Biology (CDS-Solved Paper)

Roots are the main absorbing organ in plants. This underground part of plant, which absorbs water and soluble mineral salts from soil.

Conduction of food and water is not the primary function of a green leaf. Manufacture of food by photosynthesis, gaseous interchange by stomata and evaporation of water (Transpiration) are primary functions of leaves. Conduction of water and food is done by vascular tissues. Conduction of water occurs via xylem and conduction of food occurs via phloem.

True fruit develops from the ovary of flower after fertilisation, while false or pseudo fruit develops from other parts of flower, i.e. the edible part of apple is fleshy receptacle.

Guttation is special physiological process in which excess water escapes in the form of liquid droplets from the tips and margins of leaves. It occurs during night or early morning, when there is high atmospheric humidity and rate of transpiration is lower than the rate of water absorption.

Xylem is responsible for transportation of water and solutes (soluble mineral ions). Thus, its blocking will affect transportation of water and solutes.

Fungus does not contribute to propagation of plants through seed dispersal, other factors are helpful in seed dispersal. The dislocation of seeds from their parental plants by different mediums is known as seed dispersal. The seeds of Calotropis, Rafflesia and lotus are dispersed by wind, elephant and water, respectively.

Presence of eye on potato is an indication for modification of stem of a plant. Potato is a modified stem, known as tuber. The eye of potato is a very small axillary bud, which contains small internodes and nodes. It can give rise to a new plant via asexual reproduction.
The tendrils of pea and scales of onion are modification of leaves, while hairs on carrot are part of root.

Epididymis, vas deferens, seminal vesicles and prostate in male reproductive system of human are involved in maturation and motility of sperms. Spermatogenesis occurs in testes, which is a process of formation of sperms.

Colostrum is a type of milk produced by a lactating mother essential for development of immune response of newborn baby in human. It is the first yellow and thick milk produced by a lactating mother. It contains IgA antibodies in abundance, which are essential for the development of immune response against many diseases in a newborn baby.

RNA is relatively unstable compared to DNA, which explains higher mutation rate and faster evolution found in RNA virus. The main reasons of unstability of RNA are presence of 2OH group in ribose sugar makes RNA more labile and degradable because it is highly reactive group and single strand structure.