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

Sweat

Sweat glands are located in the skin, opening to the epidermis through pores. These glands are mainly concentrated in areas like the forehead, armpits, palms, and soles of the feet. Each gland consists of a thin tube called a glomerulus, which extracts fluid from blood capillaries. This fluid contains compounds like urea and water, similar to urine but more dilute. From the glomerulus, sweat travels through channels to the pores and is released as droplets.

Regulating Urine Concentration

Urine concentration depends on the permeability of the collecting tubules, regulated by the antidiuretic hormone vasopressin. Increased osmotic pressure stimulates vasopressin secretion, increasing the permeability of the collecting tubules. This leads... Continue reading "Understanding Sweat, Urine, and Osmoregulation" »

Protective Tissues

Epidermal Tissue

This outermost layer covers roots, herbaceous stems, and leaves. It consists of a single layer of living cells without chlorophyll, tightly arranged without spaces. The outer cell wall is covered with a cuticle, a waterproof layer made of cutin and waxes. In aerial parts, the epidermis protects stems and leaves, regulates perspiration, and facilitates gas exchange. In roots, it protects and aids water and salt absorption through root hairs. Trichomes, also present in the epidermis, provide additional protection.

Cork Tissue (Suber)

This tissue replaces the epidermal tissue in older plant parts. It comprises multiple layers of dead cells coated with suberin, making it highly waterproof. Due to cell activity, the... Continue reading "Plant Tissues and Their Functions" »

Relation Functions in Organisms

Relation functions are those that allow a living being to receive information from the outside or inside, and respond to it in the most appropriate way for their survival.

Components of Relation Functions

Organisms must have the means to receive the stimuli (receptors), systems for processing data (coordination systems), and mechanisms to implement the response (effectors).

Stimuli

Stimuli are changes that occur in the external environment, but also those taking place within their own organism.

External Stimuli

These are changes occurring in the environment that receptors detect. Examples: wind, rain, etc.

Internal Stimuli

These are variations that occur within the body. Examples: temperature self-regulation, urination,... Continue reading "Relation Functions in Living Beings" »

The Double Helix of DNA

Deoxyribonucleic acid (DNA) is a molecule composed of simpler molecules: a pentose sugar called deoxyribose, phosphoric acid, and four nitrogenous bases: adenine (A), thymine (T), guanine (G), and cytosine (C).

DNA is formed by two antiparallel strands of DNA. This double chain is held together by hydrogen bonds that are established between their nucleobases. This forms the characteristic double helix structure of DNA.

Its function is to carry the genetic information encoded in a living organism and it has the ability to replicate itself.

DNA Replication

The information contained in DNA encodes all the bases, the basic pattern of inheritance of each species. It contains all the information that needs to be transmitted intact... Continue reading "DNA and RNA: Structure, Replication, and Mendel's Laws" »

The Fundamental Characteristics of Bacteria

Bacteria are prokaryotes. The absence of compartments separated by membranes means metabolites are disseminated throughout the cytoplasm. Despite this structural simplicity, bacteria are complex and diverse creatures from a biochemical viewpoint, which has enabled them to adapt to varied conditions.

Size and Structure

Most bacterial cells are very small: their volume is about one thousandth the size of the smallest eukaryotic cells. They are typically about 1 micrometer ($\mu$m) in diameter and 0.2 to 3-4 $\mu$m long. Most bacteria are unicellular organisms, but some form colonies or filaments, sometimes exhibiting cell specialization.

Basic Bacterial Shapes

Although many species have irregular shapes,... Continue reading "The Essential Characteristics of Prokaryotic Bacteria" »

Fixism vs. Evolutionism

To understand our present and future, it is crucial to know our origins. One key concept in this understanding is evolution, the theory that the universe and life are products of development, change, and adaptation, leading to the diversity of species. This stands in contrast to Fixism.

Fixism is a conception of living beings encompassing various theories. In our culture, the most widespread is the one that follows the Genesis narrative of the Bible. Proposed by George Cuvier, this theory posits that all species are independent and remain unchanged over time.

Lamarckism

This theory, proposed by Lamarck, applies primarily to animals and represents the first comprehensive theory of biological evolution. Lamarck's theory is... Continue reading "Evolutionary Theories: From Fixism to Neo-Darwinism" »

Toxins

• Toxins:

• Main Routes of Transmission of Infectious Diseases and Examples

In any infectious disease, a pathogen must pass from a healthy host to another to become a new host. Transmission can occur through:

• Transmission by direct contact: injuries, sexually, via parental (mother to fetus). Examples:

Understanding Sensory Receptors

Receptors are specialized structures that convert environmental stimuli into nerve impulses. They are crucial for our interaction with the world, translating various forms of energy into signals our brain can interpret.

What are Receptors?

Receptors are categorized based on their location and the type of energy they react to:

• Location-based Classification:
  • Exteroceptors: Located on the body surface, they detect external stimuli (e.g., touch, temperature, light, sound).
  • Interoceptors: Located internally, they detect internal stimuli (e.g., blood pressure, body temperature, pain).
• Energy-based Classification:
  • Mechanoreceptors: Respond to mechanical stimuli like pressure, touch, vibration, and stretch.
  • Chemoreceptors: Detect

**We Manage the Disease**

*Pathology*

Pathology, the science of disease, is the basis of diagnosis.

• Etiology studies the causes of diseases.
• Pathogenesis investigates the mechanism of action of the disease.
• Pathological anatomy seeks to know the outcome of the disorder and injuries.
• Pathophysiology analyzes the functional changes that the patient undergoes.

Clinical Signs and Symptoms

The clinic studies the signals that reveal the disease. Signs include pulse, artery pressure, and temperature. Symptoms and investigations provide additional information, such as radiographs.

**Infectious and Parasitic Diseases**

Infectious and parasitic diseases are caused by biological pathogens.

• Incubation is the time from the entry of the pathogen into the body until

The Immune System: Body's Defense Mechanisms

The body's defense mechanisms protect us against various pathogens such as viruses, bacteria, fungi, protozoa, extraneous cellular tissue introduced from outside (e.g., in transplantation), and cells transformed into malignant or cancerous forms. The set of biological structures that enable specific defense against these agents constitutes the immune system, and all such defense mechanisms provide immunity. The science of studying the immune system is called immunology.

Types of Immunity: The Body's Defense Lines

The body has three lines of defense against microbial attacks:

• First Line: External Barriers

  These prevent microorganisms from entering the body.

• Second Line: Non-Specific Internal Defenses

  These