Biology - Characteristics and Classification of Organisms Notes

Characteristics of Organisms

  • Definition of an Organism: A complete living thing (e.g., human, animal, plant).

  • Seven Characteristics of All Organisms:

    • Growth:
    • Organisms grow by cell division and the addition of new cells.
    • Growth can be measured as an increase in size and dry mass.
    • Movement:
    • All organisms exhibit some degree of movement, either by their own action or by movement of parts (e.g., plants can turn towards light).
    • Sensitivity:
    • Ability to detect and respond to changes in the environment (internal or external).
    • Example: Humans use ears to detect sound; plants orient toward light.
    • Excretion:
    • Removal of waste products from metabolic reactions (e.g., carbon dioxide, excess salts, and water).
    • Reproduction:
    • Ability to produce new organisms of the same species.
    • Can be sexual (involving two parents) or asexual (involving a single parent).
    • Nutrition:
    • Taking in substances from the environment for energy, growth, and development.
    • Respiration:
    • Chemical reactions that break down nutrient molecules like glucose to release energy.

Biological Classification System

  • Definition of Classification: Organizing living organisms into groups based on shared characteristics.
  • Importance of Classification: Helps understand relationships and characteristics of organisms.
  • Common Ancestor: Species that gave rise to multiple different species; all mammals share a common ancestor from about 200 million years ago.

Key Definitions

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

    • E.g., Horses (Equus caballus) and Donkeys (Equus asinus) can interbreed but produce infertile mules.

  • Binomial Naming System: A method of naming species using two words.

    • Format: Genus name (capitalized) + species name (lowercase), both in italics or underlined.
    • E.g., Bos grunniens (yaks).

Keys and Identification

  • Dichotomous Key: Tool used for identifying organisms by answering a series of questions that lead to the name of the organism.
  • How to Construct a Key:
    • List distinguishing features.
    • Create pairs of opposite statements for each feature.

Kingdoms of Life

  • Five Kingdoms:
    1. Animal Kingdom:
    • Multicellular, no cell walls, heterotrophic (consume organic substances).
    1. Plant Kingdom:
    • Multicellular, have cell walls (cellulose), autotrophic (photosynthesis).
    1. Fungi Kingdom:
    • Multicellular or unicellular, cell walls not made of cellulose, decomposers.
    1. Protoctist Kingdom:
    • Mostly unicellular, diverse characteristics (plant-like and animal-like).
    1. Prokaryote Kingdom:
    • Unicellular, no nucleus (e.g., bacteria).

Classification within Kingdoms

Animal Kingdom

  • Vertebrates: Animals with backbones (e.g., fish, amphibians, reptiles, birds, mammals).
  • Invertebrates: Animals without backbones (e.g., arthropods).

Plant Kingdom

  • Ferns vs. Flowering Plants:
    • Ferns reproduce by spores and do not produce flowers.
    • Flowering plants reproduce using flowers and seeds.

Differences in Plants:

  • Monocotyledons: One seed leaf, parallel leaf veins.
  • Dicotyledons: Two seed leaves, branched leaf veins.

Viruses

  • Non-Living Characteristics: Viruses do not display the seven characteristics of living organisms; they cannot reproduce, grow, or respond to stimuli independently.
  • Structure: Consist of genetic material surrounded by a protein coat.

Summary of Key Points

  1. All living organisms exhibit seven vital characteristics.
  2. Classification reflects evolutionary relationships based on shared features.
  3. The binomial naming system provides a universal naming convention.
  4. Each kingdom has distinct structural and functional characteristics, which help in identification and classification of organisms.
  5. Viruses are not considered living due to their lack of cellular structure and functionality.