Characteristics of Living Organisms

Characteristics of Living Organisms

• Growth is an increase in size, mass, and cell number.
• In unicellular organisms, growth and reproduction are synonymous, cell division increases both size and population.
• In multicellular organisms, growth involves the addition of cells and intracellular material.
• Plant growth is unlimited and continuous.
• Animal growth is limited and defined.
• Intrinsic growth (internal) is a defining property of living things.
• Extrinsic growth (external) occurs in non-living things.

Types of Growth

• Intrinsic growth is internal and irreversible, occurring in living organisms.
• Extrinsic growth is external and reversible, occurring in non-living entities such as mountains accumulating snow.
• Growth is considered a fundamental property because non-living things can exhibit it.

Reproduction Fundamentals

• Reproduction is the production of offspring similar to parents.
• Not all living organisms reproduce, for example, sterile mules and infertile human couples.
• Reproduction is a fundamental property because not all living organisms exhibit it.

Metabolic Processes

• Metabolism encompasses all chemical reactions in the body.
• All living organisms exhibit metabolism.
• No non-living things exhibit metabolism, making it a defining property.

Cellular Organization

• All living organisms are composed of at least one cell.
• Cellular organization, progressing from cells to tissues to organs to organ systems, is a defining property.

Consciousness

• Consciousness is the ability to sense the external environment and respond.
• All living beings exhibit consciousness.
• No non-living things exhibit consciousness.
• The ability to sense the environment and respond to stimuli is a defining property.

Self-Consciousness

• Self-consciousness, or awareness of oneself, is primarily observed in humans.
• Highly developed nervous and sensory systems enable humans to predict environmental changes.
• The capacity for self-consciousness makes humans aware and able to think about themselves.
• Self-consciousness, as a characteristic, is not a defining property, but a fundamental one.

Diversity in the Living World

• Species include plants, animals, and microorganisms.
• Approximately 1.7 to 1.8 billion species have been identified and described to date.
• Biodiversity refers to the distribution of plants, animals, and microorganisms on Earth.

Nomenclature

• Local names for organisms vary by region, causing confusion.
• Scientific names are standardized to avoid confusion.
• Before naming, organisms must be identified accurately.
• Nomenclature is the system of assigning names to organisms.
• Biological names consist of a scientific name.
• A scientific name is a biological name that does not change across countries or regions.

Scientific Naming Conventions

• Use guidelines provided by the International Code for Botanical Nomenclature (ICBN) for plants.
• Use guidelines provided by the International Code of Zoological Nomenclature (ICZN) for animals.

Binomial Nomenclature

• Developed by Linnaeus, provides each organism with a two-word name.
• The first word is the genus (generic name), and the second is the species (specific epithet).
• The genus name starts with a capital letter, and the species name starts with a lowercase letter.
• Scientific names are written in Latin and printed in italics.
• If handwritten, the genus and species names are underlined separately to indicate their Latin origin.

Examples of Species Naming

• Pathera leo - Lion
• Pathera tigris - Tiger
• These examples indicate that different species can share the same genus.

Examples of Plant Naming

• Ilex glabra
• Pinus glabra
• These examples indicate that different genus can share the same specific epithet.

Author Citation

• The name of the author (or a shortened form) who first described the species is written after the specific epithet.
• Example: Mangifera indica Linn. (Linn. is the abbreviation for Linnaeus)

Classification

• It involves organizing an organism based on the following:
  • Kingdom
  • Division/Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Potato Classification:
  • Kingdom: Plantae
  • Division: Angiosperm
  • Class: Dicotyledonae
  • Order: Polymoniales
  • Family: Solanaceae
  • Genus: Solanum
  • Species: tuberosum
• Classification is a multi-step process.
• Each step represents a category (or taxon).
• The smallest unit is the species, and the largest unit is the kingdom.

Taxonomic Categories

• Total real categories: 7
• Intermediate categories: Subfamily, suborder, subclass
• Categories represent the taxon.

Taxonomic Hierarchy

• The ascending order of taxonomic categories is from species to kingdom.
• This is known as the taxonomic hierarchy.

Suffices

• Suffixes are used to identify taxonomic categories.
  • -aceae: Family (e.g., Solanaceae, Poaceae, Liliaceae)
  • -ales: Order (e.g., Polymoniales, Poales, Sapindales)
  • -ae: Class (e.g., Dicotyledonae)
  • -phyta: Division (e.g., Chlorophyta)
• Taxa are always different.

Taxonomic Levels

• Levels are the levels from species to kingdom or vice versa.
• Example:
  • Wheat, maize, and rice are at the same level (species).
  • Animal (kingdom), mammal (class), and dog (species) are at different levels.

Taxonomy

• Involves characterization, identification, classification, and nomenclature of living organisms.
• Taxonomy is based on characteristics.

Classical Taxonomy

• Based on morphological and external characters.

Modern Taxonomy

• Includes both external and internal characters.
• Includes cell structure, development process, and ecological information.

Systematics

• Systematic arrangement of organisms.
• Includes evolutionary relationship.
• Taxonomy + Phylogeny = Systematics
• Systematics includes Taxonomy and Phylogeny.
• Phylogeny concerns the evolutionary history of an organism.
• Linnaeus wrote the book Systema Naturae, which included scientific names of animals.
• Early classifications were based on the use of organisms (economic importance).

Species

• The most basic unit of classification.
• John Ray introduced the term species.
• Ernst Mayr defined the biological concept of species: individuals that can interbreed are considered the same species.
• Individuals within a species show fundamental similarities.
• Example
  • Solanum tuberosum (potato)
  • Solanum melongena (brinjal/eggplant)
  • Solanum nigrum (black nightshade)
• All share the genus Solanum.
• Different species can share the same genus.

Genus

• A group of related species that share similarities.
• Species within a genus are more related to each other compared to species in different genera.
• Examples
  • Felis catus (domestic cat)
  • is in the genus Felis.
  • The genus Panthera is polytypic (having more than one species)
  • The genus Homo with only one species, Homo sapiens, is monotypic.

Order

• A group of related families.
• Family is determined by vegetative and reproductive characteristics.
• Example:
  • Separate families, such as Convolvulaceae (sweet potato family) and Solanaceae (potato family) are both placed in the same order, Polymoniales.
• Mammal examples:
  • The families Felidae (cats) and Canidae (dogs) are placed in the same order, Carnivora.

Hierarchy

• As you move from species to kingdom, the number of shared characteristics decreases.
• Taxonomic classification becomes more complex with fewer similarities.
• Species have maximum similarities, while the kingdom has minimal similarities.

Identification

• Easier and more accurate classification is achieved when there are more similarities at lower levels.
• Complexities in classifications arise when similarities are minimal.

Division/Phylum

• Groupings that are the next level up from class.
• Example: Classes Dicotyledonae and Monocotyledonae grouped under the division Angiospermae in plants.

Key Features

• The key features used in animals include a notochord and dorsal hollow neural system.
• The key feature used by plants include containing cell walls.

Kingdom

• Plant kingdom
• Animal kingdom