Monday, December 8, 2014


1. Name the tissue associated with the conduction water in plants. (1 mark)
Ans: Xylem tissue
2. What is source of O2 liberated during photosynthesis? (1 mark)
Ans: The main source of oxygen in the atmosphere during photosynthesis is photosynthetic [green] plants, cyanobacteria and algae which releases oxygen during photosynthesis. Other sources include the photolysis of atmospheric water and nitrous oxides by ultraviolet light and the free oxygen released from the silicates and mineral oxides present in the earth crust. 
3. In which part of the digestive canal food is absorbed? (1 mark)
Ans: small intestine
4. Which organelle of the cell is known as ‘power house’? (1 mark)
Ans: Mitochondria
5. Why oxygenated and deoxygenated blood is separated in mammals and birds? (1 mark)
Ans: Oxygenated and deoxygenated blood is separated in mammals and birds as Such kind of separation allows a highly efficient supply of oxygen to the body . Birds and mammals constantly use energy to maintain their body temperature.
6. Name the functional unit of human kidney. (1 mark)
Ans: Nephron is the basic structural and functional unit of the kidney.
7. ‘Respiration is a vital function of the body’. Justify. (2 marks)
Ans: Respiration is the bodily process of inhalation and exhalation.  Through this process, oxygen is inhaled.  T his inhaled oxygen is used to burn/oxidize/break down the food (glucose). This reaction produces energy which is used to carry out various activities going on in our body. Our body need continuous supply of energy to carry out these activities.  So, respiration is continuous processes which make us able to meet energy demand of our body. If respiration comes to halt the person will die
8. Differentiate between autotroph and heterotrophs. (2 marks)
Ans: Autotrophic nutrition means that the organism is preparing its own food and is not dependent on any other organism for food. Green plants are autographs.
Heterotrophic nutrition means that the organism does not prepare its own food and is dependent on other organisms for food. All organisms which are not among green plants are heterotrophic.
9. State the two vital functions of the human kidney. (2 marks)
Ans: Function of Kidneys:
a)    Absorption of water and salt
b)    Removal of waste materials like urea, ammonia etc from blood
c)    Blood pressure control
10. Mention the role of the valves in maintaining blood flow in the heart. (2 marks)

Ans: The valves present in the heart normally allow the blood to flow in only one direction. There are four valves in the heart – mitral valve, tricuspid valve, bicuspid valve and pulmonary valve. These valves control the flow of blood by opening and closing through the heart at the time of contraction.
11. What is the structural difference between the auricles and ventricles? (2 marks)
Ans: The arteries have thick, elastic walls. They do not have valves
The Veins do not  have thick, elastic walls. They have valves.
12. How are lungs designed in human beings to maximize the area for exchange of gases(3marks)
Ans: Within the lungs, the bronchi divides into smaller and smaller tubes called bronchus which finally terminate in balloon-like structures which are called alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli contain an extensive network of blood-vessels.
13. How are water and minerals transport in plants? (3 marks)
Ans: The components of xylem tissue (tracheids and vessels) of roots, stems, and leaves are interconnected to form a continuous system of water-conducting channels that reaches all parts of the plant. Transpiration creates a suction pressure, as a result of which water is forced into the xylem cells of the roots. Then there is a steady movement of water from the root xylem to all the plant parts through the interconnected water-conducting channels.
14. How is food transported in plants? (3 marks)
Ans: Food is transported in plants through phloem. The transport in phloem is an active process and involves use of energy. The energy in the form of ATP created osmotic gradient which results in transportation of food through phloem.
15. (i) What are the functions of liver and pancreas in the digestive system? (5 marks)
(ii) Which part of the body secretes bile? Where is bile stored?  (iii) What is trypsin? What is its function?
Ans:(i) Liver and pancreas play key roles in the digestive system. Liver secretes bile juice which helps in emulsification and digestion of fat molecules. It also aids in absorption of fat soluble vitamins like A, D E, K. While pancreas secrete pancreatic juice containing several enzymes that help in carbohydrate metabolism.
 (ii) Bile is secreted by liver. It is stored in the gall bladder till required.

 (iii) Trypsin is secreted by the duodenum of small intestine. When proteins are digested in the stomach the acidic medium is passed as such into the small intestine. The small intestine is incapable of handling such low pH and neither can its enzymes function. Hence Trypsin is released to neutralize the acidity

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