BM

Chapter 1: Characteristics of Life, Evolution, Process of Science, and Biodiversity (Lecture Notes)

The Characteristics of Life

  • Biology is the scientific study of life.
    • Great diversity of life exists, but all living things share the same basic characteristics.
    • Living things are composed of the same chemical elements as nonliving things and obey the same physical and chemical laws that govern the universe.
    • Visual examples mentioned (bacteria, paramecium, morel, sunflower, octopus) illustrate diversity among life.
  • Life is organized into hierarchical levels.
    • The levels of biological organization range from atoms to the biosphere.
    • The cell is the basic unit of structure and function of all living things.
    • Organisms can be unicellular (single cell) or multicellular (tissue and organ systems).
    • Each higher level is more complex than the level beneath it.
    • With increasing biological complexity, new emergent properties arise at each level (new, unique characteristics not present at the previous level).
  • Levels of Biological Organization (from small to large)
    • Atom: smallest unit of an element, composed of electrons, protons, and neutrons.
    • Molecule: union of two or more atoms.
    • Cell: structural and functional unit of all living organisms.
    • Tissue: group of cells with a common structure and function.
    • Organ: composed of tissues functioning together for a specific task.
    • Organ System: several organs working together.
    • Organism: an individual; complex organisms contain organ systems.
    • Species: group of similar, interbreeding organisms.
    • Population: all members of a species in a particular area.
    • Community: interacting populations in a particular area.
    • Ecosystem: a community plus the physical environment.
    • Biosphere: regions of the Earth’s crust, waters, and atmosphere inhabited by living organisms.
  • Textbook clarification on key concepts of organization (Page references paraphrased):
    • The biosphere is the zone of air, land, and water where organisms exist.
    • An ecosystem = community + physical environment.
    • A community = interacting populations within the same environment.
    • A population = all members of a species within an area.
    • A species = group of similar, interbreeding organisms.
    • An organism = formed when organ systems are joined; organs form organ systems; tissues form organs; similar cells form tissues; molecules form larger molecules; atoms form molecules; organization of life begins with atoms.
  • Life requires materials and energy.
    • Energy is the capacity to do work and is required to maintain organization and life-sustaining chemical reactions (metabolism).
    • The sun is the ultimate energy source for nearly all life on Earth.
    • Photosynthesis in plants, algae, and some other organisms converts solar energy into chemical energy stored in carbohydrates.
    • Photosynthesis equation (conceptual): solar energy → chemical energy in carbohydrates.
  • Ecosystems: chemical cycling and energy flow
    • Chemicals are not consumed permanently; they cycle through ecosystems.
    • In a food chain, chemicals move from producers to consumers to decomposers.
    • Death and decomposition return chemicals to the environment, making them available again to living plants.
    • Energy from the sun flows through the ecosystem as one population feeds on another; there must be a constant input of solar energy.
  • Homeostasis and response to stimuli
    • Homeostasis: maintenance of internal conditions within narrow boundaries.
    • Organisms must maintain biological balance; feedback systems monitor and adjust internal conditions.
    • Living things respond to stimuli from the environment; response often involves movement.
  • Reproduction and development
    • All living organisms reproduce to maintain populations.
    • Manner of reproduction varies; genetic information (genes) is passed to the next generation.
    • Genes determine characteristics of organisms and are composed of DNA (deoxyribonucleic acid).
  • Adaptations and evolution
    • An adaptation is a modification that improves function in a particular environment.
    • Biodiversity exists because, over long periods, organisms respond to changing environments by developing new adaptations.
    • Evolution: change in a population of organisms over time, leading to greater suitability to the environment.

Evolution and the Classification of Life

  • The theory of evolution explains both the unity and diversity of life.
    • All living things descended from a common ancestor (common descent) with modification over time.
  • Natural selection (Darwin’s mechanism)
    • Environmental factors select which traits are more likely to be passed on to the next generation.
    • Individuals with favorable traits tend to produce more surviving offspring, increasing the frequency of those traits in the population.
    • Mutations introduce variation, which fuels natural selection by providing new traits.
  • Evolutionary Tree of Life
    • An evolutionary tree traces life’s ancestry back to a common ancestor, illustrating relatedness among organisms.
  • Organizing Diversity: Taxonomy vs Systematics
    • Taxonomy: identifying, naming, and classifying organisms according to rules.
    • Systematics: study of evolutionary relationships among organisms.
    • Classification categories (least inclusive to most inclusive): species → genus → family → order → class → phylum → kingdom → domain.
    • Each higher category includes more types of organisms than the preceding one.
  • Levels of Classification (illustrative, Table-like concept)
    • Domain: Archaea, Bacteria, Eukarya
    • Within Eukarya: Protista, Fungi, Plantae, Animalia
    • Example pair (illustrative): Homo sapiens (humans), Zea mays (corn)
    • Note: Some slide content indicates that kingdom designations and higher taxonomic groupings are evolving as science progresses (e.g., new supergroups and redefinitions for Protista, etc.).
  • Domains and their basic features
    • Domain Archaea: unicellular prokaryotes; live in extreme environments; adaptations to extremes; lack membrane-bound nucleus; unique biochemistry.
    • Domain Bacteria: unicellular prokaryotes; inhabit diverse environments including skin and gut; prokaryotes; lack a membrane-bound nucleus.
    • Domain Eukarya: unicellular and multicellular eukaryotes; cells contain a membrane-bound nucleus.
  • Kingdoms within Eukarya (brief features)
    • Protista: mostly single-celled or simple multicellular; algae, protozoans, slime molds, water molds; absorb, photosynthesize, or ingest food.
    • Fungi: molds, mushrooms, yeasts, ringworms; mostly multicellular filaments; absorb food.
    • Plantae: multicellular; usually contains specialized tissues; photosynthesize.
    • Animalia: multicellular; specialized tissues; absorb/ingest food (heterotrophs).
  • Kingdoms and domain updates in slide content
    • Some slides reflect ongoing taxonomy work: domain-level designations for Archaea and Bacteria; new taxonomic supergroups for Eukarya (protists, fungi, plants, animals, etc.).
  • Scientific Names: binomial nomenclature
    • Universal Latin-based naming system; two-part name.
    • First word (genus) is capitalized; second word (species designation or specific epithet) is lowercase; both words are italicized.
    • Examples: Homo sapiens, Zea mays.

The Process of Science

  • The scientific method is a standard series of steps to gain new knowledge through research.
    • Five steps typically taught: Observation, Hypothesis, Predictions and Experiments, Data Collection with Statistical Analysis, Conclusion.
  • The steps in detail
    • Observation: scientists use senses to gather information about a phenomenon.
    • Hypothesis: a tentative explanation for what was observed; example given: discovery of penicillin; developed via inductive reasoning; it must be testable.
    • Predictions and Experiments: experiments test a hypothesis; use deductive reasoning to predict outcomes; experimental design; aim to isolate the effect of a specific factor (the independent variable).
    • Data collection and analysis: data are the results of experiments; data should be observable and objective; data presentation includes tables and graphs; statistical analysis is used to interpret data.
    • Conclusion: determine whether the hypothesis is supported or refuted by the data; if predictions hold, the hypothesis is supported; if not, it is rejected; findings are reported in scientific journals and subject to peer review and replication.
  • Experimental design specifics
    • Experimental (independent) variable: the factor being tested.
    • Test group: exposed to the experimental variable.
    • Control group: goes through all aspects of the experiment but is not exposed to the experimental variable.
    • If test and control groups show the same results, the hypothesis is not supported.
  • Data and statistics
    • Data can be presented in tables or graphs.
    • Statistical analysis includes measures of variation (e.g., standard error) and assessment of statistical significance.
    • Probability value: p < 0.05 is commonly used as the threshold for statistical significance; the smaller the p-value, the greater the confidence that results are not due to chance.
  • Conclusions and dissemination
    • Conclusions interpret whether the data support the hypothesis.
    • If supported, findings contribute to scientific knowledge; if not, hypotheses are revised or rejected.
    • Findings are published in journals; peer review ensures validation; replication by others strengthens credibility.
  • Scientific Theory and Scientific Principles/Laws
    • Scientific Theory: concepts that join together two or more well-supported hypotheses; supported by a broad range of observations, experiments, and data.
    • Scientific Principle / Law: widely accepted set of theories; no serious challenges to validity.
  • Basic Theories of Biology (examples)
    • Theory (concept): Cell — All organisms are composed of cells; new cells arise only from preexisting cells.
    • Homeostasis — Internal environment stays relatively constant within protective limits.
    • Evolution — All living organisms share a common ancestor, with adaptations to diverse life strategies.
  • Example: antibiotic study framing (illustrative synthesis)
    • State/Hypothesis example: Newly discovered antibiotic B is a better treatment for ulcers than A.
    • Experimental design example: One control group (untreated), two test groups (A and B antibiotic treatments).
    • Data collection example: Endoscopy performed on all subjects to assess ulcers; statistics used to evaluate effectiveness; conclusions drawn on whether hypothesis is supported.

Challenges Facing Science

  • Science and technology definitions
    • Science: a systematic way of acquiring knowledge about the natural world.
    • Technology: application of scientific knowledge to human interests (e.g., cell phones, new drugs).
  • Biodiversity and habitat loss
    • Biodiversity: total number and relative abundance of species, genetic variability, and ecosystems in which they live.
    • Estimated global species count: up to 8.7 million; fewer than 2.3 million named and identified.
    • Extinction: death of the last member of a species or higher taxonomic category; estimated loss of hundreds of species per year due to human activities.
  • Biologically diverse ecosystems in danger
    • Tropical rain forests and coral reef ecosystems harbor many organisms and are under threat from human activities.
    • Canopy in tropical rain forests supports orchids, insects, monkeys, etc.
    • Coral reefs provide habitats for jellyfish, sponges, crabs, lobsters, sea turtles, moray eels, and fishes.
  • Destruction of healthy ecosystems and unintended consequences
    • Humans rely on healthy ecosystems for food, medicines, and raw materials.
    • Examples of ecosystem damage and consequences:
    • Draining wetlands (Mississippi and Ohio Rivers) worsens flooding and ruins farmland.
    • Destruction of South American rain forests leads to species loss and reduced lumber availability.
  • Emerging diseases
    • Recent notable emerging diseases: H5N1, H7N9, SARS, Ebola.
    • Origins of emerging diseases include:
    • New or increased exposure to insects or animals.
    • Changes in human behavior.
    • Use of technology (e.g., Legionnaires’ disease).
    • Globalization.
    • Pathogens mutating and changing hosts (e.g., avian flu).
  • Climate change
    • Climate changes are linked to human activities, including imbalanced carbon cycling.
    • More carbon is released than removed due to burning fossil fuels, deforestation, and land-use changes.
    • Increased CO2 leads to higher temperatures (global warming) via the greenhouse effect.
    • Global warming is changing Earth’s ecosystems and impacting biodiversity and ecosystem services.

Quick Reference: Key Terms and Concepts

  • Emergent properties: new characteristics at higher levels of organization that aren’t present at lower levels.
  • Metabolism: all chemical reactions in a cell.
  • Homeostasis: maintenance of internal stability within a living system.
  • Hypothesis: testable tentative explanation.
  • Independent variable: factor deliberately varied in an experiment.
  • p-value: probability of observing the data if the null hypothesis is true; significance typically set at p<0.05.
  • Binomial nomenclature: two-part Latin name, genus capitalized, species lowercase, both italicized (e.g., extit{Homo extit{ sapiens}}).
  • Three-domain system: Archaea, Bacteria, Eukarya; within Eukarya, Kingdom-level diversity includes Protista, Fungi, Plantae, Animalia (subject to ongoing taxonomic revisions).
  • Photosynthesis: process by which solar energy is converted into chemical energy stored in carbohydrates.
  • Natural selection: differential survival and reproduction based on heritable traits.
  • Biodiversity: variety and variability among living organisms and the ecosystems they inhabit.
  • Emergent issues: biodiversity loss, emerging diseases, climate change, and other challenges that influence science and society.