Notes, abstracts, papers, exams and problems of Biology

Eradication of Diseases Worldwide

If we tried to reach all the world, including countries that are not even developed, we could eradicate diseases.

The Relationship Between Diseases and Microorganisms

Pasteur established for the first time the relationship between certain diseases and the presence of microorganisms in the patient, but the mere observation of microorganisms with the disease does not guarantee that it will cause it.

Ebola Virus: A Highly Contagious Disease

The Ebola virus is the cause of Ebola viral hemorrhagic fever, an infectious, highly contagious, and very severe condition that affects both animals and humans. The virus is transmitted by direct contact with infected bodily fluids such as blood, saliva, sweat, urine, or vomit.... Continue reading "Understanding Common Infectious Diseases and the Immune System" »

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" »

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" »

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:

**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

What are Plant Hormones?

Plants require light, carbon dioxide, water, and minerals, including nitrogen, for growth. Utilizing energy from the sun, they produce much of their own substance, transforming simple materials into complex organic compounds. Hormones play a crucial role in regulating plant growth and development by stimulating or inhibiting specific processes. Among the most important internal factors are plant hormones. By definition, hormones are substances produced in one tissue and transported to another, where they exert highly specific effects.

Types of Plant Hormones

Among the many plant hormones identified, the best known are auxins, cytokinins, gibberellins, abscisic acid, and ethylene.

Auxins

Auxins are a group of plant hormones... Continue reading "Plant Hormones: Types, Functions, and Effects on Growth" »

Cellular Biology: Functions, Nutrition, and Systems

All living things are composed of cells. In multicellular organisms, cells consist of a plasma membrane, nucleus, cytoplasm, and organelles. Cells perform vital functions necessary for life: nutrition, relationships, and reproduction. In multicellular beings, cells are grouped into tissues, tissues into organs, organs into systems, and finally, all these form a complete living being.

Internal Environment and Homeostasis

The internal environment is regulated by homeostatic mechanisms, which are controlled by the brain. Nutrients from the digestive tract are broken down into simpler substances that are absorbed into the animal's internal environment. Aquatic animals obtain oxygen dissolved in water,... Continue reading "Cellular Biology: Functions, Nutrition, and Systems Explained" »

Cytoplasm

The cytoplasm is located just after the plasma membrane. Its components are mostly water, which acts as a solvent, and proteins that function as enzymes.

Chloroplasts

Chloroplasts produce nutrients from the sun's radiant energy through photosynthesis. They have two membranes: an outer and an inner smooth one. The inner membrane has folds called lamellae, which are located in the grana.

Mitochondria

Mitochondria oxidize food through cellular respiration and store the released energy. They are surrounded by two membranes: a smooth external surface and internal folds or ridges.

Endoplasmic Reticulum

The endoplasmic reticulum has a membrane structure that connects easily with the membrane of the nucleus and has compartments called cisterns.... Continue reading "Cellular Components and Transport Mechanisms" »