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

Carbohydrates: Primary Energy Source

Carbohydrates are chemical compounds of oxygen, carbon, and hydrogen, synthesized by plants through the action of solar energy. Sugars are found in bread, grains, fruits, and vegetables.

They serve as the first major energy substrate, providing between 50% and 60% of the total energy necessary for movement and basic functions. They are also essential to feed the brain.

Fats (Lipids)

Fats (lipids) consist of hydrogen, oxygen, and carbon that form a chain, categorized as saturated or unsaturated fatty acids.

Sources of Fats

• Saturated Fats: Meat, eggs, and dairy.
• Unsaturated Fats: Olive oil or sunflower oil.

Fats are indispensable; they serve as an energy source, help regulate body temperature (Tª), and transport... Continue reading "Essential Nutrients: Macronutrients, Vitamins, and Diet" »

Understanding Health & Disease

Health initiatives are often geared toward reducing exposure to various factors that are carcinogens, such as alcohol, tobacco, and diet. Recent years have spawned a new area of scientific knowledge: epigenetics, which studies the influence of the environment on gene expression.

Mental Health Conditions

Some diseases of the nervous system are due to malfunctioning neurons or injuries provoked by varied causes, such as high blood pressure, strokes, or lack of blood supply. The most important mental health challenges include:

• Depression

  Characterized by deep sadness and an incapacity to lead a normal life.

• Schizophrenia

  A disease that can present from adolescence, provoking serious personality disorders and disconnecting

Biological Organization: From Subatomic to Organismal Levels

Matter is organized into different degrees of complexity, forming the hierarchical structure of life. These levels include:

• Subatomic Level: Particles that make up atoms (e.g., protons, neutrons, electrons).
• Atomic Level: Formed by individual atoms (e.g., carbon, oxygen, hydrogen).
• Molecular Level: Resulting from the linkage of different atoms. Molecules can be inorganic (e.g., water, salts) or organic (e.g., proteins, carbohydrates, lipids, nucleic acids), with organic molecules being fundamental to living material.
• Cellular Level: The first level of life; the smallest unit capable of independent existence.
• Tissue Level: A network of specialized cells with the same function and origin.

The Heart: Structure and Function

The heart is a contractile, muscular organ, roughly the size of a fist and conical in shape. Its primary function is to pump blood to reach all parts of the body. The heart is situated above the diaphragm, nestled between the lungs.

The heart is composed of two distinct halves, separated by a septum, which ensures the right and left halves do not communicate directly. Each half of the heart has two cavities:

• An upper, thinner-walled cavity called an atrium.
• A lower, muscular-walled cavity called a ventricle, which drives the blood.

Understanding the Cardiac Cycle

The period between the end of one contraction and the end of the subsequent one is called the cardiac cycle. It includes two main phases:

• Diastole: An expansion

The Fundamental Units of Life: Cells and DNA

The Cell: The cell is the basic unit of life. It can be divided into two distinct areas: the cytoplasm and the nucleus. The cytoplasm contains various cellular organelles, while the nucleus contains the genetic information that determines the characteristics of every individual: DNA.

Chromosomes and Genes

Chromosomes:

• Tiny threadlike structures found in the nucleus of eukaryotic cells.
• Contain nucleic acids, specifically DNA (deoxyribonucleic acid), and proteins.
• Divided into smaller units called genes.
• The number of chromosomes is characteristic of each species. For example, human cells have 46 chromosomes grouped in pairs, while reproductive cells (gametes) have 23.

Genes:

• The basic unit of heredity in

Common Foodborne Pathogens and Their Sources

• Clostridium botulinum: Causes botulism, often found in soil or dust.
• Vibrio cholerae: Causes cholera, transmitted by fecal matter.
• Salmonella enterica subsp. enteritidis: Causes salmonellosis.
• Salmonella enterica subsp. Typhi: Causes typhoid fever.
• Shigella: Causes shigellosis.
• Brucella melitensis: Causes brucellosis, transmitted by infected animals.
• Bacillus cereus: Found in soil and dust.
• Campylobacter jejuni: Transmitted by infected animals.
• Clostridium perfringens: Found in soil and dust.
• Escherichia coli: Associated with fecal contamination.
• Listeria monocytogenes: Transmitted by infected animals.
• Yersinia enterocolitica: Transmitted by infected animals.
• Vibrio parahaemolyticus: Transmitted by infected animals.

Understanding Cells: The Basic Units of Life

Fundamental Biological Units

• Cell: The structural and functional unit of all living beings. Cells originate from pre-existing cells.
• Abiotic (Non-Living Components): Subatomic particles, atoms, molecules, macromolecules, supramolecular complexes, and organelles.
• Biotic (Living Components): Cellular level, tissues, organs, organ systems, individuals, populations, communities, ecosystems, and the ecosphere.

Prokaryotic Cells: Simple Cellular Organization

Prokaryotic cells lack a true nucleus and other membrane-bound organelles.

• Cell Wall: A rigid and strong protective layer formed by polysaccharides and proteins.
• Plasma Membrane: Located inside the cell wall, it controls the entry and exit of substances.
• Bacterial

Interaction

Interaction is the set of processes through which a living being obtains information from the environment, takes decisions, controls its actions, and coordinates the functioning of the body itself.

Obtaining Information

There are various mechanisms responsible for obtaining information from the exterior and the interior of the body. These mechanisms are called receptors.

Analysis of the Information and Elaboration of a Response

This process is carried out by the nervous system and the endocrine system. The elaborated response is an order that is transmitted to the organs via different procedures.

Execution of a Response

The effectors, which are the organs responsible for carrying out a response, are as varied as the possible responses... Continue reading "Interaction: Obtaining, Analyzing, and Executing Responses in Living Beings" »

Taxonomy and Systematics: Classification Principles

Taxonomy is a scientific discipline concerned with the classification of living things, based on a hierarchical system of groups sorted according to their similarities.

The Linnaean System of Classification

The current system is based on that proposed in 1735 by Carolus Linnaeus. Living things are grouped into taxonomic categories:

• Species are included in genera.
• Several genera comprise the family.
• Families are grouped into orders.
• Orders are grouped into classes.
• The next category is the phylum (for animals and protists) or division (for plants and fungi).
• The highest taxonomic level is the kingdom.

Taxonomy helps establish relationships within different groups according to shared morphological, physiological,... Continue reading "Biological Classification: Taxonomy, Phylogeny, and Anatomy" »

Evolutionary Concepts and Theories

Pre-Evolutionary Ideas

Before modern evolutionary theory, several ideas attempted to explain the diversity of life:

• Fixism: This theory posited that species remain unchanged since their divine creation.
• Catastrophism: Proposed that Earth's history was shaped by sudden, short-lived, violent events, leading to the extinction of species, after which new species would appear.

Key Evolutionary Theories

Lamarckism: Inheritance of Acquired Characteristics

Jean-Baptiste Lamarck proposed that living organisms change throughout history. His theory was based on the following principles:

• Tendency Towards Perfection: Living things strive for perfection.
• Adaptation to Environment: Organisms adapt to their environment, and environmental