Biology Test - 35

Venation in monocots is parallel.

The phenomenon of the arrangement of veins on the leaf is called venation. There are two types of venation, namely reticulate venation and parallel venation. Reticulate venation involves the irregular distribution of veins to form a network. Examples of plants showing reticulate venation include rose, tulsi, hibiscus, papaya, ficus. Parallel venation involves the veins running parallel to each other. Examples of plants showing parallel venation include grains, banana, canna, grass, Musa. Leaves of monocot plants generally show parallel venation and leaves of dicot plants generally show reticulate venation.

P and Q are correct combination of statements on alkylating agents as antineoplastics.

An alkylating antineoplastic agent is an alkylating agent used in cancer treatment that attaches an alkyl group (C_nH_2n+1) to DNA. The alkyl group is attached to the guanine base of DNA, at the number 7 nitrogen atom of the purine ring. Since cancer cells, in general, proliferate faster and with less error-correcting than healthy cells, cancer cells are more sensitive to DNA damage such as being alkylated. So, they get converted to azindinium ions and bind to 7th position - N atom of guanine of DNA base pairs. So, P is correct.

Before their use in chemotherapy, alkylating agents were better known for their use as sulfur mustard, ("mustard gas") and related chemical weapons in World War I. The nitrogen mustards were the first alkylating agents used medically, as well as the first modern cancer chemotherapies.  Nitrogen mustards and Sulfur mustards belong to this class of drugs. So, Q is correct.

Decrease in death rate and Development of agriculture are the primary factors for population explosion.

Population explosion means a sudden increase in the number of individuals in a particular species. The term is used to refer to the world’s human population. In India, Population explosion has become a severe matter of concern because the increase in population leads to poverty and illiteracy. 

Lipid molecule in plasma membrane are arranged inHead parallel.

Lipid molecules in plasma membrane form a bilayer with hydrophobic tails buried inside the central region and hydrophilic ends towards the two surfaces. According to the fluid mosaic model of Singer and Nicolson, cell membranes are quasi-fluid in nature with a viscous lipid bilayer having proteins at places (mosaic) both on the surface and inside. The arrangement of lipids in bilayer is also called as a head parallel arrangement because the polar heads of both the lipid layers are oriented on the surface and hydrophilic tails are embedded towards the inside of the membrane.

The portion of apical meristem that gives rise to xylem tissue is called procambium.

The epidermis, primary xylem, primary phloem, pith and cortex are all produced by the apical meristem. The apical meristem after mitosis gives rise to three meristems. The secondary layer, which is made up of procambium gives rise to the primary xylem and primary phloem.

The correct option is (3) because
(a) Placenta secretes human chorionic gonadotropin (hCG)
(b) Zona pellucida is a primary egg membrane secreted by the secondary oocyte
(c) The secretions of bulbourethral glands help in lubrication of the penis
(d) Leydig cells synthesise and secrete testicular hormones called androgens

A genetically engineered micro-organism used successfully in bioremediation of oil spills is a species of Pseudomonas.

Pseudomonas is used in bioremediation owing to its aerobic metabolism with ability to degrade organic pollutants such as toluene and to convert styrene oil to biodegradable plastic Polyhydroxyalkanoates (PHA).

Robert Koch's postulates to establish a micro- organism as pathogen can be obtained, after his work on anthrax.

Robert Koch'spublication in \(1877\) on the structure of anthrax bacterium marked the first photography of a bacterium. He discovered the formation of spores in anthrax bacteria, which could remain dormant under specific conditions. However, under optimal conditions, the spores were activated and caused disease.

T Lymphocytes, B Lymphocytes,Dendritic cells and Natural killer cellscontribute for immune system.

• T lymphocytes, or T cells, are responsible for cell-mediated immunity. T cells come in many types with specific functions, including: Helper T cells direct the immune system.
• The B cell, or B lymphocyte, is an immunologically important cell. It is not thymus-dependent, has a short lifespan, and is responsible for the production of immunoglobulins. It expresses immunoglobulins on its surface.
• Dendritic cells ( DCs) are antigen-presenting cells (also known as accessory cells) of the mammalian immune system. Their main function is to process antigen material and present it on the cell surface to the T cells of the immune system. They act as messengers between the innate and the adaptive immune systems.
• Natural killer cells, also known as NK cells or large granular lymphocytes (LGL), are a type of cytotoxic lymphocyte critical to the innate immune system that belong to the rapidly expanding family of innate lymphoid cells (ILC) and represent 5–20% of all circulating lymphocytes in humans.

The packing tissues in plants that stores food, nutrients, and water are called Parenchyma. Parenchyma with chlorophyll is called chlorenchyma and parenchyma with air is called aerenchyma. The intercellular gaps in Parenchyma are large. Aerenchyma is mostly present in aquatic plants and chlorenchyma is present in leaves.