Characteristics of Living Things

Characteristics of Living Things

• Living organisms exhibit eight fundamental characteristics:
  • Cellular organization: Life's basic unit is the cell. Organisms are categorized as unicellular (one cell, e.g., bacteria) or multicellular (many cells, e.g., humans).
  • Movement: All organisms exhibit some form of movement, though the type and visibility differ. Animals move noticeably, while plant growth is a slower, less observable kind of movement.
  • Growth and Development: Organisms increase in size (multicellular by cell division, unicellular by cell enlargement).
  • Response to Stimuli: Living things react to changes in their environment (light, heat, chemicals, etc.) using specialized receptors.
  • Homeostasis: Maintaining a stable internal environment despite external changes (e.g., body temperature).
  • Reproduction: Creating new organisms of the same type, either sexually (two parents) or asexually (one parent).
  • Metabolism: Obtaining and using energy for processes like growth, development, and reproduction. Metabolism combines anabolism (building complex molecules) and catabolism (breaking down complex molecules for energy).
  • Adaptation: Adjusting to their environment to enhance survival.

Levels of Biological Organization

• Life exhibits increasing levels of complexity:
  • Cell: The smallest functional unit of life.
  • Tissue: Similar cells working together.
  • Organ: Tissues working together.
  • Organ System: Organs working together.
  • Organism: Organ systems functioning together.
  • Population: The same species living in a defined area.
  • Community: Different populations interacting.
  • Ecosystem: Organisms and their environment interacting.
  • Biosphere: All ecosystems on Earth.