Biology:2012:CBSE:[All India]:Set-I

Parthenocarpic fruits are either seedless or contain non-viable seeds as in banana fruits. Hence, banana is considered a good example of parthenocarpy.

Two different roles of spleen in the human body are:

i) Mechanical filtration of blood as it contains lymphocytes and phagocytes.

The trait with respect production of axial white flowers is dominant over the trait responsible for production of terminal violet flowers.

Vehicles fitted with catalytic converters should use unleaded petrol because lead in the petrol inactivates the metal catalyst present in the converter.

Acrosome is a cap-like structure present in the anterior part of sperm head. It contains the enzyme hyaluronidase, which hydrolyses the outer egg membrane and thus it facilitates penetration of the egg at the time of fertilisation.

(a) Apis indica is the most common species of bee suitable for apiculture. 
(b) Leghorn or Minorca are the improved breeds of chicken

Wing of a cockroach and wing of a bird are analogous organs as their origin is not the same but they perform similar functions. From the above example one can infer the evolutionary relationship between organisms.

Cyanobacteria such as Anabaena and Nostoc, fix atmospheric nitrogen. They serve as important bio-fertilisers especially in paddy fields.

(a) Diagram of a nucleosome

(b) Histones are positively charged because they are rich in the basic amino acid residues lysine and arginine. These amino acids carry positive charges in their side chains.

Flowers which do not open at all are called cleistogamous flowers.

Advantage of cleistogamy:

Produce seed-set even in the absence of pollinators and thus cleistogamous plant can propagate itself even in the absence of pollinating agents.

Disadvantage of cleistogamy: