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

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" »

Understanding the Human Genome

The study of the human genome involves understanding the complete set of DNA molecules organized into 23 chromosomes. To fully comprehend the information it contains, we must know the sequence of its bases. This knowledge has been instrumental in identifying the human genome. To grasp its immense scale, imagine a library 18 stories high. Current research focuses on deciphering the function of individual genes and how they interact to govern the organization and functioning of the human body.

Benefits of Human Genome Knowledge

Knowing the human genome offers significant advantages. Primarily, it accelerates the identification of disease-causing genes and helps identify individuals who are carriers of diseases. Understanding... Continue reading "Decoding the Human Genome: DNA, Disease, and Future Health" »

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

Animal Sensory Organs

The Lateral Line System

The lateral line is a specialized sensory organ found in fish and amphibian larvae. It can be identified as longitudinal lines on each side of the animal's body. These lines are formed by a succession of small pores that cross the scales and connect with a long, fluid-filled tube running beneath the skin along the animal's flanks. The inner tube is lined with hair cells, capable of capturing even the smallest water vibrations.

Facial Pits

The facial pit is a thermosensitive organ found in some snakes, such as rattlesnakes. It consists of two structures located between the eyes and mouth. These pits contain receptors capable of capturing infrared radiation, i.e., the heat emitted by other bodies. This... Continue reading "Animal Adaptations: Sensory Organs and Protective Structures" »

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