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

Infectious Diseases

Definition

Temporary or permanent loss of health caused by microorganisms.

Types of Microorganisms

• Bacteria: Unicellular prokaryotic organisms that multiply and can destroy cells and tissues.
• Viruses: Not considered living organisms. They reproduce by entering cells and using their resources, causing damage.
• Protozoa: Single-celled eukaryotes. Some cause disease.
• Fungi: Unicellular and multicellular eukaryotes. Some can cause disease in weakened individuals.
• Parasites: Multicellular organisms that live at the expense of a host, weakening but not killing it.
• Prions: Misfolded proteins that accumulate and cause neuron degeneration.

Non-Infectious Diseases

Nonspecific Defenses

Mechanisms that prevent the entry of microorganisms:

• Skin: Acts

Definition of Infectious Diseases

An infectious disease occurs when a parasite develops and multiplies within a host. The causal agent of transmissible diseases is usually a living organism that moves from one individual to another by contagion. The set of elements that define a communicable disease consists of:

• Reservoir: Where infectious agents are usually found.
• Source of Infection: Animate or inanimate object from which the causative agent originates.
• Mechanism of Transmission: The pathways that allow the causal agent of a transmissible disease to contact the host.
• Host: A person susceptible to contracting a communicable disease upon contact with the source of infection.

Samples arriving at the laboratory for the diagnosis of causative agents... Continue reading "Infectious Diseases: Definition, Transmission, and Diagnosis" »

Genetics and Heredity

Genetics is the science that studies how traits are inherited. Besides hereditary traits, external factors, including the environment, cause changes. Species variation is the manifestation of differences between individuals of the same species. The main causes are genetic variations.

Continuous and Discontinuous Variation

Continuous variation occurs when a trait has slightly different manifestations, like hair or skin color. Discontinuous variation occurs when a trait is clearly expressed as different and is genetically determined, not changing during an individual's life.

Phenotypic and Genotypic Variations

Phenotypic variations are observable traits (weight, height, color) resulting from the environment and genotype. Genotypic

Main Characteristics of Mammals

In general, mammals are characterized by the following:

• They are warm-blooded; their body temperature is constant.
• Mothers have mammary glands that produce milk for their young.
• The mouth is surrounded by lips, allowing young to suckle.
• They have abundant glands (sebaceous, sweat, and odoriferous) and are generally covered in fur, which they shed periodically.
• They have teeth to chew food.
• They have pulmonary respiration.
• Circulation is double (pulmonary and general).
• Most are viviparous: The embryo develops inside the mother and is nourished through the placenta.

Mammals are among the most highly evolved animals. They can live on land, fly, or live in the water.

Here, we will examine in more detail some common characteristics... Continue reading "Key Characteristics and Evolution of Mammals" »

Body Types can be graded on three components:

• Endomorphy: Refers to the predominance of curves and visceral development.
• Mesomorphy: Refers to the predominance of muscle and bone. Subjects are relatively strong.
• Ectomorphy: Highlights the prevalence of poor muscle development, resulting in greater fragility. Subjects typically have long and thin limbs.

In relation to the question of heritage concerning body type, there seems to be a consensus to accept its inherited character, manifesting at an early age.

The Growth of Different Body Systems

Nervous System

The nervous system shows growth and maturity very quickly. It is likely that after 7 months of age, nerve cell formation has not yet completed; however, there seems to be a predetermined sequence... Continue reading "Understanding Body Types and Their Developmental Growth" »

Carl Linnaeus: The Father of Modern Taxonomy

Although a practicing physician, Carl von Linnaeus had a deep interest in botany. He developed a revolutionary system to classify plants using a binomial method of scientific nomenclature. This simplified classification system organized plants and animals into meaningful groups based on their physical similarities.

Linnaeus also described and classified numerous animal species. His descriptions and classifications were so accurate that many of them have remained unchanged to this day.

Systema Naturae: Linnaeus's Most Important Work

Linnaeus's most important work is his Systema Naturae (1735), which saw numerous later editions. In each subsequent edition, he improved and completed his system. From the... Continue reading "Linnaeus's Binomial System: Foundations of Modern Taxonomy" »

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... Continue reading "Ecosystem Dynamics: Succession, Populations, and Growth" »

Blood Tissue

Blood is a tissue fluid that flows through the veins and arteries of all vertebrates. Its characteristic red color is due to the presence of the pigment hemoglobin in red blood cells.

Blood has a solid phase and a liquid phase, represented by the plasma. Its main function is the logistics of distribution and systematic integration.

Blood consists of formed elements and blood plasma.

Platelets

Platelets are small cell fragments (2-3 um in diameter), oval and without nuclei. They are produced in the bone marrow from the fragmentation of the cytoplasm of megakaryocytes. Their normal quantitative value is between 150,000 and 450,000 platelets per mm3.

They serve to plug injuries that could affect blood vessels. Platelets contribute to clot... Continue reading "Understanding Blood, Cartilage, Muscle, and Nervous Tissue" »

The Golgi Apparatus: Structure and Function

The Golgi Apparatus (GA) is found in all eukaryotic cells, essential in the transfer and packaging of products from the Endoplasmic Reticulum (ER), and involved in the synthesis of glycoproteins and mucopolysaccharides.

Distribution and Morphology

Its distribution depends on microtubules and motor proteins in secreting cells. In protein-secreting cells, the GA is located between the nucleus and the apical pole. In ganglion nerve cells, it is located around the nucleus with expansions to the cell surface. In Leydig cells, it is an ovoid mass located at one pole of the nucleus. In hepatocytes, it is distributed throughout the cytoplasm.

Its form differs from one cell to another and also within the same... Continue reading "Golgi Apparatus: Structure, Function, and Cellular Roles" »

Sensory Receptors

Sensory receptors are structures formed by nerve cells specialized to capture and transform stimuli into nerve impulses. The receptors are classified as:

• Chemoreceptors: Sensitive to chemicals.
• Mechanoreceptors: Sensitive to mechanical stimuli such as touch, pressure, sound, or gravity.
• Photoreceptors: Sensitive to light.
• Thermoreceptors: Sensitive to changes in temperature.
• Nociceptors: Sensitive to heavy pressure and responsible for pain.

Receptors can also be classified according to their location:

• Internal receptors: Located inside the body, particularly in the viscera. Responsible for collecting information from internal organs.
• External receptors: Located on the surface of the body. Responsible for collecting external stimuli