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

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.

Fundamental Scientific Concepts

Biological Foundations

Cells and Life Functions

Cells are the basic structural, functional, and biological units of all known organisms. They are composed of organic and inorganic compounds.

The vital functions of living beings include:

• Nutrition: The process of obtaining and processing nutrients.
• Reproduction: The biological process by which new individual organisms are produced from their parents, ensuring the survival of the species.
• Relation: How living beings communicate and interact with their environment and each other, often involving the nervous system.

Organism Classification

The five biological kingdoms are:

• Monera
• Protoctists
• Fungi
• Plants
• Animals

Animal classification is used to sort and identify characteristics.... Continue reading "Fundamental Concepts in Science" »

Spermatophyte Cycle: Seed Plant Reproduction

Seed plants (Spermatophytes) are highly evolved organisms. Their life cycle involves distinct stages of reproduction.

The Sporophyte Stage and Male Structures

The Sporophyte is the entire plant, consisting of roots, stems, leaves, and flowers. In Angiosperms (flowering plants), the male reproductive part is the androecium, which is composed of stamens.

Anatomy of the Stamen

• A stamen consists of the anther and the filament.
• The anther contains two cavities called thecae.
• These thecae house the sacs that represent the microsporangia.

Male Gamete Formation (Pollen)

Inside the microsporangia, microspore mother cells form, which develop into pollen grains. When the microspore germinates, it originates the pollen

Understanding Heart Failure

Heart Failure (HF) is the inability of the heart to maintain adequate cardiac output to meet the patient's physiological needs.

Factors Influencing Cardiac Output

The primary factors influencing cardiac output are:

1. Distensibility: This is influenced by preload. An excessive increase in preload may be caused by conditions such as anemia, hyperthyroidism, or atrioventricular fistula.
2. Contractility: Often affected by conditions like myocardial infarction.
3. Afterload: Determined by the pressure in the aortic root.

Heart Failure Syndrome

The syndrome of heart failure is characterized by:

• Decreased Cardiac Output: Leading to lower blood pressure.
• Increased Secretion of Catecholamines: Which causes vasoconstriction, piloerection,

The Digestive System

Humans need to consume a range of foods from which they obtain the necessary materials and energy for their bodily functions. The body requires proteins, lipids, carbohydrates, vitamins, and minerals.

Understanding Nutrition

Nutrition is the biological function through which living organisms acquire and transform matter and energy from their environment. We can distinguish three main phases in nutrition:

• Ingestion
• Digestion
• Absorption

The digestive system is responsible for transforming food. This process occurs through various parts of the body:

• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Large Intestine
• Anus

Common Dental Diseases

• Gingivitis
• Periodontitis (Pyorrhea)
• Plaque
• Cavities

Diseases of the Digestive System

• Constipation and Diarrhea
• Peptic

Key Definitions in Health and Disease

Agent: An animate or inanimate entity whose presence or absence can disrupt host health.

Host: Any organism capable of harboring an agent.

Environment: The complex of factors influencing a system, determining its course and way of life.

Stimulus Trigger: A factor or condition arising after a disturbance in the ecological triad's balance, initiating the disease process.

Sign: A measurable or quantifiable manifestation in an individual.

Symptom: A subjective expression of a condition reported by an individual.

Latency: A stable phase in disease evolution without subclinical manifestations, signs, or symptoms.

Causality: Conditions involving agent, host, environment, and transmissibility factors that generate a stimulus... Continue reading "Understanding Health: Agents, Hosts, and Environmental Factors" »

The Human Ear: Structure and Function

The ear can be divided into three main sections: the outer ear, middle ear, and inner ear.

Outer Ear

• Auricle (Pinna)

  Consists of cartilage covered with skin. Its primary function is to collect sound waves and direct them into the ear canal.

• Ear Canal

  Extends from the auricle to the eardrum. It contains hairs to help keep out foreign bodies like insects and glands that secrete cerumen (earwax) to protect against water and debris.

Middle Ear

• Tympanic Membrane (Eardrum)

  A thin membrane that vibrates in response to sound waves.

• Ossicular Chain

  Consists of three tiny bones: the malleus (hammer), incus (anvil), and stapes (stirrup). These bones transmit and amplify vibrations from the eardrum to the inner ear.

Inner Ear

• Cochlea