Biology Characteristics of Life Quiz

Characteristics of Life

• Biology is defined as the study of life and living organisms.
• Organism refers to any living thing; biotic means alive, while abiotic refers to non-living things.
• Eight key characteristics are essential for an organism to be classified as living:
  • Made of Cells: Organisms are made of complex and organized cells; the basic unit of life can be prokaryotic (without a nucleus) or eukaryotic (with a nucleus).
  • Respond to Stimuli: Organisms respond to both external (environmental) and internal (physiological) stimuli.
  • Maintain Homeostasis: Stable internal conditions are crucial; examples include thermoregulation (maintaining body temperature), pH, blood glucose, and osmoregulation (balance of water level).
  • Acquire Energy: Organisms can be autotrophic (making their own food via photosynthesis or chemosynthesis) or heterotrophic (relying on other food sources). Metabolism encompasses all chemical reactions within a cell.
  • Grow and Develop: Living organisms undergo growth but have limits on cell size and complexity, primarily through cell division.
  • Reproduce Themselves: Reproduction can be asexual (one parent) or sexual (two parents). Organisms are classified into three domains (Bacteria, Archaea, Eukarya) and several kingdoms.
  • Maintain Genetic Code: Genetic information is passed through DNA, influencing characteristics and functions.
  • Adaptation through Evolution: Organisms evolve over time to adapt to their environments.

Binomial Nomenclature

• Developed by Carolus Linnaeus, this naming system uses two words (Genus species) and is always written in Latin.
• Scientific names are italicized or underlined, with the genus capitalized and species lowercase (e.g., Homo sapiens).

Domains and Kingdoms of Life

• Life is categorized into three domains: Bacteria, Archaea, and Eukarya.
• Six kingdoms include Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia, structured hierarchy includes Phylum, Class, Order, Family, Genus, and Species.

Theory of Origins of Life

• Abiogenesis: Refers to the theory that life arose from non-living matter, where random reactions created organic molecules that led to the first living cells (protocells).
• Early Earth was anaerobic (lacking oxygen), allowing for the development of simple organic molecules and eventually self-replicating systems.

Geological Timeline

• Earth formed approximately 4.6 billion years ago; prokaryotic cell fossils date back to about 3.5 billion years ago, with eukaryotic cells appearing around 2 billion years ago.
• Life transitioned to land approximately 0.5 billion years ago.

Evolution of Photosynthesis

• The emergence of photosynthetic organisms released oxygen, which allowed for aerobic respiration, leading to more complex life forms.
• A protective ozone layer formed in response to increased atmospheric oxygen, shielding life from harmful UV radiation.

Prokaryotic and Eukaryotic Cells

• Prokaryotes: Lack a nucleus, have circular DNA, and are unicellular. Their cell walls are typically made of peptidoglycan.
• Eukaryotes: Have a nucleus and membrane-bound organelles; generally larger and can be unicellular or multicellular.

Major Groups of Life

• Eubacteria: Includes disease-causing bacteria like Escherichia coli and autotrophic cyanobacteria.
• Archaebacteria: Known for extreme living conditions; includes thermophiles and halophiles.
• Fungi: Multicellular (except yeast), heterotrophic, and decomposers with cell walls made of chitin.
• Plantae: Autotrophic and multicellular, with cellulose in their cell walls.
• Animalia: Multicellular, heterotrophic organisms without cell walls, capable of rapid responses to stimuli.

Chordates and Major Taxa

• Chordates possess characteristics such as an amniotic egg, allowing for terrestrial adaptation.
• Major groups include monotremes (egg-laying), marsupials (pouch mammals), and eutherians (placental mammals) that develop young internally.

Final Notes

• Evolution provided pathways for organisms to occupy new niches, especially following the transition to land.
• Resources for further study include educational videos by Crash Course, Amoeba Sisters, and Khan Academy for detailed explanations of these concepts.