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

Nutrition Defined

Nutrition is the set of processes by which living organisms transform energy and substances from their environment into their own organic molecules.

Types of Nutrition

• Autotrophs

  Organisms that are able to convert the sun's energy and mineral substances from water and soil into biomolecules.

• Heterotrophs

  Organisms in which nutrition occurs in living organisms that cannot capture the sun's energy, obtaining nutrients by consuming other organisms.

Nutritional Processes

1. Water ascends from roots to leaves through the xylem, which transports water, providing hydrogen.
2. Mineral salts dissolved from the soil provide essential elements like nitrogen, phosphorus, potassium, chloride, iron, magnesium, etc.
3. Carbon dioxide from the air provides

Ecosystem Dynamics: Matter and Energy Flow

Flow of matter and energy in the ecosystem: Environmental inorganic compounds and organic matter are processed in photosynthesis, then returned to the environment and can be reused by producers. Plants transform solar energy, which is stored and then ceded to the environment, where it cannot be used by living things.

Types of Pyramids

Energy: Each rectangle represents the energy stored. The rectangle representing producers is always larger. Each trophic level provides sufficient energy to support the level above it.

Biomass: These pyramids are constructed using data on the amount of biomass at each trophic level. These pyramids can sometimes be reversed.

Numbers: These rectangles represent the number of... Continue reading "Ecosystem Dynamics: Matter, Energy, and Population Changes" »

Plasma Membrane: Structure and Function

The plasma membrane is a semipermeable, fluid, flexible, and selective membranous structure that surrounds the entire cell. It consists of a phospholipid bilayer (semipermeable), proteins (transport and structural), carbohydrates (cell communication), and cholesterol (structural). Its functions are to:

• Protect the cell
• Contain the cytoplasm and its organelles
• Maintain cell shape
• Establish communication between the cell and its environment
• Limit the cell
• Manage transport within the cell

Types of Transport

Passive Transport

Passive transport is a type of transport that does not require energy expenditure. However, it does require certain conditions.

a) Diffusion

Diffusion is the transport of substances through a semipermeable... Continue reading "Plasma Membrane: Structure, Function, and Transport Mechanisms" »

The Stages of Evolution and Speciation

The evolution of changes in living things that occur over time, leading to new species, can be distinguished in four stages:

1. Production of Evolutionary Change

   Natural selection favors certain individuals while harming others. Both still belong to the same species.

2. Genetic Isolation of the New Population

   To constitute a new species, it's imperative that members of the new species do not reproduce with the originals. This occurs when the new settlement becomes genetically independent. Various types of barriers include:

   • Geographical Barriers

     Prevent physical contact between populations (among individuals).

   • Sexual Barriers

     Due to anatomical differences that prevent mating or lack of synchrony in the fertile period,

Plant Waste Products

Gaseous substances: These include carbon dioxide and ethylene. Carbon dioxide is removed via stomata and lenticels, while ethylene is found in ripe fruits.

Liquid substances:

• Essential oils are expelled to the outside (ciliary ganglion) or stored (oleifera bags).
• Resins accumulate in the resin canals.
• Latex is stored within laticiferous channels.

Solid substances: Calcium oxalate accumulates as crystals in cell vacuoles.

Plant Respiration

Plants, like most living organisms, require oxygen for cellular respiration. As photosynthetic organisms, they also require carbon dioxide to synthesize their own organic matter. The addition of these gases does not require a respiratory apparatus as in animals, due to the following peculiarities:... Continue reading "Plant Waste, Respiration, and Vertebrate Urine Formation" »

Antibody: Structure and Function

Molecules manufactured by B lymphocytes in response to contact with an antigen. Chemically, they are globular plasma proteins that detect and specifically bind to the antigen, leading to the humoral immune response. This allows them to detect and neutralize or bind to microorganisms that are then phagocytosed by macrophages.

Antigen: Immune System Trigger

A molecule capable of triggering an immune response. These molecules are foreign; the immune system does not recognize them as its own. They are detected by antibodies. Antigens are macromolecules of protein or polysaccharide nature.

Autoimmunity: Immune System Error

This occurs when the immune system synthesizes antibodies against the organism itself. It is an... Continue reading "Immune System Fundamentals: Key Concepts" »

The Anatomy of Human Phonation

The process of human voice production, known as phonation, involves a complex set of anatomical structures. These can be broadly divided into three distinct zones:

• Subglottic Cavity
• Larynx (Glottic Cavity)
• Supraglottic Cavity

Subglottic Cavity: The Powerhouse of Voice Production

The subglottic cavity comprises the diaphragm, lungs, bronchi, and trachea. This region is crucial for generating the airflow necessary for phonation.

The diaphragm is a muscular septum, shaped like a dome, that separates the chest and abdominal cavities. Its movement drives the respiratory cycle:

• Inspiration: When the diaphragm contracts and the ribs rise, the volume of the chest cavity increases. This draws outside air through the nose or mouth,

Proteins

Proteins are polymers of amino acids, also known as polypeptides. They are essential biomolecules, as nearly all life depends on them.

Protein Structural Levels

Proteins can have thousands of amino acids, and therefore, their thousands of atoms can adopt a wide variety of positions. Importantly, a protein consists of thousands of amino acids linked one after another through peptide bonds, forming long linear chains. However, the final spatial structure of a protein is not a linear chain; it adopts a specific three-dimensional form in space, which is essential for its function.

Primary Structure

Consists of the amino acid sequence of a protein. It is the most basic and arguably the most important level of structural organization.

Secondary

Sexual Reproduction in Plants

Understanding the Process

Sexual reproduction is typical of plants with seeds. The reproductive organs are inside the flower, where gametes are produced. After pollination, fertilization and the formation of embryos and seeds take place. Pollination is the transfer of pollen grains from the anther of the stamen to the stigma of the pistil.

Flower Structure

A flower is the reproductive unit of a plant. It consists of the following parts:

• Calyx: Green sepals which protect the developing flower.
• Corolla: Brightly colored petals.
• Stamen: The male reproductive organ of the flower. It consists of a stalk (filament) and sacs (anthers), where pollen is stored.
• Pistil: The female reproductive organ of the flower. It consists of

Lymphedema Clinical Presentation

• Increased limb volume:
  • Worsens during the day and is lower at night.
  • Decreases with elevation.
• Lower extremity involvement:
  • Often respects the sole of the foot.
  • Typically begins in the ankle.
  • Can progress to resemble an elephant's foot (elephantiasis), which is usually painless.

Temporal Clinical Classification of Ischemic Stroke

Transient Ischemic Attack (TIA)

• Episode of focal neurological deficit, short-term.
• Total recovery within 24 hours.
• No cerebral parenchymal necrosis.
• Current definitions often include standard imaging tests.

Reversible Ischemic Neurological Deficit (RIND)

• Neurological deficit lasting 24 hours and less than 4 weeks.

Established Stroke

• Focal neurological deficit remains unchanged since its onset.

Progressive