Levels of Organization in Living Beings

Levels of organization refer to the different degrees of complexity in organized matter.

• Subatomic level: Particles that make up atoms (protons, neutrons, electrons).
• Atomic level: Formed by atoms; the smallest constituents of matter that retain their properties.
• Molecular level: Molecules resulting from the binding of different atoms. There are two types:
  • Inorganic: Found in non-living or dead material (water and mineral salts).
  • Organic: Found only in living matter, usually polymers, chains formed by the union of a similar type of monomer molecules.
• Cellular level: The first level with life.
• Tissue level: Groups of cells with the same function and similar structure.
• Organ level: Different tissues are grouped for a particular function.
• System level: Sets of organs that perform a similar function and are formed by the same types of tissues.
• Apparatus level: Different sets of organs with specific functions that are involved in higher functions.
• Organism level: All living beings as a whole. Organisms can be:
  • Multicellular: Composed of many cells.
  • Unicellular: Consist of a single cell.

Cellular Structures and Organelles

Key components within a cell and their functions:

• Membrane: A thin layer surrounding the cell that protects it and controls the entry of nutrients and the outflow of waste substances.
• Cytoplasm: The aqueous solution inside the plasma membrane.
• Ribosomes: Responsible for the synthesis of proteins.
• Mitochondria: Responsible for cellular respiration.
• Endoplasmic reticulum: Storage and transport of proteins and lipids.
• Golgi complex: Ejects various substances.
• Vacuoles: Storage function.
• Lysosomes: Contain substances with digestive function.
• Centrosome: Controls cell movements and its participation in cell division.

Cell Nucleus

• Nuclear membrane: Surrounds the nucleus and is full of pores.
• Nucleoplasm: The aqueous solution inside the nucleus.
• Chromatin: Sets of long fibers (DNA) associated with cells that control cellular functions.
• Chromosomes: Formed when chromatin condenses.
• Nucleolus: Formed by RNA and proteins; responsible for the formation of ribosomes.

Tissue

Groups of similar cell types, that have a similar structure and perform the same functions.

Epithelial tissue: Cells that are close together, forming geometric layers. There are two groups:

• Epithelial linings