Describe double circulation of blood in human beings. Why is it necessary?
Mammals like human beings, monkeys etc. have a double circulatory system and they include four chambered hearts (two auricles and two ventricles). Heart’s internal structure consists of auricles, ventricles, blood vessels, apertures and valves (contains various parts). As the blood passes through the heart twice during one cycle, this is known as double circulation of blood. Auricles act as the collecting chamber for the blood returning to the heart. They have to force the blood into the ventricles because of the thin wall of auricles; and ventricles act as the distributing chambers of the blood reaching the atria. Process of double circulation involves two parts – pulmonary and systemic circulation.
In pulmonary circulation, the exchange of blood takes place between heart and lungs. The deoxygenated blood from the right ventricle is pumped into the lungs through the pulmonary artery and from lungs oxygenated blood goes to the left auricle through the pulmonary vein; and from the left auricle the blood is pumped into the left ventricle.
In systemic circulation, the exchange of blood takes place between heart and body. The oxygenated blood from left ventricle is pumped into the aorta for further transportation of blood in the body and the deoxygenated blood from the body enters the right auricle through vena cava; and from right auricle the blood is pumped into the right ventricle of the heart by the body tissues.
Both pulmonary circulation and systemic circulation take place simultaneously.
This double circulation is necessary for the regulation and the maintenance of the body temperature.
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Outline a project which aims to find the dominant coat colour in dogs.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
How is the sex of the child determined in human beings?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
What is an homologous series? Explain with an example.
Why is variation beneficial to the species but not necessarily for the individual?
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
What is an homologous series? Explain with an example.
Give an example of a double displacement reaction other than the one given in activity 1.10.
Calculate the number of electrons constituting one coulomb of charge.
Suggest some approaches towards the conservation of forests.
Where do plants get each of the raw materials required for photosynthesis?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
What would be the consequences of a deficiency of haemoglobin in our bodies?
You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table 10.3.
Material medium |
Refractive index |
Material medium |
Refractive index |
Air | 1.0003 | Canada Balsam |
1.53 |
Ice | 1.31 | ||
Water | 1.33 | Rock salt | 1.54 |
Alcohol | 1.36 | ||
Kerosene | 1.44 | Carbon disulphide |
1.63 |
Fused quartz |
1.46 | ||
Turpentine oil |
1.47 | Ruby | 1.71 |
Benzene | 1.50 | Sapphire | 1.77 |
Crown glass |
1.52 | Diamond | 2.42 |
How is oxygen and carbon dioxide transported in human beings?
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.