Chapter 1 - Characteristics and Classification of Living Organisms

Characteristics of Living Organisms

  • Movement:

    • Living organisms exhibit movement, either locomotion or internal movements, often in response to stimuli.

  • Reproduction:

    • All living organisms have the capability to reproduce, either sexually or asexually, ensuring the continuation of their species.

  • Respiration:

    • Involves chemical reactions in cells that break down nutrients to release energy.

    • Chemical reactions in cells break down nutrients to release energy. Aerobic respiration equation: C6H12O6+6O2→6CO2+6H2O+EnergyC6H12O6+6O2→6CO2+6H2O+Energy.

    • Anaerobic respiration occurs in the absence of oxygen, producing lactic acid in animals and ethanol and carbon dioxide in plants. Aerobic respiration is more efficient, yielding up to 38 molecules of ATP per glucose molecule, while anaerobic respiration yields only 2 ATP.

  • Sensitivity:

    • Ability to detect and respond to environmental changes.

    • This response is crucial for maintaining homeostasis and enables organisms to adapt to their surroundings effectively.

  • Growth:

    • Permanent increase in size and complexity, involving new cells and enlargement of existing cells.

  • Nutrition:

    • Intake of materials for energy, growth, and repair.

    • Can be autotrophic or heterotrophic.

  • Excretion:

    • Removal of waste products from metabolic reactions.

  • Viruses:

    • Not classified as living because they cannot complete these processes independently.

    • require a host cell to replicate.

Classification Systems

  • Organisms classified by shared features, reflecting evolutionary relationships.

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

  • Binomial System: Internationally agreed system for naming species (Genus species).

  • Classification uses morphology, anatomy, and genetic data (DNA sequences).

  • Taxonomy: The science of classifying organisms into hierarchical categories, including domain, kingdom, phylum, class, order, family, genus, and species.

Classification Keys

  • Dichotomous keys used to identify and classify living things through paired questions.

  • Morphological characters: Structural features of organisms, such as shape and size, are utilized in identification.

Why Classify?

  • Simplifies study and conservation.

  • Explores relationships.

  • Facilitates communication.

  • Aids in understanding evolution.

Carl Linnaeus

  • Developed binomial naming and hierarchical classification.

  • Seven levels: Kingdom, Phylum, Class, Order, Family, Genus, Species.

  • Charles Darwin - Proposed the theory of natural selection as a mechanism for evolution, emphasizing adaptation and survival of the fittest.

Five Kingdoms Classification

  • Monera: Prokaryotic, unicellular (e.g., bacteria).

  • Protista: Eukaryotic, unicellular or multicellular (e.g., algae, protozoans).

  • Fungi: Eukaryotic, multicellular, absorb nutrients (e.g., mushrooms, yeast).

  • Plantae: Eukaryotic, multicellular, photosynthesize (e.g., trees, moss).

  • Animalia: Eukaryotic, multicellular, ingest food (e.g., insects, mammals).

Fungi

  • Body organized into mycelium of hyphae; cell walls made of chitin.

  • Feed by extracellular secretion of digestive enzymes. (Extracellular digestion)

Plants

  • Multicellular organisms with chloroplasts for photosynthesis; cellulose cell walls.

Animals

  • Multicellular

  • Cannot photosynthesize

  • No cell walls

  • Have nervous systems

  • Store carbohydrates as glycogen.

Invertebrates

  • Lack a backbone; vary in digestive and nervous systems.

Vertebrates (Phylum Chordata)

  • Fish: Cold-blooded, have gills, scales, and fins.

  • Amphibians: Cold-blooded, have gills and lungs, thin moist skin, lay jelly-like eggs.

  • Reptiles: Cold-blooded, have lungs, scales, lay leathery eggs.

  • Birds (Aves): Warm-blooded, have lungs, feathers, lay hard eggs.

  • Mammals: Warm-blooded, have lungs, hair, mammary glands, live birth.

Amphibians vs Reptiles

  • Amphibians: Born with gills, thin moist skin, lay jelly-like eggs, undergo metamorphosis.

  • Reptiles: Born with lungs, scales and dry skin, lay leathery eggs with shells, hatchlings look like adults.

Protoctist & Prokaryotes

*Protoctist: unicellular organism that has a nucleus.
*Prokaryotes: Single-celled, no nucleus or membrane-bound organelles

Viruses

  • Non-cellular, consist of genetic material (DNA or RNA) surrounded by a protein coat.

  • Parasitic, reproduce within living cells.