Notes, summaries, assignments, exams, and exercises for Biology for Other courses

Mollusca Characteristics

Mollusks are triploblastic animals with true tissues. The body is typically divided into three main regions: head, foot, and visceral mass. When present, a calcareous shell protects the visceral mass and is secreted by the mantle. Mollusks have well-developed digestive, respiratory, circulatory, excretory, muscular and nervous systems.

Major Classes of Mollusca

• Gastropoda — snails and slugs (found in many environments).
• Cephalopoda — octopuses, squids and nautiluses (primarily marine).
• Bivalvia — clams, mussels and oysters (freshwater and marine).

Digestive System

Most mollusks feed using a radula (a rasping tongue with chitinous teeth) that scrapes or tears food. Bivalves are an exception: they are filter feeders and...

The Fate of Organic Matter in Plants

Metabolism is the result of the interaction between two types of processes: anabolism and catabolism.

Anabolism and Photosynthesis

Anabolism in plants groups all chemical reactions in which complex substances are produced from other simpler ones. The primary anabolic process carried out by plants is photosynthesis. However, plants also perform other anabolic processes, so that the substances produced during photosynthesis build their own structures or are used as reserve substances synthesized through these processes, such as starch, cellulose, and proteins.

Starch is the primary reserve substance in plants. It is formed from simple sugars in a reversible reaction that is reversed when the plant needs glucose....

Fundamentals of Nutrition and Metabolism

Defining Key Biological Concepts

Nutrition: The set of processes by which living things incorporate foreign substances to obtain matter and energy.

Food (Alimentos): Substances consumed by living beings.

Feeding (Alimentación): The process of taking food. Food is composed of substances called nutrients.

Types of Nutrition

Nutrition is classified based on how organisms obtain organic matter:

• Autotrophs

  Capable of producing their own organic matter from simple inorganic substances. They require an energy source:

  • Photosynthetic: Obtain energy from sunlight (e.g., algae, plants, and photosynthetic bacteria).
  • Chemosynthetic: Use energy released by specific chemical reactions (e.g., determined bacteria).

• Heterotrophs

  Use

Bacterial Pathogens and Clinical Characteristics

Streptococcus pyogenes

• Features: Gram-positive, unmovable, capsules, protamine, hemolysate, hyaluronic acid, disseminated erythrogenic toxin (scarlet fever), alpha-Dick, endocardial, anti-streptolysin O ("A").
• Treatment: Penicillin.

Streptococcus pneumoniae

• Features: Gram-positive, negative capsules, causes pneumonia, sinusitis, meningitis. Blood agar culture, optochin, bile solubility, Quellung reaction.
• Treatment: Penicillin.

Mycobacterium tuberculosis

• Features: Ziehl-Neelsen stain, strictly aerobic, intracellular, cord factor, niacin positive, Löwenstein-Jensen medium. Tuberculosis: susceptible, Mantoux test positive (current).

Staphylococcus aureus

• Features: Gram-positive, facultative anaerobic, food

Surgical Enterostomies

Gastrostomy Procedure

For temporary access, a Foley catheter is placed through the abdominal wall into the stomach. The balloon at its end is inflated inside the stomach to secure the tube. Gastrostomy can be used for a long time, with less danger and inconvenience than nasogastric tubes. Complications arise when the tube is dislodged, skin erosion occurs, or there is leakage of gastric contents or formula, causing local infection or peritonitis.

Jejunostomy Procedure

Jejunostomy involves creating a jejunal loop brought to the abdominal wall and inserting a tube into the jejunum through the wall. Surgical jejunostomy also achieves the same reduction in aspiration risk as nasojejunal feeding and less frequently causes erosion...

Ecological Succession: Ecosystem Transformation

Ecological succession is the sequence of changes that occur in an ecosystem, resulting from its own internal dynamics. It is a slow and gradual process, leading to the evolution of an ecosystem from an initial state of low biological diversity towards a final state of greater diversity.

General Changes in Succession Sequences

In all ecosystems, as the succession sequence progresses, the following phenomena generally occur:

• Increased species diversity
• Increased structural complexity
• Increased biomass
• Increased efficiency in energy use
• Lower net productivity (as more energy is used for maintenance)
• Increased ecosystem stability

The Climax Community Concept

The climax community is considered the ideal state...

Artificial Immunity

Artificial immunity involves administering substances to help the body overcome pathogenic infections.

a) Active Immunity or Vaccination

This involves the administration of a preparation (vaccine) containing specific antigens that trigger a primary immune response, providing protection against disease. Pathogens are often inactivated or weakened, or toxins are neutralized. To avoid dangerous reactions, modern vaccines are made with pure surface proteins or antigens. Vaccination is a highly effective preventive measure, though its effects vary in duration. It is not effective once the body is already infected.

b) Passive Immunity or Serum Therapy

This involves the injection of purified antibodies. It is used when an infection...

Exception to the Cell Theory: Viruses

Is a self-replicating biological entity capable of using cellular machinery. It is a potentially pathogenic agent composed of a capsid protein surrounding the nucleic acid, which can be DNA or RNA. This structure can, in turn, be surrounded by the viral envelope, a lipid layer with different proteins, depending on the virus's life cycle. A virus always needs the metabolic machinery of an invaded cell to replicate its genetic material, producing many copies of the original. This process underlies the destructive power of viruses because they can damage or destroy the cell.

Features of Viruses:

• Size: Extremely small.
• Crystallization Structure: Having a volume and identical form, viral particulates tend to order

Meiosis and Cell Division Stages

First Meiotic Division (Meiosis I)

• Diplotene: This stage starts by separating each homologous pair. The two chromatids become visible, the synaptonemal complex disappears, and chromosomes condense. Although separate, homologs remain united by chiasmata; these bivalents are called tetrads.
• Diakinesis: Continuous shortening and widening of the chromosomes, maintaining the aspect of tetrads.
• Metaphase I: Tetrads are located at the equatorial plate. The chiasmata shorten, separating the homologous chromosomes, but the centromeres do not split, and sister chromatids do not separate.
• Anaphase I: Chiasmata are broken, and each homologous chromosome moves to opposite poles.
• Telophase I: The nuclear envelope regenerates, and

Bacterial Characteristics & Cell Shapes

Bacteria are prokaryotic cellular organisms. Their structure is very simple and lacks a nucleus. Most bacteria, with the exception of mycoplasmas, have a cell wall that is more or less rigid, but with a very diverse structure and chemical composition, different from those of plants. Based on cell shape:

• Cocci are small, spherical cells. They group together in pairs (diplococci), in irregular groups or clusters (staphylococci), in rows (streptococci), and in packets (sarcinae).
• Bacilli are short, cylindrical, rod-shaped cells. They may occur as pairs or chains.
• Vibrio are comma-shaped cells.
• Spirilla are rigid, spiral-shaped cells. Spirochetes are long, thin, spiral-shaped cells, which are more flexible