Biology: Characteristics of Living Things and Evolution

Characteristics of Living Things

• All living organisms are composed of one or more cells, the basic unit of life.
• All living forms carry deoxyribonucleic acid (DNA), the genetic blueprint.
• Organisms obtain and utilize energy from their environment.
• Reproduction is a fundamental characteristic; organisms pass genetic information to offspring.
• Living things respond to environmental stimuli to adapt and survive.
• Homeostasis is maintained to regulate internal balance despite external changes.
• Growth and development occur in all organisms throughout their life cycles.

Evolution

• Evolution is the gradual process by which new species originate from ancestral species.
• Carl Linnaeus pioneered hierarchical taxonomy in the 18th century.
• Biological evolution indicates that all life shares a common ancestor.
• Descent with modification leads to the diversity of species documented in the fossil record.

Mechanisms of Evolution

• Natural Selection: Advantageous traits are favored, enhancing survival and reproduction.
• Mutation: DNA changes in parents can affect offspring traits, impacting allele frequencies.
• Genetic Drift: Random changes in allele frequency can occur in small populations.
• Gene Flow: Movement of genes between populations alters genetic diversity.
• Non-Random Mating: Preferences in mating partners result in favored traits becoming more common in future generations.

Taxonomy and Systematics

• Taxonomy classifies and names living organisms (nomenclature).
• Systematics involves understanding evolutionary relationships (phylogenetics) among species.

Binomial Nomenclature

• Each organism has a two-part Latin name consisting of genus and species.
• Genus starts with a capital letter, species in lowercase; both are italicized or underlined when handwritten.
• Examples include:
  • Homo sapiens (Humans)
  • Helianthus annuus (Sunflower)
  • Panthera tigris (Tiger)
  • Mangifera indica (Mango)
  • Canis familiaris (Dog)

Domains of Life

• Three domains exist: Eukarya, Archaea, Bacteria.
  • Eukarya: Includes complex organisms with cells containing nuclei.
  • Archaea: Comprises single-celled organisms that often inhabit extreme environments.
  • Bacteria: Characterized by single-celled organisms without nuclei.

Kingdom Classification

• Carolus Linnaeus introduced the two-kingdom system: Plantae and Animalia.
• Robert Whittaker expanded this to five kingdoms: Plantae, Animalia, Monera, Protista, Fungi.

Kingdom Details

• Kingdom Monera: Prokaryotic, unicellular organisms; divided into Archaebacteria and Eubacteria.
• Kingdom Protista: Eukaryotic organisms, can be unicellular or multicellular; includes various protists such as protozoans and algae.
• Kingdom Fungi: Eukaryotic, heterotrophic organisms; generally multicellular with hyphae, which are long thread-like structures.
• Kingdom Plantae: Eukaryotic, multicellular, autotrophic organisms; classified into vascular and non-vascular plants.
• Kingdom Animalia: Eukaryotic, multicellular, heterotrophic organisms; includes invertebrates and vertebrates based on the presence of a notochord.

Overview of Animal Classification

• Invertebrates: Animals without a backbone, including Porifera (sponges) and Cnidarians (jellyfish).
• Vertebrates: Animals with a backbone, categorized into fishes, amphibians, reptiles, birds, and mammals, each with distinct characteristics.

Summary of Kingdom Traits

• Monera: Prokaryotic, unicellular, can be autotrophic or heterotrophic.
• Protista: Eukaryotic, both unicellular and multicellular, includes various nutritional modes.
• Fungi: Eukaryotic, multicellular or unicellular, heterotrophic, primarily via spores.
• Plantae: Eukaryotic, multicellular, autotrophic with cellulose-based cell walls.
• Animalia: Eukaryotic, multicellular, heterotrophic, derived from fertilized gametes.