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

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" »

VIRUS H5N1

1a) Genetic Changes and Protein Expression

Changes are mutations of genetic material. Proteins are bound to gene expression. Genetic mutations must occur, or changes in proteins result from the translation process.

b) Immunity to H5N1

No person has been documented as having been infected with H5N1 antigens and subsequently acquired immunological memory that protects them.

2. Vaccine Efficacy and Viral Mutation

A vaccine produces a primary immune response (antigen-antibody) and a vaccinated person acquires immunological memory to respond effectively to the infection. Therefore, injecting a non-replicating virus (which possesses the same antigen) is difficult. In the case of the H5N1 virus, if it mutates easily, the vaccine might no longer... Continue reading "Understanding Viral Mutations and Immune Responses" »

Changes achieved through the development, acquisition, or loss of organs are maintained and transmitted to offspring, which preserves and increases these traits through successive generations. This concept is known as the inheritance of acquired characteristics. However, analysis of these proposals has not demonstrated any inherent tendency or impulse towards complexity in living things. In light of developments in genetics, the inheritance of acquired characteristics is not supported.

Natural Selection: Darwin and Wallace

Darwinian theory posits that in a changing world, organisms also change over time. Some features disappear, and new ones emerge. This process of change is gradual and continuous. Organisms with similarities are related and... Continue reading "Evolutionary Theories: Darwinism, Neo-Darwinism, and Hominid Origins" »

Waste Products

Non-Nitrogenous Products

These include CO2, H2O, mineral salts, and bile pigments. CO2 is removed by respiration. H2O is eliminated through the excretory apparatus and perspiration. Minerals are excreted in urine and sweat, and bile pigments pass out through the digestive system in the feces.

Nitrogenous Products

These are highly toxic compounds eliminated in various forms, such as ammonia, uric acid, and urea. They are categorized into three groups based on the primary excretion product:

• Ammoniotelics: The excretion product is ammonia. Due to its high toxicity, only organisms with abundant water supply can excrete nitrogen this way.
• Uricotelics: The excretion product is uric acid, which is ejected in crystal form. Its toxicity is