Living Things Overview (pg. 16)

Living Things Overview

• Organisms are any living entities, varying in size from gigantic to microscopic.
• Exhibit different behaviors and have diverse food requirements.
• Share five key traits that define life.

Similar Traits of Living Things

• Organized structure with cells as the smallest unit of life.
• Can be unicellular (one-celled) or multicellular (many cells).
• Contain hereditary material, providing instructions for cellular function and organization.
• Respond to stimuli, with a stimulus causing a change and a response being the reaction to that change (e.g., hearing a fire alarm and leaving).
• Maintain homeostasis, ensuring stable internal conditions regardless of external changes.

Energy Utilization

• Living organisms require energy for organization and function.
• The sun is the primary energy source; organisms convert food into energy.
• Organisms take in oxygen, while green plants use carbon dioxide for photosynthesis.

Growth and Development

• Unicellular organisms grow by increasing cell size.
• Multicellular organisms grow by increasing cell number.
• Life span refers to the average duration an organism is expected to live.

Reproduction

• Living things reproduce to create offspring, necessary for the continuation of life.

Needs of Living Things

• Require a habitat such as oceans, nests, homes, or soil to sustain life.
• Living space must meet the organism's needs within its environment.
• Essential raw materials include water.

Classification of Living Things

• Organisms are classified into groups based on shared characteristics.
• Aristotle was an early classifier, dividing organisms into plants and animals, considering features like hair, leg structure, and blood presence.
• Carolus Linnaeus introduced binomial nomenclature, a two-word naming system: the first word for genus and the second for species (e.g., humans as Homo sapiens).

Taxonomy and Phylogeny

• Phylogeny is the evolutionary history of an organism, detailing changes over time.
• Six biological kingdoms include:
  • Archaebacteria
  • Eubacteria
  • Protista (protists)
  • Fungi (fungi)
  • Plantae (plants)
  • Animalia (animals/humans)

Classification Hierarchy

• Species is the smallest classification unit.
• Genus is a group of similar species.

Identification Methods

• Organisms can be identified using field guides or dichotomous keys, which provide a systematic approach to classification based on descriptive characteristics.