Notes, summaries, assignments, exams, and problems for Biology

The Skeletal System: Bones and Structure

Axial Skeleton

Vertebral Column

The vertebral column, or spine, holds the skull, attaches to the ribs, protects the spinal cord, and allows for the insertion of a large number of muscles. It consists of:

• Cervical vertebrae
• Thoracic vertebrae
• Lumbar vertebrae
• Sacrum
• Coccyx

Thoracic Cage

The thoracic cage includes the ribs and sternum.

• Ribs:
  • True ribs (first 7 pairs) join directly to the sternum.
  • False ribs (next 3 pairs) join the sternum indirectly via cartilage.
  • Floating ribs (last 2 pairs) do not join the sternum.
• Sternum: Composed of 3 parts:
  • Manubrium
  • Body
  • Xiphoid process

Appendicular Skeleton

The appendicular skeleton comprises the bones of the limbs and their girdles.

• Upper Extremities:
  • Girdle: Clavicles and scapulae
  • Arm:

The Organs of Speech

The Lungs

The lungs hold air when we breathe in. We enlarge the chest cavity (in part by lowering the diaphragm). This, in turn, expands the lungs, and air rushes in to fill the vacuum. Breathing out involves the opposite procedure. The chest is contracted, and air is squeezed out of the lungs, passing through the two bronchi (or bronchial tubes), then through the windpipe (more technically the trachea), and finally emerging in the throat.

The Larynx

Before the air reaches the throat, it has to pass through one of the most important speech organs: the larynx. It is at this point that the first possibilities occur for modifying the airstream and generating sound.

The larynx can conveniently be thought of as an irregularly shaped... Continue reading "The Organs of Speech and Sound Production" »

Animal Respiration Methods

1. Cutaneous Respiration (Skin)

Many small, less active multicellular animals respire through their skin. This is possible because the ratio between body surface area and body mass is very large. In larger, more active animals, it is sometimes a complementary method. This occurs in amphibians, where cutaneous respiration supplements lung respiration. In amphibians, gas exchange can be performed through the skin because it is well-vascularized and has large glands that keep it very moist. In some fish, skin breathing can occur via the oral mucosa, intestine, swim bladder, or the epidermis of the fins.

2. Gill Respiration

This is characteristic of aquatic animals. In this type of breathing, gas exchange takes place in the... Continue reading "Animal Respiration Methods Explained" »

Foods Discouraged

• Kitchen and table salt: salt, iodized salt, sea salt, celery salt.
• Meat: salted, smoked and cured.
• Smoked and dried fish, caviar.
• Sausages in general.
• Cheeses in general (Burgos types are allowed, Villalon).
• Bread and biscuits with salt (except for minor amounts of 50 g).
• Olives.
• Soup, instant mashed, diced, chips.
• Packaged vegetable juice.
• Oleaginous fruits, salty.
• Confectionery industry.
• Salted butter, margarine and salt.
• Sparkling water, carbonated beverages in general.
• Seasonings: salt, mustard, pickles, ketchup, meat tenderizer.
• Preserved foods in general.

Foods Allowed

• Meat, poultry.
• Viscera: tongue, kidneys, liver.
• Fresh fish freshwater or sea.
• Eggs.
• Milk, yogurt, Petit-suisse, curd.
• Cheese without salt.
• Unsalted bread and biscuits (up to

Larrel: The Root Structure

Larrel is a structure that has the dual mission to fix the plant in the soil and absorb water and mineral salts. In some cases, it serves as a reserve substance.

Parts of Larrel

They are morphologically and functionally different:

• Zone of Growth

  Formed by meristematic tissue, the apex is protected by the calyptra, composed of dead cells.

• Zone of Elongation

  Meristematic cells are transformed to become adult tissues. Elongation of cells is responsible for growth in length of the root.

• Piliferous Zone

  This is the closest to the stem. Here are found absorbent hairs.

Layers of Cells in Larrel

• The Cortical Cylinder

  • Epidermis: Its cells are absorptive hairs.
  • Cortical Parenchyma: Cells in which the plant stores food.
  • Endodermis: A monolayer

Activation Energy and the Activated Complex

Chemical reactions involve the breaking of some bonds in the reactants and the formation of new ones, resulting in specific products. For this to happen, a certain amount of energy, *q*, is required to activate the reactants. This energy is called activation energy and is necessary to initiate the reaction.

Molecules reach a higher-energy activated state or transition state where the bonds are partially broken. Because this reaction takes place, the products obtained are in a lower energy state. The higher the activation energy, the more difficult it will be to reach the activated state, and the reaction rate will be lower. One way to initiate the reaction is by heating the substance; the molecules... Continue reading "Activation Energy & Enzymes in Chemical Reactions" »

Basic Development Models

Protostomes

Protostomes: In protostomes, which translates to "mouth first", the mouth of the new individual develops separately from the blastopore, the first opening of the embryo.

Deuterostomes

Deuterostomes: In deuterostomes, which translates to "mouth second", the mouth opens later in a different place than the blastopore.

Extraembryonic Membranes

Extraembryonic membranes originate from the embryo but are not part of it. They form with input from all embryonic layers and play important roles in development:

• Yolk Sac: The first embryonic membrane that forms. It surrounds the mass of yolk, where one exists.
• Amnion: A membrane surrounding the embryo that secretes amniotic fluid, providing an aqueous environment.
• Chorion: Surrounds

Heart Muscle Contraction: How Does the Pacemaker Work?

The heart muscle consists of sarcomeres containing alternating thick and thin filaments. The cells tend to contract rhythmically and spontaneously, but these contractions are synchronized by electrical signals produced by specialized muscle fibers of the sinoatrial node. Cardiac muscle fibers are electrically interconnected by links between cells located interspersed. This allows for coordinated contraction. Specialized fibers act as a pacemaker. Action potentials that originate in the pacemaker spread quickly through the heart using specialized areas in which interspersed links connect adjacent muscle cell membranes. These allow the potential to synchronize their contractions as they travel... Continue reading "Heart Muscle Contraction, Lymphatic & Circulatory Systems in Animals" »

Trachea

Trachea are elongated cells, with thick walls and lose their cytoplasm at maturity, so they are dead cells. The terminal walls dissolve and form continuous tubes called vessels.

Sieve Tube

These cells are at the end to end and form long sieve tubes. Polyhedral cells of epithelium lining the trachea have cilia that beat synchronously to move substances.

DNSO

The fibers are arranged in different directions and at different levels, allowing them to endure stretching in all directions.

Internal Environment

Unicellular organisms trade directly with the extracellular environment they live in, while multicellular organisms rely on an internal environment as an intermediary between the external and intracellular environments.

Benefits

• Cells provide