1. CLASSIFICATION AND CHARACTERISTICS OF LIVING ORGANISM

Characteristics of Living Organisms

Growth = A permanent increase in size.

  • Organisms start small and grow larger.

    Growth occurs through the expansion of existing cells and the addition of new cells.

Movement = An action by an organism causing a change of position or place.

  • All organisms can move to some extent.

    Most animals move their entire bodies, while plants can move parts gradually.

Sensitivity = The ability to detect and respond to changes in the environment.

  • Organisms collect information about environmental changes and react accordingly.

Excretion = The removal of toxic materials and excess substances.

  • Organisms produce unwanted waste products through metabolic reactions; therefore, removal from the body is necessary.

Reproduction = Processes that create more organisms of the same kind.

  • Organisms can produce new individuals of their own species.

Nutrition = The intake of materials for energy, growth, and development.

  • Organisms consume substances from their environment to provide energy and resources for cell creation.

Respiration = The chemical reactions in cells that break down nutrient molecules and release energy.

  • All organisms break down substances such as glucose within cells to harness usable energy.

Classification of Living Organisms

Classification system helps to categorize organisms into distinct kingdoms and groups.

The Kingdoms of Living Organisms

  • Major kingdoms include:

    • Plants

    • Animals

    • Fungi

    • Protoctista

    • Prokaryotes (Eubacteria)

    • Archaea (Archaebacteria)

Characteristics of Key Organism Groups

  • Plants:

    • Multicellular; have cell walls made of cellulose; perform photosynthesis.

  • Animals:

    • Multicellular; no cell walls; consume organic materials.

  • Fungi:

    • Mostly multicellular; cell walls are not cellulose-based; often saprophytic or parasitic feeders.

  • Protoctista:

    • Unicellular or multicellular; diverse feeding methods.

  • Prokaryotes (Eubacteria):

    • Unicellular; lack nuclei and mitochondria; have cell walls.

Taxonomy and Scientific Naming

  • Species: Group of organisms that can reproduce and produce fertile offspring.

  • Genus: Contains several species with similar characteristics.

  • Scientific naming follows the binomial system, e.g., Panthera leo (lion) or Homo sapiens (humans).

Binomial Naming System

  • An internationally agreed system consisting of two parts: the name of the genus and the name of the species.

  • Proper names are printed in italics.

    • Example:

      • Equus caballus (horse)

      • Canis lupus (wolf)

Viruses

  • Viruses cannot be classified as living things: do not move, feed, excrete, show sensitivity, grow, or reproduce independently.

  • Structure: Composed of a piece of DNA or RNA surrounded by a protein coat. They only replicate inside a living cell.

Prokaryotic Characteristics

  • Prokaryotes: Bacteria with characteristics including:

    • No nucleus, no mitochondria, cell walls, and circular DNA/plasmid.

Classification of Animals and Plants

  • The animal kingdom broadly categorizes organisms based on shared features, such as vertebrates and their distinct classes: fish, amphibians, reptiles, birds, and mammals. Vertebrates share common characteristics like a backbone, but display varied adaptations for survival in different environments.

    Examples of Vertebrate Classes:

    • Fish: Largely aquatic, gilled organisms with fins.

    • Amphibians: Such as frogs, transition between aquatic and terrestrial life with gilled larvae and lung-breathing adults.

    • Reptiles: Cold-blooded vertebrates with scaly skin.

    • Birds: Endothermic vertebrates with feathers and wings.

    • Mammals: Warm-blooded vertebrates that nurture their young with milk.

    In plants, flowering plants reproduce by seeds encased in flowers, while ferns reproduce through spores.

    Differences within Flowering Plants:

    • Monocotyledonous Plants: Have a single cotyledon in their seeds and a branched root system.

    • Dicotyledonous Plants: Possess two cotyledons in their seeds, often featuring a tap root system.

    Dichotomous Keys

    A method for classifying organisms is through dichotomous keys, which involve a series of paired statements that guide the user towards identifying an unknown organism.