the focal length of the convex lens ? Give a reason to justify your answer.


(b) Write the serial number of the observation which is not correct. On what basis have you arrived at this conclusion?


(c) Select an appropriate scale and draw a ray diagram for the observation at S.No.2. Also, find the approximate value of magnification.