Automation

Automation, system of manufacture designed to extend the capacity of machines to perform certain tasks formerly done by humans, and to control sequences of operations without human intervention. The term automation has also been used to describe nonmanufacturing systems in which programmed or automatic devices can operate independently or nearly independently of human control. In the fields of communications, aviation, and astronautics, for example, such devices as automatic telephone switching equipment, automatic pilots, and automated guidance and control systems are used to perform various operations much faster or better than could be accomplished by humans.

Embryology

Embryology, branch of biology dealing with the development of the animal embryo. (For the embryology of plants, see Fertilization; Plant; Seed.) Embryology includes within its province the development of the fertilized egg and embryo and the growth of the fetus.

Comparative Embryology

Sea urchins, frogs, humans, and many other animals are remarkably similar in their early development. All begin with a single cell that divides into two cells, the first step in the process of cleavage (1a, 2a, 3a). During cleavage, cell divisions occur so rapidly that the cells do not have time to grow between divisions, and the result is smaller and smaller cells. Cleavage produces a solid ball of cells called a morula (1b, 2b, 3b). Within the morula, a fluid-filled cavity called the blastocoel develops, converting a morula into a blastula (1c, 2c, 3c). In a process called gastrulation, certain cells of the blastula migrate to different regions of the blastula to create the gastrula, a structure with three cell layers (1d, 2d, 3d). The outer cell layer of the gastrula, called the ectoderm (shown in blue), forms the outer covering of all animals, and in the frog, human, and other higher animals, it also forms the nervous system. The inner layer of the gastrula, known as the endoderm (shown in yellow), gives rise to the gut in all animals, and in higher animals, other organs including the stomach, pancreas, liver, and lungs. The mesoderm, which forms between the ectoderm and endoderm, produces the simple excretory system of the sea urchin and frogs and the kidneys of humans. In higher animals, the mesoderm also gives rise to blood, bone, muscle, and other structures. Cell specialization is followed by the development of primitive organs, which marks the larval form of sea urchins and frogs, and the embryo stage of human development (1e, 2e, 3e). Size and time of development vary widely among species. The sea urchin larva, for example, forms in 12 to 76 hours and measures 0.1 to 0.3 mm (0.004 to 0.01 in), while the human embryo takes eight weeks to fully form, and measures about 30 mm (about 1.2 in) from crown to rump.

Physiology

Physiology, study of the physical and chemical processes that take place in living organisms during the performance of life functions. It is concerned with such basic activities as reproduction, growth, metabolism, excitation, and contraction as they are carried out within the fine structure, the cells, tissues, organs, and organ systems of the body.

Physiology is intimately linked with anatomy and was historically considered a part of medicine. Its emphasis on investigating biological mechanisms with the tools of physics and chemistry made physiology a distinct discipline in the 19th century; the tendency today, however, is toward a fragmentation and merging with the many specialized branches of the life sciences. Three broad divisions are recognized: general physiology, concerned with basic processes common to all life forms; the physiology and functional anatomy of humans and other animals, including pathology and comparative studies; and plant physiology, which includes photosynthesis and other processes pertinent to plant life.

The first studies in animal physiology were probably undertaken about 300 bc by the Alexandrian physician Herophilus, who reportedly vivisected the bodies of criminals. For about 1900 years thereafter, few physiological studies were performed.

Modern animal physiology dates from the discovery of the circulation of the blood by the English physician William Harvey in 1616. Shortly thereafter, the Flemish chemist Jan Baptista van Helmont developed the concept of gases and suggested the use of alkalies in treating digestive disturbances; the Italian biophysicist Giovanni Alfonso Borelli published studies of animal motion, suggesting that the basis of muscle contraction lay in the muscle fibers; the Dutch microscopist Antoni van Leeuwenhoek gave the first descriptions of red blood cells and spermatozoa; and the Italian histologist Marcello Malpighi demonstrated the existence of capillaries and studied the physiology of the kidney, liver, and spleen. During the second half of the century the study of glands was initiated by the English physician Thomas Wharton, who demonstrated salivary secretion, and by the Danish anatomist Nicolaus Steno, who demonstrated the secretions of the tear glands and salivary glands. The Dutch physician Regnier de Graaf furthered glandular study by his discovery of the follicles in the ovary; he also performed studies on pancreatic juices and bile. The English physician Richard Lower was the first to transfuse blood (see Blood Tansfusion) from one animal to another, and the French physician Jean Baptiste Denis first gave a human being a successful blood transfusion.

Genetic Engineering

Genetic Engineering, alteration of an organism's genetic, or hereditary, material to eliminate undesirable characteristics or to produce desirable new ones. Genetic engineering is used to increase plant and animal food production; to help dispose of industrial wastes; and to diagnose disease, improve medical treatment, and produce vaccines and other useful drugs. Included in genetic engineering techniques are the selective breeding of plants and animals, hybridization (reproduction between different strains or species), and recombinant deoxyribonucleic acid (DNA).

Genetic engineering enables scientists to produce clones of cells or organisms that contain the same genes.

1. Scientists use restriction enzymes to isolate a segment of deoxyribonucleic acid (DNA) that contains a gene of interest—for example, the gene regulating insulin production.
2. A plasmid removed from a bacterium and treated with the same restriction enzyme binds with the DNA fragment to form a hybrid plasma.
3. The hybrid plasmid is re-inserted back into the bacterium, where it replicates as part of the cell’s DNA.
4. A large number of identical daughter cells (clones) can be cultured and their gene products extracted for human use.

Biochemistry

Biochemistry, study of the substances found in living organisms, and of the chemical reactions underlying life processes. This science is a branch of both chemistry and biology; the prefix bio- comes from bios, the Greek word for “life.” The chief goal of biochemistry is to understand the structure and behavior of biomolecules. These are the carbon-containing compounds that make up the various parts of the living cell and carry out the chemical reactions that enable it to grow, maintain and reproduce itself, and use and store energy.

A vast array of biomolecules is present in the cell. The structure of each biomolecule determines in what chemical reactions it is able to participate, and hence what role it plays in the cell's life processes. Among the most important classes of biomolecules are nucleic acids, proteins, carbohydrates, and lipids.

Nucleic acids are responsible for storing and transferring genetic information. They are enormous molecules made up of long strands of subunits, called bases, that are arranged in a precise sequence. These are “read” by other components of the cell and used as a guide in making proteins.

Proteins (see Protein) are large molecules built up of small subunits called amino acids. Using only 20 different amino acids, a cell constructs thousands of different proteins, each of which has a highly specialized role in the cell. The proteins of greatest interest to biochemists are the enzymes, which are the “worker” molecules of the cell. These enzymes serve as promoters, or catalysts, of chemical reactions.

Carbohydrates are the basic fuel molecules of the cell. They contain carbon, hydrogen, and oxygen in approximately equal amounts. Green plants and some bacteria use a process known as photosynthesis to make simple carbohydrates (sugars) from carbon dioxide, water, and sunlight. Animals, however, obtain their carbohydrates from foods. Once a cell possesses carbohydrates, it may break them down to yield chemical energy or use them as raw material to produce other biomolecules.

Lipids are fatty substances that play a variety of roles in the cell. Some are held in storage for use as high-energy fuel; others serve as essential components of the cell membrane.

Biomolecules of many other types are also found in cells. These compounds perform such diverse duties as transporting energy from one location in the cell to another, harnessing the energy of sunlight to drive chemical reactions, and serving as helper molecules (cofactors) for enzyme action. All these biomolecules, and the cell itself, are in a state of constant change. In fact, a cell cannot maintain its health unless it is continually forming and breaking down proteins, carbohydrates, and lipids; repairing damaged nucleic acids; and using and storing energy. These active, energy-linked processes of change are collectively called metabolism. One major aim of biochemistry is to understand metabolism well enough to predict and control changes that occur in cells. Biochemical studies have yielded such benefits as treatments for many metabolic diseases, antibiotics to combat bacteria, and methods to boost industrial and agricultural productivity. These advances have been augmented in recent years by the use of genetic engineering techniques.