Themes and Concepts of Biology

Learning Objectives

  • Identify and describe the properties of life
  • Describe the levels of organization among living things
  • List examples of different sub disciplines in biology

Biology Defined

  • Biology is the science that studies life.
  • Defining life is not simple; virology studies viruses, which have some life characteristics but not all.
  • Viruses attack, cause diseases, and reproduce but don't fully meet the criteria for life.

Core Questions in Biology

  • What shared properties make something “alive”?
  • How do living things function?
  • How do we organize the diversity of life?
  • How did this diversity arise and how is it continuing?

Properties of Life

  • All living organisms share key characteristics:
    • Order
    • Sensitivity or response to stimuli
    • Reproduction
    • Adaptation
    • Growth and development
    • Regulation/Homeostasis
    • Energy processing
    • Evolution

Order

  • Organisms have highly organized structures consisting of one or more cells.
  • Single-celled organisms are complex; atoms form molecules, which form organelles.
  • Multicellular organisms have specialized cells that can perform specific functions.
  • Specialized cells form organs (e.g., heart, lung, skin).

Sensitivity or Response to Stimuli

  • Organisms respond to diverse stimuli.
  • Plants bend toward light or respond to touch.
  • Bacteria move toward or away from chemicals (chemotaxis) or light (phototaxis).
  • Movement toward a stimulus is a positive response; movement away is negative.

Reproduction

  • Single-celled organisms reproduce by duplicating DNA and dividing.
  • Multicellular organisms produce specialized reproductive cells.
  • DNA containing genes is passed to offspring, ensuring they belong to the same species and have similar characteristics as parents.

Adaptation

  • Living organisms exhibit a “fit” to their environment known as adaptation.
  • Adaptation is a result of evolution by natural selection.
  • Examples: Heat-resistant Archaea, tongue length of nectar-feeding moths.
  • Adaptations enhance reproductive potential and survival.
  • Adaptations change as the environment changes.

Growth and Development

  • Organisms grow and develop according to instructions coded for by their genes.
  • Genes direct cellular growth and development, ensuring offspring exhibit similar characteristics as parents.

Regulation/Homeostasis

  • Organisms require regulatory mechanisms to coordinate internal functions.
  • Homeostasis is maintaining a stable internal environment.
  • Organ systems perform specific functions (e.g., digestion, circulation).
  • Cells require proper temperature, pH, and chemical concentrations.
  • Organisms maintain homeostasis through regulatory mechanisms like thermoregulation.
  • Polar bears have structures to conserve heat; humans perspire to shed excess heat.

Energy Processing

  • All organisms use a source of energy for metabolic activities.
  • Some capture energy from the Sun (photosynthesis); others use chemical energy from molecules they ingest.

Evolution

  • The diversity of life results from mutations, or random changes in hereditary material over time.
  • Mutations allow adaptation to changing environments.
  • Organisms with characteristics fit for the environment have greater reproductive success via natural selection.

Levels of Organization of Living Things

  • Living things are highly organized, following a hierarchy from small to large.
    • Atom: Smallest unit of matter with element properties.
    • Molecule: Chemical structure of at least two atoms held by a chemical bond.
    • Macromolecule: Large molecules formed by combining smaller units (monomers).
      • Example: Deoxyribonucleic acid (DNA), containing instructions for an organism's function.
    • Organelles: Structures within cells performing specialized functions.
    • Cell: Smallest fundamental unit of structure and function in living organisms.
      • Viruses are not considered living because they aren't made of cells, require hijacking a living cell to reproduce.
    • Tissues: Groups of similar cells carrying out the same function.
    • Organs: Collections of tissues grouped by a common function; present in animals and plants.
    • Organ System: Functionally related organs (e.g., circulatory system).
    • Organisms: Individual living entities (e.g., a tree, single-celled prokaryotes/eukaryotes).
    • Population: All individuals of a species in a specific area (e.g., white pine trees in a forest).
    • Community: Set of populations inhabiting a particular area (e.g., trees, flowers, insects in a forest).
    • Ecosystem: Living things in an area with the non-living parts of the environment (e.g., forest with nitrogen in soil).
    • Biosphere: Collection of all ecosystems, representing zones of life on Earth.

Diversity of Life

  • Biology is broad due to the diversity of life, which arises from evolution.
  • Evolutionary biologists study the evolution of living things.
  • Carl Linnaeus proposed organizing species into a hierarchical taxonomy in the 18th century.
  • Species are grouped into a genus, similar genera into a family, and so on.
  • The current taxonomic system has eight levels: species, genus, family, order, class, phylum, kingdom, domain.

Domains of Life

  • Three domains of life: Eukarya, Archaea, and Bacteria.
    • Eukarya: Organisms with cells containing nuclei; includes fungi, plants, animals, and protists.
    • Archaea: Single-celled organisms without nuclei, many are extremophiles in harsh environments.
    • Bacteria: Another group of single-celled organisms without nuclei.
  • Archaea and Bacteria are prokaryotes (cells without nuclei).
  • The recognition that Archaea differed significantly from other bacteria led to the division of life into three domains.
  • Classifications change with new information.
  • Linnaeus also created the binomial naming system using two unique names: genus (capitalized) and species (lowercase), both italicized.
  • Every species is recognized worldwide by a unique binomial name.
    • Example: North American blue jay is known as Cyanocitta cristata; humans are Homo sapiens.

Carl Woese and the Phylogenetic Tree

  • Phylogenetic tree: A diagram showing evolutionary relationships among biological species based on genetic/physical traits.
  • Composed of branch points (nodes) and branches.
  • Internal nodes represent ancestors and points where an ancestor diverged to form new species.
  • Branch length estimates relative time.
  • Carl Woese's work in the 1970s showed life evolved along three lineages: Bacteria, Archaea, and Eukarya.
  • Woese proposed the domain as a new taxonomic level.
  • Many Archaea live under extreme conditions and are called extremophiles.
  • Woese used genetic relationships to construct his tree.
  • Woese's tree was constructed from comparative sequencing of universally distributed and conserved genes.

Branches of Biological Study

  • Biology includes many branches and subdisciplines.
    *Molecular biology: Studies biological processes at the molecular level. interactions among molecules such as DNA, RNA, and proteins, as well as the way they are regulated.
    *Microbiology: Study of the structure and function of microorganisms; includes microbial physiologists, ecologists, and geneticists. structure and function of microorganisms
    *Neurobiology: Study of the biology of the nervous system; an interdisciplinary field (neuroscience) that studies nervous system functions using molecular, cellular, developmental, medical, and computational approaches.
    *Paleontology: Uses fossils to study life’s history.
    *Zoology and Botany: Study of animals and plants, respectively.
    *Biotechnologists: Apply biological knowledge to create useful products.
    *Ecologists: Study the interactions of organisms in their environments.
    *Physiologists: Study the workings of cells, tissues and organs.

Forensic Scientist

  • Forensic science applies science to answer law-related questions.
  • Forensic scientists provide scientific evidence in courts, examining trace material associated with crimes.
  • Increased interest due to popular TV shows and molecular techniques.
  • Work involves analyzing samples like hair, blood, and DNA, processing DNA from various environments, and analyzing biological evidence like insect parts or pollen grains.
  • Requires chemistry, biology, and intensive math courses.

Scientific Ethics

  • Scientists must avoid undue damage to humans, animals, or the environment.
  • Ensure research and communications are free of bias and balance financial, legal, safety, and replicability considerations.
  • Bioethics is an evolving field where researchers collaborate to define guidelines for practice and consider new developments.

Bioethics

  • The field of Bioethics emerged after unethical practices where research subjects were not treated with dignity during biological studies.
  • One example is the Tuskegee syphilis study (1932), where African American men with syphilis were not informed or treated, decisions were made that were unjustifiable.
  • Bioethicists examine implications of gene editing technologies, balancing positive (improved therapies) and negative outcomes (displacement of organisms, “designing” humans).
  • Medical discoveries may have ethical lapses.
  • Henrietta Lacks (1951) had cervical cancer.
    • Unique immortal cells were taken without her consent.
    • HeLa cell line contributed to major medical breakthroughs.
    • Harvesting tissue from dying patients without consent is considered unethical and illegal.

Conclusion

  • Part of the role of ethics in scientific research is to examine similar issues before, during, and after research or practice takes place, as well as to adhere to established professional principles and consider the dignity and safety of all organisms involved or affected by the work
  • Knowledge of biology benefits decision-making in daily life.
  • Technology has transformed biology, allowing a better understanding of life's history, human body, origins, and survival.
  • Biologists continue to decipher mysteries, suggesting we've only begun to understand life.
  • Knowledge of biology is beneficial in any field.