IGNOU FST CHAPTER 11 Q2

Q)What is the big bang theory of the origin of the universe?List three evidences in support of this theory.
Ans)The formation of the solar system is based on the assumption that sun and all the planets were formed a huge rotating cloud of huge rotating interstellar gas and dust.For some reasons the clouds started contracting.The contraction was hastened by its gravitational pull. The cloud continued to contract.It also rotating faster and become disc shaped. More and more clouds contracted towards the center of the disc forming the star-to be the new sun.The temperature of this star rose due to contraction until it started generating its own energy. Revolving around the sun was a disc of gas and dust from which the planets condensed. In this revolving disc, the lighter elements were thrown towards the periphery and the heavier elements were concentrated inwards.As the sun's energy increased the gas shells around the inner planets were driven off and only the cores of heavier elements in the cloud remained.The outer planets were less affected. Finally the bright star's radiation removed the last of the system's free gases and a mixed array of planets remained.

IGNOU FST CHAPTER 22 Q3

Q)What is vaccination? How does it protect us from infections? Name any four diseases that are prevented by vaccination.
Ans)The w.b.cs produce anti-bodies which neutralize the toxins by the invaders. The w.b.cs are of different kinds and each kind consists of millions of cells which recognize and combat a specific foreign invader. Once a class of WBC's has encountered a particular kind of invader, it develops memory and is trained to ward off future attacks. In this way the body becomes immune to that infection and that process is called immunization.
Our body regularly develops natural immunity as a variety of fighting cells are produced by actual attacks of infectious agents.Artificial immunization is a clever idea. It is done by vaccination that is by artificial introduction into the body of a weak infection, which triggers a defense mechanism and produces wbc's trained to combat that particular infection.
Tetanus, hepatitis-b,polio and measles are the four diseases that can be prevented by vaccination.

IGNOU CHAPTER 1 Q14

Q)Distinguish between theory and hypothesis. Give an example in support of your answer
Ans)Theory
A theory is a set of few general statement that can correctly describe or explain all experimental observation about the properties  and behavior of a large number of varied objects, phenomena, situation or systems.
Hypothesis
A hypothesis is a statement put forward on the basis of reasoning about the things that are studied. It is an attempt to answer and question the attempts that are posted.
e.g..
(a)Questions arising from observations based on previous knowledge.
      Why are bees attracted to flowers.
     
(b)Framing Hypothesis
      (i)bees are attracted to flowers by nectar in the flower
      (ii)bees are attracted by color of  the flowers
      (iii)bees are attracted by both
(c)Setting up an experiment to test the hypothesis
      (i)bees are let inside a chamber containing artificial flowers
      (ii)bees are let inside a chamber containing real flowers.
(d)Taking further observations
      (i)bees are attracted to the artificial flowers, sit on them but fly away in a few seconds
      (ii)bees sit on real flowers and remain there for long
(e)Framing laws and theories on the basis of results
       bees are attracted to flowers due to color and nectar.    

IGNOU FST CHAPTER 19 Q1

Q1)What is mixed cropping?Give an example. State three advantages of this agrotechnique.
Ans)Since cultivable land is limited the only way to meet our growing food needs is by growing two or more crops in a year from the same piece of land. Such multiple cropping practices would generate more employment in rural areas and also fulfill our food needs. In mixed cropping compatible crops like chickpea and mustard are sown in parallel rows with wheat pigeon pea mung bean, groundnut soybean and cow pea can be grown in between rows of rows of sorghum of maize or sugarcane or cotton. Such inter-cropping system generate additional employment opportunities.