Biology MCQs

Notes:
The Stomata in the aquatic plants is found and available on upper surface only. Stomata are crucial for plant functioning as they play fundamental role in the regulation of gas exchange between the plant and its surrounding environment.

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Posterior region of skull is the right location of foramen magnum. The foramen magnum refers to a large oval opening (foramen) in the occipital bone of the skull in humans and as well as many other animals.

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The cells membranes hold enzymes of sequential reactions in close proximity

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The term Elasmobranches is a collective name for the sharks, skates and rays. Elasmobranches have a skeleton made of cartilage, no swim bladders and rough skin made up of small dermal dentils. Elasmobranches are renowned for their highly tuned senses.

Notes:
Drugs that bind to receptor sites and inhibit their natural function are called antagonists. These drugs are useful when a message needs to be blocked.
Antagonists bind to receptors but do not activate them. They compete with available agonists for receptor binding sites. Antagonists block the access or attachment of the body’s natural agonists, usually neurotransmitters, to their receptors. This prevents or reduces cell responses to natural agonists.
Antagonists still cause a response, but this is through blocking the actions of agonists.
Agonist and antagonist drugs can be used together in people with asthma. For example, albuterol can be used with ipratropium.

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A Xerophyte is a species of plant that has adapted to survive in an environment with little liquid water, such as a desert or an ice- or snow-covered region in the Alps or the Arctic.

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The discovery in 1953 of the double helix, the twisted-ladder structure of deoxyribonucleic acid (DNA), by James Watson and Francis Crick marked a milestone in the history of science and gave rise to modern molecular biology, which is largely concerned with understanding how genes control the chemical processes.

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Darwin’s theory of evolution can be described as: within any population, there is natural variation. Some individuals have more favourable variations than others. Even though all species produce a large number of offsprings, populations remain fairly constant naturally. The struggle for survival within populations eliminates the unfit individuals. This is called natural selection.

Notes:
Protoxylem is the first part of the primary xylem that matures and these cells are usually smaller than the metaxylem. Metaxylem is the part of the primary xylem that differentiates after the protoxylem and these cells are usually larger than the protoxylem.

Notes:
The vocal cord in women is about 15 mm long; in men vocal cords are about 20 mm long and children have very short vocal cords.