Life and Processes

The oesophagus is a tube, which simply conducts food from the throat to the stomach. It does not produce any digestive enzyme. So, option 2 is correct.

Blood platelets help in clot formation. So, option 3 is correct.

Gases in mammals are exchanged inside alveoli through the process of diffusion. So, option 4 is correct.

The xylem tissue, vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant. So, option 4 is correct.

Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as urine flows along the tubular part of the nephron. So, option 3 is correct.

Option 2 is correct. Those organisms which are dependent upon other organisms for food are known as heterotrophs.

Option 2 is correct. It is due to imbibition that the seeds absorb water and swell up.

Lymph is a pale fluid made up of only WBCs and not RBCs. So, option 2 is correct.

The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg. So, option 4 is correct.

Oxygen is a by-product of photosynthesis and not a reactant, so photosynthesis can take place in the absence of oxygen. So, option 1 is correct.

O₂ is consumed by the tissue to release energy and CO₂ is released into the blood, which makes it dark. Option 3 is correct.

During respiration, energy is released in the form of ATP along with carbon dioxide and water. So, option 3 is correct.

Sometimes, when there is a lack of oxygen in our muscle cells, another pathway for the break-down of pyruvate is taken. Here the pyruvate is converted into lactic acid, which is also a three-carbon molecule. This build-up of lactic acid in our muscles during sudden activity causes cramps. 

During inhalation, the diaphragm becomes flattened to increase the surface area of the lungs so that more air can enter inside them. So, option 1 is correct.

The pharynx is the common passage for both the digestive and respiratory systems. So, option 4 is correct.

Hydrochloric acid creates an acidic medium, which facilitates the function of the enzyme pepsin. 

The phloem transports products of photosynthesis from the leaves where they are synthesised to other parts of the plant. 

The loss of water from the aerial part of the plant during day time is known as transpiration. So, option 2 is correct.

The inner lining of the small intestine has numerous finger-like projections called villi, which increase the surface area for absorption. So, option 4 is correct.

Since the blood emerges from the heart at a very high pressure, the arteries have thick, elastic walls. So, option 3 is correct.

The pH of the digestive juice (gastric juice) found in the stomach is 2, due to the presence of HCl.. So, option 1 is correct.

ATP is the energy currency of  animals and plants. So, option 3 is correct.

There are two pathways of breaking down of pyruvate, one in the presence of oxygen and another in the absence of oxygen. So, option 2 is correct.

Plants store waste products in the form of resins, latex, gums, etc. So, option 4 is correct.

The air passing through the nostrils is filtered by the fine hairs and mucus present in the nostrils. So, option 2 is correct.