Biology MCQs

Notes:
Blood is considered a connective tissue for two basic reasons:
(i) embryologically, it has the same origin (mesodermal) as do the other connective tissue types and
(ii) blood connects the body systems together bringing the needed oxygen, nutrients, hormones and other signaling molecules, and removing the wastes.

Notes:
Gastric acid, also known as gastric juice or stomach acid, is a digestive fluid, formed in the stomach. It is composed of hydrochloric acid (HCl), potassium chloride (KCl) and sodium chloride (NaCl). It is strongly acidic with pH varying from 1.5 to 3.5. the acid plays a key role in digestion of proteins.

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:
Palynology is the scientific discipline concerned with the study of plant pollen, spores, and certain microscopic planktonic organisms, by this way diatom, in both living and fossil form. It is associated with the plant sciences as well as with the geologic sciences, notably those aspects dealing with stratigraphy, historical geology, study of organic microfossils (palynomorphs) extracted from ancient coals, paleontology and archaeology.

Notes:
The thin layer of living cells just inside the bark is called the cambium. It is found in the area between xylem and phloem. It forms parallel rows of cells, which result in secondary tissues. It is the part of the tree that makes new cells, allowing the trees to grow wider each year.

Notes:
Enzymes are sometimes called biological catalysts because they speed up reactions, and only small amounts are required. Digestive enzymes speed up the breakdown of complex food substances into simpler subunits. The breakdown of food in digestion is actually caused by water chemically splitting the complex food molecules, a process called hydrolysis.

Notes:
It was discovered relatively long ago (1930’s) that injections of progesterone (pregnancy hormone) were effective as a contraceptive in preventing pregnancies. Progesterone is used as a contraceptive for creating a hostile environment for fertilization and not allowing sperm to enter the egg.

Notes:
Most species of Euglena have photosynthesizing chloroplasts within the body of the cell, which enable them to feed by autotrophy (making energy-containing organic molecules from inorganic raw material through the use of an energy source such as sunlight), like plants. However, they can also take nourishment heterotrophically (making use of food that comes from other organisms in the form of fats, carbohydrates, and proteins), like animals. So Euglena have features of both animals and plants.

Notes:
A plant’s life span begins with its germination and continues still it bears a fruit and eventually dies off. All this happens in a season or two or more. Hence, plants are classified into three types based on life cycle they have, namely : Annuals, Biennials, Perennials.

Notes:
Time required for the organism to eliminate 50 per cent of the total body burden or tissue concentration of chemical is referred to as Half Life Period. A biological half-life or elimination half-life is the time it takes for a substance (drug, radioactive nuclide, or other) to lose one-half of its pharmacologic, physiologic, or radiological activity.