The reaction of calcium with water is less violent. So, the heat released is not sufficient for the hydrogen to catch fire. Calcium starts floating because the bubbles of hydrogen gas which are formed during the reaction stick to the surface of the metal and hence calcium floats on water.
2
Give one reason why multicellular organisms require special organs for exchange of
gases between their body and their environment.
Ans
A reason is that multicellular organisms need special organs for exchange of gases with the environment because of prokaryotic cells found in the body. The cells are not in contact with the environmentand therefore diffusion would not work in the exchange of gases.
3
What is‘translocation’in plants?
Ans
The reaction of calcium with water is less violent. So, the heat released is not sufficient for the hydrogen to catch fire. Calcium starts floating because the bubbles of hydrogen gas which are formed during the reaction stick to the surface of the metal and hence calcium floats on water.
4.
State the functions of plant hormones. Name four different types of plant hormones.
Ans
The four plant hormones and their functions are as follows:
- Auxin: It promotes cell enlargement and cell differentiation in plants.
- Gibberellins: It breaks the dormancy in seeds and buds.
- Cytokinins: It promotes cell division in plants.
- Abscisic acid: It promotes the closing of stomata.
5
What is a sex chromosome?
Ans
A sex chromosome is a type of chromosome involved in sex determination. Humans and most other mammals have two sex chromosomes, X and Y, that in combination determine the sex of an individual. Females have two X chromosomes in their cells, while males have one X and one Y.
6.
How is the equal genetic contribution of male and female parents ensured in the progeny?
Ans
The gametes of both the male and the female parent have half the genetic information required for the offspring. Hence, 23 chromosomes are inherited from the father and 23 chromosomes from the mother. Hence, there is an equal contribution of male and females to the offspring
7.
The refractive index of diamond is 2.42”. What is the meaning of this statement in relation to
speed of light?
Ans
Because diamond has a refractive index of 2.42, the speed of light in it is reduced by a factor of 2.42 when compared to the speed of light in air. To put it another way, the speed of light in a diamond is 1/2.42 that of light in vacuum.
8
Q.What is meant by the term ‘frequency of an alternating current’? What is its value in India?
Why is an alternating current considered to be advantageous over direct current for long range
transmission of electric energy?
Ans
In India, frequency of AC is $50Hz$ , i.e. 50 cycles per second. When compared to direct current, alternating current is regarded to be more advantageous for long-distance transmission of electric energy since it can be transmitted over long distances to distant locations with little loss of electric power.
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