How are the alveoli designed to maximise the exchange of gases?
Exchange of the gases takes place in the alveoli. They have a balloon- like or pouch like structure which provides the maximum area for the exchange of gases. Alveoli are the tiny air sacs made up of squamous epithelium, which are present in the lungs and are thin walled, network of blood vessels are present for the exchange of gases. Numerous alveoli in the lungs show the maximum area for the exchange of gases between the air in the alveoli and into the blood in their surrounding capillaries and diffusion of oxygen occurs through this way. And, the diffusion of carbon dioxide occurs from the blood through the thin walls into the alveoli.
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
How is the amount of urine produced regulated?
What are the different ways in which glucose is oxidised to provide energy in various organisms?
What criteria do we use to decide whether something is alive?
The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm. (c) chloroplast.
(b) mitochondria. (d) nucleus.
What are the differences between autotrophic nutrition and heterotrophic nutrition?
What are the components of the transport system in highly organised plants?
What would be the consequences of a deficiency of haemoglobin in our bodies?
What are outside raw materials used for by an organism?
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Find the focal length of a convex mirror whose radius of curvature is 32 cm.
Why are carbon and its compounds used as fuels for most applications?
Which element has
(a) two shells, both of which are completely filled with electrons?
(b) the electronic configuration 2, 8, 2?
(c) a total of three shells, with four electrons in its valence shell?
(d) a total of two shells, with three electrons in its valence shell?
(e) twice as many electrons in its second shell as in its first shell?
Why are some substances biodegradable and some non-biodegradable?
State two ways to prevent the rusting of iron.
Explain different ways to induce current in a coil.
Which of the following methods is suitable for preventing an iron frying pan from rusting?
(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) All of the above.
Why does dry HCl gas not change the colour of the dry litmus paper?
Do basic solutions also have H+(aq) ions? If yes, then why are these basic?
Plaster of Paris should be stored in a moisture-proof container. Explain why?