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

The cell is the basic unit of which they are made all living things. It is the smallest unit capable of performing all the functions that characterize a living being.

Depending on whether a body is formed by one or more cells can be:

Unicellular organisms. They consist of a single cell that performs all the functions necessary for survival. Sometimes, several single-celled organisms living together colonies. (like amoeba)

Multicellular organisms. Consist of multiple cells that lose the ability to survive alone. Each cell performs a specific task, and all work together to survive the body (such as plants and animals). Our body is composed of a large number of cells. People are multicellular beings.

The cells in our body can have different shape... Continue reading "The cell, the respiratory system, the organelles, gases, diffusion, active transport ..." »

Spine Structure and Biomechanics

Primary Functions of the Spine

• Support and movement of the trunk.
• Protection of the spinal cord.
• Absorption of shock between the ground and the brain.

Vertebral Column Composition

The vertebral column consists of 33 vertebrae:

• 7 Cervical vertebrae
• 12 Thoracic vertebrae
• 5 Lumbar vertebrae
• 5 Fused Sacral vertebrae
• 4 Fused Coccygeal vertebrae

The Motion Segment

A motion segment consists of two adjacent vertebrae and the intervening soft tissue. Each segment contains three articulations:

• The Intervertebral Disc (a symphysis joint).
• The right and left Facet Joints (gliding synovial joints).

Intervertebral Discs

These are fibrocartilage structures connecting adjacent vertebrae, accounting for 20–25% of the spine's total height.

Annulus

Chemistry Fundamentals and Reactions

Chemical Bonding Types

• Ionic Bonding: Metal + Non-metal → Electrons are transferred.
• Covalent Bonding: Non-metal + Non-metal → Electrons are shared.

Chemical Naming Conventions

• Ionic Naming: Metal + Non-metal (ending in “-ide”). Use Roman numerals for multivalent metals. Includes polyatomic ions.
• Molecular Compounds: Use prefixes (mono-, di-, tri-, etc.).
• Diatomic Elements: H₂, O₂, F₂, Br₂, I₂, N₂, Cl₂.

Properties of Compounds

• Ionic Compounds: Solid state, high melting/boiling points, conducts electricity when dissolved (aqueous).
• Molecular Compounds: Low melting/boiling points, poor electrical conductors.

Balancing Chemical Equations

The process follows the Law of Conservation of Mass:

1. Word Equation
2. Skeleton

Nervous System Anatomy

• Functions:

  • Controls perception (sight, touch, hearing, taste).
  • Maintains homeostasis (e.g., blood pressure, body temperature).

• Divisions:

  • Central Nervous System (CNS): Brain & spinal cord (processes information and sends responses).
  • Peripheral Nervous System (PNS): Motor & sensory neurons connecting the CNS to the rest of the body.

• PNS Subdivisions:

  • Somatic Nervous System: Controls voluntary movement (e.g., moving hands).
  • Autonomic Nervous System: Controls involuntary functions (e.g., heart rate).
    • Sympathetic Division (Fight or Flight): Increases alertness, heart rate, etc.
    • Parasympathetic Division (Rest & Digest): Slows heart rate, promotes digestion, etc.

• Structural Differences (Autonomic):

  • Parasympathetic: Long preganglionic

Kingdom Monera

• Prokaryotic organisms: Includes Archaebacteria and Eubacteria.
• Archaebacteria: Includes Methanogens (found in marshes), Thermoacidophiles (heat-resistant), and Halophiles (salt-tolerant).
• Eubacteria: True bacteria.

Kingdom Protista

• Single-celled eukaryotes: Diverse group of microscopic organisms.
• Chrysophytes: Includes diatoms with soapbox-like shells; their gritty soil is used in oil filters.
• Dinoflagellates: Possess two flagella and cellulose plates.
• Euglenoids: Have a pellicle; can be both autotrophic and heterotrophic.
• Slime Moulds: Saprophytic organisms that form aggregates called Plasmodium (e.g., Physarum).
• Protozoans: Includes amoeboid, flagellated, ciliated, and sporozoan types.

Kingdom Fungi

• Examples: Wheat rust (Puccinia) and

Number and Quantity Prefixes

• Mono-, Uni- (one):
  • Monodiplopia: Double vision that occurs only in one eye.
  • Unilateral: Confined to one side only.
• Bi-, Di- (two, twice, double):
  • Diplopia: Double vision.
  • Bilateral: Affecting two sides.
• Tri- (three):
  • Trigeminal nerve: The fifth cranial nerve, providing sensory innervation to the face, divided into three main branches.
• Quad-, Quadra-, Tetra- (four):
  • Quadrant: Areas divided for descriptive purposes into quadrants.
  • Tetradactyl: Having four fingers or toes on a hand or foot.
• Multi- (many):
  • Multicellular: Composed of many cells.
• Poly- (too much, many):
  • Polyuria: Excessive excretion of urine.
• Hemi-, Semi- (half or partly):
  • Hemiplegia: Paralysis of one side of the body.
  • Semicomatose: State of drowsiness and inaction, requiring

Porifera and Cnidarians: Structure

Porifera (sponges) and Cnidarians (anemones, corals, and jellyfish) are simple, aquatic invertebrates.

Porifera (Sponges)

• Mostly marine, some freshwater species
• Bag-shaped body with pores that communicate with the atrial cavity
• The atrial cavity connects with the exterior through the osculum
• High capacity for regeneration

Cnidarians

• Anemones, corals, and jellyfish (all marine), hydra (freshwater)
• Radial symmetry
• Soft body with a single opening surrounded by tentacles
• Stinging cells (cnidocytes)
• Gastrovascular cavity that functions as a stomach
• Carnivorous
• Two forms:
  • Polyps: Tubular, bag-shaped with the opening at the top
  • Medusae: Umbrella-shaped, actively swim or float in the water

Worms: Platyhelminthes, Nematodes, and Annelids

Worms... Continue reading "Invertebrate Animals: Characteristics and Classification" »

The Nitrogen Cycle: Essential Biogeochemical Process

Question: Briefly explain the nitrogen cycle with a diagram.

Answer: The nitrogen cycle is a biogeochemical process where nitrogen is converted between different chemical forms as it moves through living and non-living components. It plays a crucial role in maintaining the nitrogen balance in ecosystems.

Stages of the Nitrogen Cycle

The nitrogen cycle consists of several important steps:

1. Nitrogen Fixation
2. Nitrification
3. Assimilation
4. Ammonification (Decay)
5. Denitrification

1. Nitrogen Fixation

Atmospheric nitrogen ($ ext{N}_2$) is inert, meaning plants and animals cannot directly use it.

• Certain bacteria, such as Rhizobium & Azotobacter, known as nitrogen-fixing bacteria, convert $ ext{N}_2$ gas into