Biological Systems: Cells to Systems

Levels of Organization

  • Biosphere → Ecosystem → Community → Population → Organism → Body System → Organ → Tissue → Cell → Molecule → Atom

Unicellular vs Multicellular Organisms

  • Unicellular: Single cell (e.g., bacteria)
  • Multicellular: Many specialized cells working together; complex organisms (e.g., plants, animals)

Cell Requirements

  • Need nutrients, oxygen
  • Waste and toxin removal
  • Stable temperature and pH regulation

Organization

  • Cells → Tissues → Organs → Systems

Plant Organization

  • Vascular Plants: Have vascular tissue for transporting water and minerals (e.g., angiosperms, gymnosperms, ferns)
  • Non-vascular Plants: No vascular tissue; simpler tissues (e.g., mosses)

Plant Tissues

  • Dermal: Outer layer; secretes cuticle (waxy film) for protection and reduced water loss
  • Ground: Interior; metabolic functions
  • Vascular: Transports water and nutrients

Plant Organs & Functions

  • Leaves: Gas exchange, photosynthesis
  • Flowers: Sexual reproduction; seeds develop after fertilization
  • Fruits: Protect seeds, aid in seed dispersal
  • Stems: Support, transport between roots and shoots
  • Roots: Absorb water/nutrients, anchor plant

Plant Systems

  • Root System: Underground; absorbs water/nutrients, provides support
  • Shoot System: Above ground; reproductive (flowers, fruit) and non-reproductive (leaves, stems) parts

Animal Cells

  • Specialized types: skin, muscle, blood, nerve, fat cells, etc.

Animal Tissues

  • Muscle: Contracts to exert force (skeletal, cardiac, smooth)
  • Nervous: Detects stimuli, transmits signals (neurons and glia)
  • Connective: Supports other tissues/organs
  • Epithelial: External/internal layers; protection, secretion, absorption

Muscle Tissue Types

  • Skeletal: Voluntary movement, attached to skeleton
  • Cardiac: Involuntary, heart muscle for pumping blood
  • Smooth: Involuntary, around organs (e.g., uterus, blood vessels)

Animal Systems & Functions

  • Digestive: Breaks down food; eliminates waste
  • Excretory: Removes waste; controls water balance
  • Endocrine: Produces/secretes hormones for regulation
  • Skeletal: Provides structure
  • Muscular: Enables movement
  • Integumentary: Protects from environment
  • Nervous: Processes sensory information
  • Immune: Defends against infection
  • Respiratory: Removes CO2CO_2, delivers oxygen
  • Blood Circulatory: Delivers oxygen/nutrients via blood
  • Reproductive: Regulates sperm/egg production, hormones, and offspring development