Biological Organization and Living Characteristics

Levels of Biological Organization

• Biological organization is a hierarchical arrangement of structures/systems
• Levels, simplest to most complex, include: organelle, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystem, and biosphere
• The cell is the smallest structural and functional unit of living organisms
• The biosphere is the largest level

Characteristics of Living Things

• Cells are the fundamental unit of structure and function (multicellular)
• Organelles are functional components within a cell
• Molecules are chemical structures of two or more atoms
• Atoms are the smallest unit of matter retaining the chemical properties of an element

Importance of Complexity

• Complexity of organization in multicellular organisms is significant because it allows for greater specification and efficiency of different cell types
• This leads to increased survival and reproductive success
• Emergence complexity/property: complex systems arise from interactions of simpler components. The properties of new materials aren't always the sum of component properties
• Integrative levels of organization consider that units of matter are organized and integrated into levels of increasing complexity

Classification of Living Things

• A classification system is like a branching tree, not a stairway to perfection
• Plants and animals have different survival strategies
• Organisms adapted to their environments are successfully adapted over time

Linnaeus Classification System

• A hierarchical system for naming/classifying all living beings, universally used by scientists
• It creates a framework for understanding relationships among species (taxa)
• Based on similarities and differences among species (Kingdoms, Phyla, Classes, Orders, Families, Genera, Species)

Importance of Classification

• Studying just one or two organisms isn't enough to know all features of a group (all kinds of organisms don't occur in one locality)
• Classifying helps in knowing relationships between different groups of organisms and evolutionary relationships

Classification Systems

• Two-Kingdom System (Linnaeus): Divided all living organisms into Plantae and Animalia
• Three-Kingdom System (Haeckel): Introduced Protista to include organisms lacking tissue differentiation (algae, fungi, protozoa)
• Four-Kingdom System (Copeland): Added Monera for bacteria and related organisms, recognizing prokaryotes (bacteria and related organisms differ from eukaryotes by having different nuclear structures)
• Five-Kingdom System (Whittaker): Included fungi as a separate kingdom from plants, using cell structure, nutrition, reproduction, thallus organization, and phylogenetic relationships as criteria
• Six-Kingdom System (Woese): Reorganized Monera into two domains (Archaea, Eubacteria) and retained the eukaryote kingdoms.

Archaebacteria, Bacteria, and Eukarya

• Archaea: prokaryotic organisms with monolayer lipid cell membranes and distinctive nucleotides
• Bacteria: typical prokaryotes lacking membrane-covered organelles and having diverse metabolic activities
• Eukarya: all eukaryotes, including kingdoms Protista, Animalia, Plantae, Fungi

Phylogeny and Cladistics

• Phylogeny is a classification using basic physical traits of organisms. It uses physical characteristics to group similar organisms. Phylogenetic trees represent evolutionary relationships.
• Cladistics hypothesizes relationships by comparing traits among species, tracing similarities to common ancestors
• Clades are groups based on shared ancestry, including ancestors and their descendants.
• Types: Monophyletic (single ancestor, all descendants), Paraphyletic (ancestor and some, but not all, descendants), Polyphyletic (no common ancestor, unrelated organisms grouped)

Characteristics of Animalia

• Have no cell walls or inorganic crystals
• Lack central vacuoles and defined growth points
• Heterotrophic nutrition (cannot make own food)
• Rapid response to external stimuli
• Have locomotion, excretory organs, nervous systems, and sense organs
• Store glycogen as reserve food

Characteristics of Plantae

• Have cell walls
• Autotrophic nutrition (make own food)
• Have a large central vacuole
• Lack excretory organs, nervous systems, sense organs, and muscular systems
• Limited locomotion (some lower algae)
• Absorb nutrients outside the organism
• Experience unlimited growth but have defined growth points
• Slow response to external stimuli
• Primary food storage is starch

Kingdom Eubacteria

• Have peptidoglycan cell walls, naked DNA, and glycogen food reserves
• Lack sap vacuoles, and have 70S ribosomes
• Include diverse bacteria, including mycoplasma, actinomycetes, rickettsiae, spirochaetes, cyanobacteria, and Firmicutes

Important Concepts

• Classification, reasons, and significance