Tag: science & technology

The cell is the fundamental structural and functional unit of all living organisms. All life processes occur at the cellular level. Option A is correct. Genes, DNA, and RNA are molecules within cells but are not themselves the basic living unit - they are components that carry genetic information.

Pure distilled water has a pH of exactly 7, which is considered neutral on the pH scale (0-14). The pH scale measures acidity (below 7) and alkalinity (above 7). Option B is correct. A pH of 8 would be slightly basic, while 6 and 5 would be acidic.

Covalent bonds are the strongest chemical bonds among common types, involving the sharing of electron pairs between atoms. They have bond energies typically ranging from 150-400 kJ/mol. Option B is correct. Ionic bonds (C) are strong but generally weaker than covalent in similar conditions, while hydrogen bonds (A) and Van der Waals forces (D) are much weaker intermolecular forces.

Hubble's Law states that galaxies are moving away from each other at speeds proportional to their distance - this is the key evidence for an expanding universe. The law is expressed as v = H₀ × d, where v is recession velocity and d is distance. Option C is correct. It does not describe the speed of light (A), stellar rotation (B), or planetary orbits (D).

Sharks have skeletons made entirely of cartilage, a flexible connective tissue, rather than bone. This makes them lighter and more agile swimmers. Cartilaginous fish also include rays and skates. Option D is correct. Bones (A) are found in bony fish, while muscles (B) and tendons (C) are soft tissues, not skeletal structures.

Platelets (thrombocytes) are cell fragments responsible for blood clotting. They form plugs at injury sites and release clotting factors. Red blood cells transport oxygen, white blood cells fight infection, and lymph nodes are immune system organs - none of these handle clotting.

A hurricane is a rotating storm system with winds exceeding 75 mph (119 km/h). The term specifically refers to tropical cyclones in the Atlantic and Northeast Pacific. Tornadoes are different storm types, and 'cyclone' has regional naming conventions. 'Gustnado' is a smaller, short-lived phenomenon.

Hippos are the closest living relatives of whales among land mammals. Both belong to the order Artiodactyla (even-toed ungulates). Genetic and fossil evidence shows whales evolved from early artiodactyls, making hippos their nearest terrestrial cousins. Warthogs are also artiodactyls but more distant.

Proteins are present in every part of your body - muscles, organs, skin, hair, enzymes, hormones, and even bone matrix. They are structural components and functional molecules. Fat is stored in adipose tissue, starch comes from plants, and sugar is mainly in blood - they aren't everywhere.

The pituitary gland is called the 'master gland' because it produces hormones that regulate other endocrine glands like the thyroid, adrenal glands, and reproductive organs. The pineal gland regulates sleep cycles, the pancreas produces insulin and digestive enzymes, and while the brain controls everything, it's not typically called the 'master gland' in endocrine contexts.