Biology Chapter 1: Characteristics of Living Organisms

Characteristics of Life

• Responsiveness: ability to respond to external stimuli, e.g. turning off an alarm clock
• Metabolism/Energy: ingesting food and breaking it down for energy
• Reproduction: reproduction of cells and a new organism
• Materials found only in living organisms: proteins, lipids, carbohydrates, nucleic acids (DNA/RNA)
• Homeostasis: maintaining a stable internal environment, e.g. body temperature
• High degree of organization: microscopic units, cells, tissues, organs, organ systems, and individual organisms

Levels of Organization

• Chemical Level: atoms, molecules, and compounds found inside the cell
• Cellular Level: smallest unit of life, a component bounded by a membrane or cell wall
  • Specialized cells: muscle cell, nerve cell, epithelial cell, cartilage cell
• Tissue Level: assemblage of similar cells
  • Types of tissues: epithelial tissue, connective tissue, muscular tissue, nervous tissue
• Organ Level: assemblage of tissues with several functions
  • Examples: heart (cardiovascular system), liver (digestive system), kidney (urinary system), lungs (cardiovascular system)
• Organ System Level: group of organs that carries out a more generalized set of functions
  • Examples: cardiovascular system, respiratory system, digestive system, urinary system, lymphatic system, nervous system, reproductive system, endocrine system
• Organism Level: individual organisms, e.g. Homo sapiens

Taxonomy

• Definition: branch of science that deals with the study of classification based on structural similarities and common ancestry
• 3 domains and 6 kingdoms: most accepted classification system
• Kingdom: based on similar characteristics, e.g. Animalia (multicellular organisms that ingest nutrients rather than synthesize them)
• Phylum: e.g. all animals with a vertebral column or dorsal hollow notochord
• Class: e.g. Mammalia (vertebrates with placental development, mammary glands, hair or fur, and a tail located behind the anus)
• Order: e.g. Primates (mammals adapted to life in trees, with opposable thumbs)
• Family: e.g. Hominidae (primates that move primarily with bipedal locomotion)
• Genus: e.g. Homo (hominids with large brain cases or skulls)
• Species: e.g. Homo sapiens (only living organism in our species, with a unique set of combined characteristics)

Scientific Method

• Rooted in logic: if a hypothesis is wrong in even one situation, it is rejected
• Analyzing data and drawing conclusions may lead to rejecting or modifying a hypothesis

Negative and Positive Feedback

• Negative feedback: e.g. sweating (water regulation), sugar regulation
• Positive feedback: e.g. childbirth contractions (muscle contractions, uterine contractions)