During biological nitrogen fixation, inactivation of nitrogenase  by oxygen poisioning is prevented by leghaemoglobin.
It is a  red-pigment that is filled outside the peribacteroid space in the cytosol of nodule cells. It has the ability to combine very rapidly with oxygen and thus acts a very efficient O₂ scavenger. 

 The correct order of arrangement of the given components from outside to inside in a woody dicot stem is as follows:
Phellem Secondary cortex Secondary phloem wood

TS of a typical dicot stem showing secondary growth

In a prokaryotic cell, nuclear envelope is not found. It means genetic material (DNA) is not enclosed by any envelope and lies in direct contact with the cytoplasm.

Fibrous joints are immovable joints in that occur between the bones of the cranium and in the tooth sockets. They do not allow movement because the bones are held firmly together by bundles of strong white collagen fibres. The immovable joints are often known as the sutures. The periosteum that covers the bones dips between them as a septum

The imperfect fungi which are decomposers of litter and help in mineral cycling belong to Deuteromycetes. They are fungi which do not fit into the commonly established taxonomic classification of fungi. They include all those fungi in which the perfect stage(sexual stage) is not reported. 

Chromatophores are found in members of phototrophic bacteria. They contain bacteriochlorophyll pigments and carotenoids and take part in photosynthesis. In purple bacteria, such as Rhodospirillum rubrum, the light-harvesting proteins are intrinsic to the chromatophore membranes. However, in green sulphur bacteria, they are arranged in specialised antenna complexes called chlorosomes. 

Aldosterone is not involved in sugar metabolism. It is a steroid hormone (mineralocorticoid) produced by the outer section(zona glomerulosa) of the adrenal cortex in the adrenal gland. It plays a central role in the adrenal gland. It plays a central role in the regulation of blood pressure mainly by acting on the distal tubules and collecting ducts of the nephron, increasing reabsorption of ions and water in the kidney, to cause the conservation of sodium, secretion of potassium, increase in water retention and decrease in blood pressure and blood volume. 

Production of body heat is the function of muscles. The contraction of muscle produce heat, which keeps the body warm during the winters. 

The grain of wheat, maize or rice is a caryopsis. The embryo in such grains lies laterally near the base of the grain. The embryo consists of an upper large, shield-shaped cotyledon known as scutellum. The scutellum is closely pressed against the endosperm and helps in the translocation of nutrients from endosperm to the growing embryo at the time of germination and seedling growth.