Chlorophyll is found in virtually all photosynthetic organisms, including green plants, cyanobacteria, and algae. It absorbs energy from light; this energy is then used to convert carbon dioxide to carbohydrates. The chlorophyll molecule consists of a central magnesium atom surrounded by a nitrogen-containing structure called a porphyrin ring; attached to the ring is a long carbon-hydrogen side chain, known as a phytol chain. Variations are due to minor modifications of certain side groups. Chlorophyll is remarkably similar in structure to haemoglobin, the oxygen-carrying pigment found in the red blood cells of mammals and other vertebrates.

• The demography branch of geography deals with the composition of a particular human population.
• It is identified as the statistical study of the human population.
• It majorly studies population and spatial changes ( birth, death, migration, etc. )
• Demography is generally of two types :
• Formal Demography: The study of the measurement of population processes.
• Social Demography: Analyses the relationships between economic, social, cultural, and biological processes influencing a population.

Bio-gas is produced by the decomposition of waste organic matter like crop residue, sewage, vegetable waste in the absence of oxygen. Since the starting material is mainly cow-dung, it is also known as ‘gobar-gas’.

The organic waste material like crop residue, sewage, vegetable waste is collected inside a sealed chamber in which there is no oxygen. Anaerobic micro-organisms that do not require oxygen break down these complex compounds. Decomposition process produces gases like methane, carbon dioxide, hydrogen, hydrogen sulphide.

Biogas is an excellent fuel and contains 75% methane. It burns without smoke, leaves no residue like ash in wood, charcoal and coal burning. Its heating capacity is high.

The slurry left behind in sealed chamber after producing biogas can be taken out and be used as manure (rich in nitrogen and phosphorus), thus providing efficient and safe method of waste disposal.

• Integrase enzyme is produced by HIV that allows the integration of HIV DNA into the host cell's DNA.
• The integrase-HIV DNA complex is part of an intracellular nucleoprotein particle known as the "preintegration complex" (PIC).
• This complex consists of linear HIV DNA, viral proteins, and host proteins.

The speed of sound does not depend on frequency. If a sound wave is propagated from one medium to another, then its speed and wavelength change but its frequency remains constant. Hence, option C is the correct answer.

GNP = GDP + NFIA (net factor income from abroad). NFIA may be positive or negative. In case of India, it is negative; so our GDP > GNP

Lord Ripon is known as the Father of Local Self Government in India. He introduced the concept of local self-government and passed the resolution in 1882.

• Jawaharlal Nehru was the Prime Minister of India during Indo-China war (1962).

• He served as the Prime Minister of India from its establishment as an independent nation in 1947 until his death in 1964.

• He adopted the "Forward Policy" of setting up military outposts in disputed areas of the Sino-Indian border.

• China attacked some of these outposts, and thus the Sino-Indian War began (1962).