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

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

What is Agarose Gel Electrophoresis?

Agarose gel electrophoresis is a method used in biochemistry, molecular biology, genetics, and clinical chemistry to separate a mixed population of macromolecules, such as DNA, RNA, or proteins, in an agarose matrix.

Agarose is a natural linear polymer extracted from seaweed that forms a gel matrix via hydrogen bonding when heated in a buffer and allowed to cool. These gels are the most popular medium for separating moderate to large-sized nucleic acids due to their wide range of separation.

How Gel Electrophoresis Works

Gel electrophoresis separates DNA fragments by size in a solid support medium. The process involves:

• Sample Loading: DNA samples are pipetted into sample wells.
• Electrophoresis: An electric current

Nerve Histology

• Epineurium: Protects the entire nerve
• Perineurium
• Fascicle
• Axon: Conducts impulses
• Node of Ranvier: Speeds conduction

Spinal Cord Anatomy

Meninges and Spaces

• Epidural space
• Dura mater: Protects the spinal cord
• Subdural space
• Arachnoid mater: Protective membrane
• Subarachnoid space: Contains Cerebrospinal Fluid (CSF)
• Pia mater: Covers the spinal cord

Roots and Nerves

• Posterior root (dorsal root): Sensory input
• Spinal ganglion (dorsal root ganglion)
• Anterior root (ventral root): Motor output
• Spinal nerve: Mixed nerve
• Posterior ramus: Back muscles and skin
• Anterior ramus: Limbs and anterior trunk

Spinal Cord Structures

• Central canal: Contains CSF
• White matter: Conducting tracts
  • Posterior white column
  • Lateral white column
  • Anterior white column
• Gray matter
  • Posterior

DNA Replication: The Biological Mechanism

DNA replication is the essential process by which a cell creates an exact copy of its DNA prior to cell division (mitosis or meiosis). This critical event occurs during the S phase of the cell cycle.

Initiation: Unwinding the DNA

• Helicase: An enzyme that unwinds and separates the double helix by breaking the hydrogen bonds between nitrogenous bases, creating a "replication fork."
• Single-strand binding proteins (SSBs): Bind to single strands of DNA to keep them separated and prevent the helix from re-forming.
• Primase: Adds short RNA primers to the single-stranded DNA template. These primers are necessary for DNA polymerase to begin adding nucleotides.

Elongation and Synthesis

• DNA Polymerase III: Adds complementary

Perineum Anatomy

Perineum Structures

The perineum is a diamond-shaped space between the pubic symphysis (anteriorly), the coccyx (posteriorly), and the ischial tuberosities (laterally), lying just inferior to the pelvic diaphragm (levator ani and coccygeus).

It is divided transversely into two triangles:

• The anterior is the urogenital triangle, which includes the external genitals.
• The posterior is the anal triangle, which contains the anus.

The perineum is also divided into superficial and deep layers, with some muscles common to men and women.

Muscles of the Perineum and Pelvic Floor

Muscles making up the Urogenital and Anal (Pelvic) triangles/diaphragms include:

• Urogenital diaphragm: Superficial and intermediate planes
• Sphincters: Internal and external

Mitosis and Meiosis Comparison

Similarities Between Mitosis and Meiosis

• The sequence of changes in the nucleus and cytoplasm.
• The presence of the stages of prophase, metaphase, anaphase, and telophase.
• The spindle formation and the cycle of condensation of chromosomes.

Key Differences Between Mitosis and Meiosis

• Mitosis occurs in somatic cells, while meiosis is restricted to germ cells.
• In mitosis, each cycle of DNA replication is followed by one division. The resulting daughter cells are diploid (2n) and have the same amount of DNA as the parent cell.
• In meiosis, one DNA replication cycle is followed by two divisions, resulting in four haploid (n) daughter cells, which contain half the DNA of the parent cell.
• In mitosis, each chromosome behaves independently.

The Human Digestive System: An Introduction

The digestive system transfers organic nutrients, vitamins, minerals, and water from the foods we eat to the internal environment. Upon entering the body, food moves through the gastrointestinal (GI) tract, and the nutrients are absorbed and transported to the circulatory system where they are utilized.

Net Gain to the Body

Food and air are the primary sources of net gain to the body.

Distribution within the Body

Nutrients and substances are distributed throughout the body via the GI tract, lungs, storage deposits, and metabolism.

Net Loss from the Body

Excretion from the body occurs via the lungs, GI tract, kidneys, and skin.

Epithelial Cells

Epithelial cells separate compartments and are crucial in the digestive... Continue reading "Human Digestion and Metabolic Regulation" »

Pulmonary Ventilation and Gas Exchange

Pulmonary ventilation: This is the mechanism through which the air in the lungs and the respiratory tract is renewed. It allows air to flow in and out of the lungs. Ventilation is carried out through two respiratory movements: inhalation and exhalation. The diaphragm and the intercostal muscles mainly participate in these movements. By contracting and relaxing, these muscles produce changes in the volume of the lungs.

Inhalation

This is the movement that allows air to enter the lungs.

1. The diaphragm contracts, increasing the vertical diameter of the thoracic cavity.
2. The external intercostal muscles contract. The diameters of the thoracic cavity increase.
3. The lungs, which are elastic, expand.

Exhalation

This is... Continue reading "Human Physiology: Respiratory and Renal System Functions" »