Biology (CDS-Solved Paper)

Endoplasmic reticulum has two types–Smooth Endoplasmic Reticulum (SER) and Rough Endoplasmic Reticulum (RER). SER have smooth surface due to lack of ribosomes. Thus, they do not help in protein synthesis unlike RER which contain ribosomes (the site of protein synthesis). SER help in synthesis of steroid hormones and lipids. They also form vesicles for the transportation of materials.

Lysosomes are called storehouse of digestive enzymes. These are single membrane bound cell organelles which contain various digestive or hydrolytic enzymes. Due to the presence of hydrolytic enzymes these are also called as suicidal bags of cell. These enzymes take part in hydrolysis of extracellular materials.

The lateral meristem tissues are responsible for increase of girth in the stem of a plant. This tissue is present along the side of organs, e.g. vascular cambium and cork cambium, which are responsible for the secondary growth of plants. Due to this secondary growth the girth of stems and roots increases.

Agaricus is an organism which is dependant on saprophytic mode of nutrition. They obtain their nutrition from dead and decaying organic matter. Rest organisms, i.e. Ulothrix, Riccia and Cladophora have autotrophic mode of nutrition.

Statement in option (b) regarding histone protein is correct. These are protein that are present in nucleus in association with DNA.

Haemoglobin of RBCs can carry both oxygen and carbon dioxide and it not used for clotting of blood. Hence, option (b) is the correct answer.

The correct sequence of passage of light in a compound microscope is condenser−Objective lens−Body tube-Eye piece. Compound microscope is a common light microscope usually used in labs of schools and colleges.

In this type of microscope, light reflected by mirror goes to condenser which condense light on object. From here, light goes to objective lens, body tube and eye piece, respectively.

The statement given in option (a) is correct, i.e. urea is produced in liver. As a result of metabolism of nitrogenous compounds (amino acids, proteins, nucleic acids), ammonia is produced. It combines with CO₂ through ornithine cycle and forms urea.

Nereis is a member of phylum–Annelida, which has bilateral symmetry in its body organisation. In bilateral symmetry, a lengthwise vertical plane divided the animals into two equal and opposite halves. Sea anemone of phylum–Cnidaria and Asterias and Echinus of phylum–Echinodermata have radial symmetry.

Peacock and camel are warm-blooded animals. These animals regulate their body temperature in any kind of environment. On the other hand, crocodile, hagfish, dogfish, tortoise are cold-blooded animals.