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

Key Definitions in Health and Disease

Agent: An animate or inanimate entity whose presence or absence can disrupt host health.

Host: Any organism capable of harboring an agent.

Environment: The complex of factors influencing a system, determining its course and way of life.

Stimulus Trigger: A factor or condition arising after a disturbance in the ecological triad's balance, initiating the disease process.

Sign: A measurable or quantifiable manifestation in an individual.

Symptom: A subjective expression of a condition reported by an individual.

Latency: A stable phase in disease evolution without subclinical manifestations, signs, or symptoms.

Causality: Conditions involving agent, host, environment, and transmissibility factors that generate a stimulus... Continue reading "Understanding Health: Agents, Hosts, and Environmental Factors" »

Invertebrate Excretory Systems (Protonephridia): These are found in animals with no coelom, such as flatworms. They consist of highly branched tubes that end in a few cells with cilia (flame cells) or flagella (solenocytes). Both cilia and flagella are located in the lumen of the tube, and their movement causes the continuous elimination of waste substances. (Metanephridia): This system occurs in coelomates (annelids, mollusks, etc.). It is made up of a coiled tube surrounded by a capillary network, with two openings: the external (nephridiopore) and internal (nephrostome), which opens into the coelomic cavity. Inside the metanephridia, reabsorption occurs for compounds that are still useful, while waste substances are expelled outside through... Continue reading "Understanding Invertebrate and Vertebrate Excretory Systems" »

Unit 10: The Basis of Heredity - Molecular Genetics

Basics of Genetics

• Gene: Each piece of DNA containing information for one character.
• Alleles: Each form a gene can have.
• Locus: The physical location a gene occupies on a chromosome.
• Loci: The place occupied by several genes.
• Diploid Organisms: Individuals who have two alleles for each gene, one from the mother and one from the father. This is represented as 2n.
• Haploid Organisms: Individuals that have only one gene for each character. This is represented by n.
• Gamete: A sexual reproductive cell, haploid (n), produced by meiosis.
• Genotype: The set of alleles of an individual for one or more characters.
• Phenotype: Each of the aspects or observable manifestations of a character.
• Phenotype = Genotype +

Lipids

Functions of Lipids

• Energy Storage: Lipids serve as the primary energy reserve in the body.
• Structural Components: Lipid bilayers form the plasma membrane and other cell organelles.
• Protection: Lipids cushion vital organs, like the kidneys, and protect body surfaces (e.g., waxes on hair and fruit).
• Biocatalysis: While not all lipids are biocatalysts themselves, some play a role in biocatalyst synthesis.
• Transport: Lipids are emulsified and transported from the intestine to either storage in adipose tissue or sites of utilization.

Amino Acids

Amino acids are small organic compounds characterized by a carboxyl group and an amino group. They are solid, crystalline, water-soluble, have high melting points, and exhibit optical activity. Primary amino... Continue reading "Lipids, Amino Acids, and Proteins: Structure, Function, and Properties" »

1. Health and Disease

When all organs and body systems function correctly, we consider ourselves healthy. If any part of the body is impaired and cannot perform its function properly, it causes disease. When a person becomes ill, characteristic symptoms of the disease appear, often accompanied by some deterioration. Key factors in maintaining health include:

• A proactive approach to health.
• Adopting healthy habits and lifestyles.
• Personal characteristics such as age or hereditary factors.
• An effective health system.

2. Disease Categories

Diseases can be categorized in various ways:

• Infectious: Caused by microorganisms that enter the body and can be transmitted from person to person.
• Non-infectious: Not caused by microorganisms and therefore not transmitted

Understanding Ecosystems and Their Dynamics

What is an Ecosystem?

An ecosystem is a natural system consisting of all living beings inhabiting a place (the biocenosis) and the physical and chemical characteristics of that site (the biotope). A multitude of relationships are established between the biotope and biocenosis.

Trophic Relationships

Trophic relationships are those established in an ecosystem through feeding, illustrating how energy and nutrients flow.

Key Components of an Ecosystem

Producers

Producers are autotrophic living beings. They produce their own food from inorganic material and an energy source (like sunlight), forming the fundamental base of all ecosystems.

Consumers

Consumers are heterotrophic organisms that obtain energy by feeding... Continue reading "Ecosystems Explained: Components, Interactions, and Cycles" »

Airway

Includes a conduction pipeline connecting it with the exterior lungs, which are:

• The nasal cavities: Two open cavities covered by nasal mucous. They communicate with the exterior through the nostrils and with the pharynx through the choanae (posterior openings).
• The pharynx: It is a common respiratory tract through the digestive tube and the epiglottis. The epiglottis is located above the larynx and prevents food from entering during swallowing, thus avoiding choking.
• Larynx: Communicates with the trachea and contains some folds (vocal cords) that vibrate and emit sounds.
• The bronchial tree: It consists of two bronchi that penetrate the lungs and branch into increasingly smaller bronchioles. The cells of the walls secrete mucus and have cilia,

Fixism (Cuvier) or fijista theory is a belief that holds that existing species have remained essentially unchanged since they were created, therefore, immutable. The fossil remains of animals would be killed in the biblical flood or by the vagaries of nature (as theories such as vis plastica).
Now become (Lamarck 1809): Progression from simple organisms to complex plants and animals, ultimately reaching humans. "Existence impulse towards perfection" - Cap. of the organisms for adaptability to environmental changes - Principle of use and disuse of organs - Inheritance of acquired characteristics.
Compression Fossils and Printing: This occurs when an organism is caught or parts of it are covered by sediments without decomposing, resulting in... Continue reading "Understanding Fixism and Evolutionary Concepts" »

Tracheophytes: The Vascular Plants

Key Features of Tracheophytes

• Also known as vascular plants due to their specialized conducting vessels (xylem and phloem).
• Possess true roots, stems, and leaves.
• Exhibit autotrophic nutrition, producing their own food through photosynthesis.
• Develop three primary tissue systems: vascular, ground, and dermal tissues.
• Many species reproduce via seeds, though some reproduce by spores.

Classification of Tracheophytes

• Lycopsida
• Sphenopsida
• Psilopsida

Ferns: Non-Seed Vascular Plants

Characteristics of Ferns

• Comprise approximately 10,000 known species.
• Typically herbaceous and rhizomatous (possessing underground stems).
• Often thrive in warm, humid environments, particularly in tropical forests.
• Possess true roots, stems, and leaves

Chromatin

Chromatin consists of strands of DNA at different degrees of condensation associated with proteins and scattered throughout the nucleoplasm. When the cell is going to divide, the chromatin filaments are organized and condensed to form thicker structures called chromosomes.

Genes

A gene is a unit of hereditary material. It is a fragment of nucleic acid that carries genetic information for a character, a protein, or a polypeptide chain. It corresponds to what Mendel called a hereditary factor.

Centriole

In animal cells, centrosomes present two small cylinders and consist of protein tubules.

Mitotic Spindle

The mitotic spindle forms when the nuclear membrane and nucleolus disappear.

Karyotype

A karyotype is a set of chromosomes from one species.... Continue reading "Cell Biology: Chromatin, Genes, Karyotype, and Cell Types" »