Biology Demystified: A Self Teaching Guide
Format: PDF / Kindle (mobi) / ePub
Guide to understanding basic and applied scientific information, for those who've had not formal training in biology. Includes more than 150 illustrations, a pronunciation guide, self-tests, and reviews. Softcover. DLC: Biology.
and gulps air into its oral cavity. The next step is the one that creates a 3, Order positive-pressure breathing effect: the frog closes its nostrils and raises the floor of its mouth. This action creates a pushing force, thereby increasing the atmospheric pressure within the frog’s mouth. Inspiration occurs because air from the mouth is then pushed down through the pharynx and trachea, and into the lung alveoli, which have a lower pressure. NEGATIVE-PRESSURE BREATHING In contrast to
carcinogens may trigger abnormal changes (mutations) in the DNA of epithelial or connective tissue cells. The mutations create errors in the genetic program of the Cell Cycle, such that the resulting daughter cells are highly abnormal. The mutated, cancerous daughter cells [13:24 13/6/03 N:/4058 LAYMAN.751/4058-Alltext.3d] Ref: 4058 Layman: Biology Demystified All-text Page: 87 1-388 88 PART 2 Universal Building Blocks of Life have a largely unregulated, disorganized, and extremely
which contains the major viscera (VIH-ser-ah) or ‘‘guts’’ (internal organs). The coelom cavity is also found within the visceral mass. It holds the heart of the organism. The foot of the mollusk is the inferior portion of the visceral mass, which, somewhat like a human foot, is large and fleshy and flat. The foot pushes against the ground or sea bottom, propelling the mollusk forward. In addition to their basic body plan, many species of mollusks are classified as bivalves (BUY-valves). This is
myofilament.] The myosin cross-bridge is the chief contact point between the thin actin and thick myosin myofilaments. It is also vitally important because of its close functional relationship with the high-energy ATP molecule. You may remember (Chapter 4) that the ATP molecule is split by a special kind of enzyme, called ATPase. In the case of muscle, the enzyme is myosin ATPase. THE SLIDING FILAMENT THEORY According to the sliding filament theory of muscle contraction, muscles shorten
vesicle is literally a ‘‘tiny bladder’’ that consists of a membrane surrounding thousands of neurotransmitter (NUR-oh-trans-mit-er) molecules. Each time an action Dendrites Cell nucleus Axon Neuron cell body Action potential MOTOR NEURON Vesicles containing ACh molecules Neuromuscular junction (motor end plate) Axon terminal Transmitter binding sites SKELETAL MUSCLE FIBER Fig. 14.8 The neuromuscular junction and muscle excitation. [13:26 13/6/03 N:/4058