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

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" »

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

Types of Illness

• Physical Diseases: Caused by injury, infection, or degenerative processes in the body. They are classified into infectious and non-infectious diseases.
• Mental Illness: Provoked by a malfunction of the brain.
• Social Ills: Caused by the existence of a social environment with serious violent, economic, or educational deprivation.

Health vs. Illness

• Health: A state of complete physical, mental, and social well-being.
• Illness: The state in which a person's health is disturbed.

Violence as a Social Disease

Violence is a terrible social disease that kills many people every year. It is a disease that is incubated in childhood.

Viruses

Viruses are not living creatures but protein capsules containing DNA or RNA that is injected into a cell.

Infectious

Understanding Stem Cells and Pandemic Phases

Post-Pandemic Period Assessment

Following the pandemic, flu cases have become comparable to the usual seasonal flu patterns.

Stem Cells: Definition, Function, and Application

What Are Stem Cells?

Stem cells are progenitor cells that are self-renewing.

How Do Stem Cells Work?

Within the bone marrow, stem cells are found that reproduce identical cells through mitosis.

Where Are Stem Cells Located?

1. Cells in the blastocyst embryo state.
2. Organ-specific cells (e.g., bone marrow).

Stem Cell Capabilities

They are able to generate any cell type of the body.

Therapeutic Effect of Stem Cells

They function as restorative medicine for damaged tissues.

When Are Stem Cells Applied?

They are used in treatments, often alongside... Continue reading "Stem Cell Science and Global Pandemic Alert Levels" »

Biological Organization and Cellular Structure

Levels of Biological Organization

These levels grade the complexity of organization based on specific goals.

• Subatomic Level

  Particles corresponding to the atoms that make up protons, neutrons, and electrons.

• Atomic Level

  Composed of atoms, which are the smallest constituents of matter.

• Molecular Level

  Molecules that result from the binding of different atoms.

Chemical Components of Life

• Inorganic Molecules: Found in both living matter and inert substances (e.g., water and mineral salts).
• Organic Molecules: Exclusively found in living matter (e.g., carbohydrates, lipids, proteins).

Structural Levels of Life

• Cellular Level

  The first biotic level that is alive. Examples include epithelial, muscle, and osseous

DNA Replication: Semiconservative Process

DNA replication is a semiconservative process. It begins at replication origins, forming "bubbles."

Key Enzymes and Proteins in DNA Replication

• Helicases: Unwind the DNA double helix, moving in opposite directions from the origin.
• Topoisomerases: Act ahead of the replication fork to relieve supercoiling that arises from unwinding.
• SSB Proteins (Single-Strand Binding Proteins): Bind to and stabilize the separated single DNA strands, preventing them from re-annealing.

DNA synthesis always proceeds in the 5' to 3' direction, leading to two distinct modes of synthesis:

Continuous Synthesis (Leading Strand)

On the leading strand, synthesis is continuous. An RNA primase (a type of RNA polymerase) synthesizes a short... Continue reading "DNA Replication and RNA Transcription Processes" »

Sutton's Chromosome Theory of Inheritance

• Chromosomes occur in pairs.
• Chromosome pairs separate during meiosis.
• Each gamete carries one chromosome from each pair.
• Pairs of chromosomes separate independently of other pairs.
• Fertilization restores the paired condition of chromosomes in the zygote.

Mendel's Laws of Inheritance

• Factors (genes) occur in pairs.
• Factors segregate to form gametes.
• Each gamete carries a single factor.
• Pairs of factors separate independently of other pairs.
• Fertilization restores the paired condition of factors in the zygote.

Chromosomal Abnormalities

Trisomies

• Down Syndrome (Trisomy 21): Congenital mental disability, distinct facial profile, increased risk of illness, and heart defects.
• Patau Syndrome (Trisomy 13): Nerve abnormalities,

Historical Perspectives on Species Development

Humanity has conceived diverse theories throughout history to explain the origin and development of species. Two primary schools of thought emerged: Fixism and Evolution.

Understanding Fixism

Fixism is a theory asserting that living species have remained unchanged since their creation. It posits that species are immutable and have not derived from one another. This view often includes the idea that each species has a predetermined purpose within a hierarchical natural order.

Types of Fixism

• Early Philosophical Fixism

  Some early philosophical views, particularly from ancient Greece, suggested that species originated from fundamental elements (like the four elements) but then remained fixed in their form.