Question 1:

What advantage over an aquatic organism does a terrestrial organism have with regard to

obtaining oxygen for respiration?

Answer

Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals need to utilize

oxygen present in the water. Air contains more O2 as compared to water. Since the content of O2

in air is high, the terrestrial animals do not have to breathe faster to get more oxygen. Therefore,

unlike aquatic animals, terrestrial animals do not have to show various adaptations for better

gaseous exchange.

Question 2:

What are the different ways in which glucose is oxidized to provide energy in various organisms?

Answer

Glucose is first broken down in the cell cytoplasm into a three carbon molecule called pyruvate.

Pyruvate is further broken down by different ways to provide energy.

The breakdown of glucose by different pathways can be illustrated as follows.

In yeast and human muscle cells, the breakdown of pyruvate occurs in the absence of oxygen

whereas in mitochondria, the breakdown of pyruvate occurs in the presence of oxygen.

Question 3:

How is oxygen and carbon dioxide transported in human beings?

Answer

Haemoglobin transports oxygen molecule to all the body cells for cellular respiration. The

haemoglobin pigment present in the blood gets attached to four O2 molecules that are obtained

from breathing. It thus forms oxyhaemoglobin and the blood becomes oxygenated. This

oxygenated blood is then distributed to all the body cells by the heart. After giving away O2 to the

body cells, blood takes away CO2 which is the end product of cellular respiration. Now the blood

becomes de-oxygenated.

Since haemoglobin pigment has less affinity for CO2, CO2 is mainly transported in the dissolved

form. This de-oxygenated blood gives CO2 to lung alveoli and takes O2 in return.