Biology MCQs

Notes:
Oxygen is a natural element which no animal can live without. Fish and other aquatic animals depend on oxygen gas dissolved in water as much as people depend on oxygen gas in air. Many people are surprised to learn that fish and other aquatic organisms don’t use oxygen from water molecules (H2O). This is because the single oxygen molecule (O) is bound to the two hydrogen molecules (H2) and is not useable in this form. Instead, aquatic organisms depend on dissolved oxygen gas (O2), a colorless, tasteless and odorless substance that enters the water from plants and the atmosphere.

Notes:
The hypothalamus in the brain controls body temperature by regulating heat production and loss:
Temperature comparison: The hypothalamus compares the body’s current temperature to the normal temperature of around 37°C.
Heat production: If the body is too cold, the hypothalamus triggers heat production.
Heat loss: If the body is too hot, the hypothalamus triggers heat loss, such as sweating or giving off heat.

Notes:
The word latex means only natural rubber. Natural rubber is made from the white sap of some trees such as the Hevea brasiliensis (Euphorbiaceae). Other elastomers, called synthetic rubbers, are made by chemical processes.

Notes:
• Apoptosis is the process of programmed cell death in multicellular organisms. Apoptosis occurs during normal cell turnover, development and in immune system.
• Ageing is the accumulation of changes.
• Degeneration is the deterioration of a tissue or an organ in which its function is diminished or its structure impaired.
• Necrosis is the disorganized break down of flesh in some part of the body of multicellular organism.

Notes:
Complementary base pairing in the DNA double helix (with its complementary DNA strands) describes the manner in which deoxyribose- nucleotides bind to each other. Essentially it means that the bases are arranged along the molecule such that the chains fit together snugly so as to be lightly secured by hydrogen bonds.

Notes:
This virus is spread by mosquito bites and has become an important cause of viral meningitis in most of the United States.
Bacterial meningitis symptoms may develop within hoursor days. Fever, severe headache, and neck stiffness are the hallmark symptoms of meningitis. Others include: Nausea and vomiting.
 

Notes:
β-oxidation in mammals occurs in both mitochondria and peroxisomes, whereas plants and most fungi switch off β-oxidation.

Notes:
According to Chargaff’s laws, the amount of adenine is always equal to that of thymine, and the amount of guanine is always equal to that of cytosine, i.e. A = T(120) and G = C (120), hence, the total no. The number of nucleotides would be 120 x 4 = 480.

Notes:
The Caliciviridae family contains five genera are Norovirus, Sapovirus, Lagovirus, Vesivirus, and Nebovirus.

Notes:
Lactobacillus bucheri is a naturally occurring, lactic acid bacteria that has a crucial role in forage preservation. It’s associated with indirect silage fermentation, which results in the production of acetic acid that inhibits yeast, prevents heating, and extends the bunk life of silage. Other species like Lactobacillus cacao num and Lactobacillus casei do not exhibit this function and Monosodium Glutamate is a flavor enhancer, not a preservative.