What is like?

Properties of Life

  • By the end of this section, students will be able to:

    • Identify and describe the properties of life.

    • Describe the levels of organization among living things.

    • List examples of different sub-disciplines in biology.

Definition of Biology

  • Biology is defined as the science that studies life.

  • Despite sounding simple, defining life is complex and challenging.

  • Example of Complexity:

    • Virology studies viruses, which display some characteristics of life but lack others necessary for a complete definition.

Characteristics of Viruses

  • Viruses can:

    • Infect living organisms.

    • Cause diseases.

    • Reproduce, but only within a host cell.

  • **Controversy in Definitions:

    • Some biologists argue viruses are alive due to their RNA/DNA and ability to reproduce using a host.

    • Others argue that viruses fall short of essential criteria for life, invoking prions as an example.**

Four Fundamental Biological Questions

  1. What are the shared properties that make something alive?

  2. How do living things function?

  3. How do diverse living organisms get organized for better understanding?

  4. How did biological diversity arise, and how does it continue to develop?

  • Biologists strive to solve and progress in these areas through ongoing discovery.

Key Characteristics of Living Organisms

  • There are eight primary characteristics that define life:

    1. Order - Highly organized structures.

    2. Sensitivity/Response to Stimuli - Organisms respond to environmental stimuli.

    • Examples:

      • Plants bending towards light (phototropism).

      • Bacteria moving towards or away from chemicals (chemotaxis).

    1. Reproduction - Capable of producing offspring, ensuring genetic material is passed to the next generation.

    • Single-celled organisms reproduce by DNA duplication followed by division.

    • Multicellular organisms produce specialized reproductive cells.

    1. Adaptation - Evolutionary capacity to adjust to the environment.

    • Adaptations enhance survival and reproductive success.

    • Examples include extremophiles and specific morphological traits.

    1. Growth and Development - Growth follows genetic instructions coded in DNA.

    • Ensures offspring develop characteristics similar to their parents.

    1. Regulation - Mechanisms to coordinate internal functioning, including nutrient transport and response to stress.

    • Examples include organ systems like the digestive and circulatory systems.

    1. Homeostasis - Ability to maintain stable internal conditions despite external fluctuations.

    • Thermoregulation in polar bears vs. heat regulation in humans.

    • Blood pH regulation showcases homeostasis.

    1. Energy Processing - All organisms require energy for metabolic activities.

    • Organisms may capture energy from the sun (photosynthesis) or consume chemical energy (cellular respiration).

Levels of Organization in Living Things

  • Living organisms are organized hierarchically from smallest to largest:

    1. Atoms - Smallest unit of matter, consisting of protons, neutrons, and electrons.

    2. Molecules - Chemical structures formed by atoms.

    • Includes macromolecules like DNA.

    1. Cells - Smallest unit of life; can be single-celled or multicellular.

    • Cells can be classified as:

      • Prokaryotic - Single-celled without membrane-bound organelles (e.g., bacteria, archaea).

      • Eukaryotic - Cells with membrane-bound organelles and nuclei.

    1. Tissues - Groups of similar cells performing a common function.

    2. Organs - Structures composed of different tissues.

    3. Organ Systems - Groups of related organs working together.

    4. Organisms - Individual living entities, including plants, animals, and microorganisms.

    5. Populations - Groups of individuals of the same species in a specific area.

    6. Communities - Consist of different populations interacting in a shared environment.

    7. Ecosystems - Comprised of living organisms and their nonliving environments.

    8. Biosphere - Global collection of all ecosystems, encompassing land, water, and atmosphere.

Largest and Smallest Organisms

  • Smallest Organism: Mycoplasma genitalium, measuring approximately 200 to 300 nanometers.

  • Largest Organism: Honey fungus, which can extend over 2.4 miles in Oregon.

Diversity of Life

  • Biology encompasses tremendous diversity, arising from evolutionary processes that lead to new species.

  • Carl Linnaeus:

    • Proposed a hierarchical taxonomy to classify known species.

    • Organized species from specific (species) to general (domain): species, genus, family, order, class, phylum, kingdom, domain.

Taxonomic Hierarchy

  • Current taxonomic system includes:

    • Domains: Eukarya, Archaea, and Bacteria.

    • Domain Eukarya includes all organisms with nuclei and includes kingdoms such as fungi, plants, and animals.

    • Archaea and bacteria are prokaryotes, characterized by their lack of nuclear membranes.

  • Binomial Naming System:

    • Developed by Linnaeus to provide unique names to species, consisting of genus (capitalized) and species (lowercase), in italics.

    • Example of species naming: North American blue jay - Cyanocitta cristata, humans - Homo sapiens.

Phylogenetic Relationships

  • Phylogenetic tree: Diagram showing evolutionary relationships based on genetic similarities.

    • Composed of branches and nodes representing common ancestors.

    • Length of branches can indicate evolutionary time scales.

  • Shift from five kingdoms to three classified domains (Bacteria, Archaea, Eukarya) due to advances in genetic understanding.

Sub-disciplines in Biology

  • The breadth of biology leads to various branches:

    • Molecular Biology - Studies biological processes at the molecular level.

    • Microbiology - Focuses on microorganisms, including their structure and function.

    • Neurobiology - Examines the biology of the nervous system, recognized as part of neuroscience.

    • Paleontology - Uses fossils to investigate life's history.

    • Zoology and Botany - Concerning animal and plant studies, respectively.

    • Ecology - Explores interactions among organisms and their environments.

    • Physiology - Studies the functions of cells and systems in living organisms.

    • Forensic Science - Applies scientific principles to legal questions.

Conclusion

  • The understanding of biology enhances personal decision-making regarding health, food sources, and ecological benefits.

  • Advancements in technology, particularly in genetics, continue to reshape biology and provide insights into the history of life and human survival strategies.

  • Ongoing research urges a continual reassessment of biological knowledge and its implications for the future of life on Earth.