Biology (Part-3) (CDS-Solved Paper)

Total Questions: 25

21. Deficiency of which of the following elements is responsible for weakening of bones? [Morning Shift-2014 (I)]

1. Calcium
2. Phosphorus
3. Nitrogen
4. Carbon Select the correct answer using the codes given below:

Correct Answer: (a) 1 and 2
Solution:

Deficiency of calcium and phosphorus is responsible for weakening of bone because bone is made up of calcium and phosphate both. Deficiency of nitrogen and carbon may affect proteins content leading to stunted body growth which may lead to protein energy disorder such as marasmus in childhood stage.

22. In a forest, animals like voles and wood lice feed on plant roots and barks, respectively. Among the other carnivores, foxes, shrews and owls are present in that forest. Following predictions are made by a group of observers who have visited the forest. [Morning Shift-2014 (I)]

1. If the roots of the tree develop a disease, then voles and foxes will starve and not the owls.
2. Population of voles is dependent on wood lice population through food web.
3. If owl population declines, it will indirectly affect wood lice population.
4. If barks of tree are affected due to a disease, then reduction of wood lice will affect the shrew population forcing owls to eat more voles.
Which of the above prediction(s) is/are correct?

Correct Answer: (b) Only 3
Solution:

If owl population declines, it will indirectly affect wood lice population because if owl population will decline the population of wood lice increases because owl is not available to eat the wood lice population.
Hence option (b) is correct.

23. Match the following. [Morning Shift-2014 (I)]

Correct Answer: (a)
Solution:

The correct matching is

24. Which one of the following elements is present in green pigment of leaf? [Morning Shift-2014 (I)]

Correct Answer: (a) Magnesium
Solution:

Magnesium is present in green pigment of leaf. The green pigment of leaf is chlorophyll molecule. Chlorophyll is chemically a tetrapyrrole structure in which Mg⁺⁺ is present in the centre. Phosphorus is an important component of nucleic acid, component of cell membrane.
Iron is associated with electron transport chain in photosynthesis and respiration. It is essential for chlorophyll synthesis. Calcium is present in middle lamella of cell wall in the form of calcium pectate. Calcium stimulates development of root hairs. It plays an important role in apical meristems and mitosis.

25. Two strands of DNA are held together by [Morning Shift-2014 (I)]

Correct Answer: (a) hydrogen bonds
Solution:

Two strands of DNA are held together by hydrogen bond. H-bond is formed between the bases of two strands. adenine pair with thymine by two H-bonds and guanine pair with cytosine by three H-bonds. Covalent bond is present between phosphoric acid and sugar in the form of phosphodiester bond. Electrostatic force and van der Waal’s forces do not present in DNA.