Chapter-1---Characteristics-and-classification-of-living-organisms

1.1 Characteristics of Living Organisms

• Core Concepts:

  • Understanding the characteristics that define living organisms is essential to biology.

  • MRS GREN acronym:

    • Movement: Action causing a change of position or place (e.g., plants growing towards the light, animals moving).

    • Respiration: Chemical reactions in cells that break down nutrient molecules to release energy (e.g., muscle contraction).

    • Sensitivity: Ability to detect and respond to internal/external changes (e.g., plants responding to gravity).

    • Growth: Permanent increase in size and dry mass (e.g., cells dividing by mitosis).

    • Reproduction: Processes making more of the same kind (e.g., asexual and sexual reproduction).

    • Excretion: Removal of waste products from metabolism (e.g., urea excreted by kidneys).

    • Nutrition: Ingestion of materials for energy, growth, and development (e.g., digestion in animals, absorption in plants).

1.2 Concept and Uses of Classification Systems

• Classification Objectives:

  • Organisms can be classified into groups according to shared features to reflect evolutionary relationships.

  • Species: Group of organisms that can reproduce to yield fertile offspring (e.g., house cats - Felis catus).

  • Binomial Naming System: Comprised of two parts, genus and species, with specific capitalization rules (e.g., Homo sapiens, Canis familiaris).

• Organizational Hierarchy:

  • From broadest to most specific:

    • Domain

    • Kingdom

    • Phylum

    • Class

    • Order

    • Family

    • Genus

    • Species

• Dichotomous Keys:

  • Tools used to identify organisms by answering a series of yes/no questions based on identifiable features.

  • Essential for classification in biology).

1.3 Features of Organisms

• Classification by Kingdom:

  • Animal Kingdom:

    • Multicellular

    • No cell wall or chloroplasts

    • Ingest solid food internally

  • Plant Kingdom:

    • Multicellular

    • Contains chloroplasts and performs photosynthesis.

    • Has a cell wall.

  • Fungi:

    • Composed of hyphae forming mycelium.

    • Absorb nutrients externally.

  • Prokaryotes:

    • Unicellular, lack a nucleus (e.g. bacteria).

  • Protoctists:

    • Unicellular, with chromosomes enclosed in a nucleus.

• Animal Classes:

  • Vertebrates:

    • Mammals, Birds, Reptiles, Amphibians, Fish.

  • Key Features:

    • Mammals: Warm-blooded, have fur, and produce milk.

    • Birds: Warm-blooded with feathers and lay eggs.

    • Fish: Cold-blooded with gills, externally fertilized eggs.

    • Reptiles: Cold-blooded with tough, leathery eggs.

    • Amphibians: Cold-blooded, live both in and out of water, and lay jelly-covered eggs.

• Arthropods Classification:

  • Insects: Six legs, segmented body, and compound eyes.

  • Arachnids: Eight legs, no antennae (e.g., spiders).

  • Crustaceans: Have exoskeletons, ten legs (e.g., crabs).

  • Myriapods: Segmented body, multiple pairs of legs (e.g., centipedes).

• Viruses:

  • Not considered living organisms as they cannot reproduce independently or carry out metabolic processes.