Biology MCQs

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The components of blood include plasma, red blood cells and white blood cells, and cell fragments called platelets. The primary function of platelets is to aid in the blood clotting process. When activated, these cells adhere to one another to block the flow of blood from damaged blood vessels.

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Muscle fatigue refers to the decline in muscle force generated over sustained periods of activity. Intracellular acidosis due mainly to lactic acid accumulation has been regarded as the most important cause of skeletal muscle fatigue. Lactic acid accumulation leads to increased intracellular hydrogen ion (H+) concentration that leads to a weaker contraction.

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A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The pulmonary arteries are unique in that unlike most arteries which carry oxygenated blood to other parts of the body, the pulmonary arteries carry de-oxygenated blood to the lungs. After picking up oxygen, the oxygen rich blood is returned to the heart via the pulmonary veins.

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In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure. In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. The chromosome holds not only the genetic code, but many of the proteins responsible for helping express it.

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Frogs that spend the coldest times of the year inside of the mud or within rotten heaps of leaves during hibernation receive their necessary oxygen through their skin. This is referred to as cutaneous gas exchange. They use their skin to soak in the oxygen their bodies require. Outside of hibernation period, frogs usually respire using their lungs.

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Oxytocin is a hormone that is normally produced in the hypothalamus and stored in the posterior pituitary gland. It plays a role in social bonding, sexual reproduction in both sexes, and during and after childbirth. It’s released causes stretching of the cervix and uterus during labor and with stimulation of the nipples for breast feeding.

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Insect and bird wings are analogous structures but not homologous structures. They are externally similar in appearance and function (i.e. for flying), but have dissimilar origin and developmental plan.

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There are two types of squamous epithelium— simple squamous epithelium and stratified squamous epithelium. Simple squamous epithelium lines the blood vessels or alveoli in lungs. where transportation of substances occurs through selectively permeable membrane. It is made up of extremely thin and simple flat cells that form a delicate lining.

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The human heart is an organ that pumps blood throughout the body via the circulatory system, supplying oxygen and nutrients to the tissues and removing carbon dioxide and other wastes. The human heart has four chambers: two upper chambers (the atria) and two lower ones (the ventricles).

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An ecological pyramid is a graphical representation designed to show the biomass or bio productivity at each trophic level in a given ecosystem. Biomass is the amount of living or organic matter present in an organism. There are three ways to represent the trophic levels in an ecological pyramid:

1. the amount of organisms (number)
2. the mass of all the organisms in each level (biomass)
3. the amount of energy contained in each level.