Biology MCQs

Notes:
Humming birds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm (3–5 in) range. Indeed, the smallest extinct bird species is a humming bird, the 5-cm Bee Humming bird. These birds being the smallest are, capable of flying both in forward and back direction.

Notes:
Changes in pH which can accompany metabolic process such as respiration (aerobic glycolysis for example) can alter the conformation of an enzyme and hence enzyme activity such as salivarya mylase is effective in neutral condition, pepsin in acidic condition l.5 (less than pH 7) and trypsin in basic condition (more than pH 7).

Notes:
Blood group AB individuals are universally known as recipients because they can receive blood from any group, this is due to the presence of both A and B antigens on the surface of their RBC’s and an absence of antibodies against either A or B antigen in the plasma. However, they can only donate blood to individuals of the same AB blood group.

Notes:
The color of normal urine is usually light yellow to amber. Generally, the greater the solute volume the deeper the color. The yellow color of urine is due to the presence of a yellow pigment, urochrome. Deviations from normal color can be caused by certain drugs and various vegetables such as carrots, beets, and rhubarb.

Notes:
Interferons (IFNs) are a group of signaling proteins made and released by host cells in response to the presence of pathogens, such as viruses, bacteria, parasites, or tumor cells. Interferon synthesis occurs primarily in response to viral single-stranded or double stranded RNA that are either the genetic material of RNA viruses or a product of viral transcription. Interferons are named for their ability to “interfere” with viral replication by protecting cells from virus infections.

Notes:
Plague is caused by bacteria. It is a deadly infectious disease caused by the enterobacteria Yersinia pestis, named after the French-Swiss bacteriologist Alexander Yersin. It has led to death of million of people at one time.

Notes:
In citrus fruits such as oranges, the nucleus cells that surround the embryo start dividing and protrude into the embryo sac. These develop into embryos; thus resulting in the presence of more than one embryo inside each ovule. This condition is known as polyembryony.

Notes:
The ‘unicellular organisms’ are single-celled organisms, wherein various functions like feeding, locomotion, expelling wastes, reproduction, etc. are carried out by the single cell. Some examples include organisms such as amoeba, euglena, paramecium, bacteria, and cyanobacteria. Hence, all options are correct as they all represent examples of unicellular organisms.

Notes:
A bee sting is strictly a sting from a bee (honey bee, bumblebee, sweat bee, etc.). Bee venom is acidic containing methanoic acid (HCOOH). Neutralizing a sting is unlikely to be effective as the venom is injected under the skin and deep into the tissues, where a topically applied alkali is unable to reach, so neutralization is unlikely to occur.

Notes:
An increase in the oxygen concentration in many plants results in a decrease in the rate of photosynthesis. This phenomenon of the inhibition of photosynthesis by O2 was first discovered by a German biochemist Warburg in 1920 in Chorella (a green alga) and is called Warburg effect. O2 causes greatest inhibition of photosynthesis when CO2 levels are low and light levels are saturating. This effect is known to occur in C3 plants (Soybean) and C4 plants (Sorghum, Maize, Sugarcane), etc.